Sexual rivalry may drive frog reproductive behaviors

It may be hard to imagine competing over who gets to kiss a frog, but when it comes to mating, a new study concludes that some frogs have moved out of the pond onto land to make it easier for the male in the pair to give sexual rivals the slip.

Biologists have long thought that some frog species evolved to mate on land — sometimes in unusual places — instead of in open water to better guard eggs and tadpoles from easily being eaten by fish and other predators. But the new research by a team of U.S. and Brazilian frog biologists suggests that mating on land in many species might in part be a strategy that male frogs use to ensure that their own DNA gets passed on, instead of the DNA of their rivals. Sexual selection may trump natural selection in the evolution of these reproductive behaviors, according to the new study, to be published online ahead of print on July 26 in The American Naturalist.

Frogs have a “dizzying array” of reproductive strategies, according to Rayna Camille Bell, a UC Berkeley postdoctoral fellow who contributed to data collection, analyzed and interpreted much of the data, and helped co-author the study, which was led by her doctoral thesis advisor, Kelly Zamudio, a professor at Cornell University.

Mating in frogs typically involves the male wrapping his arms around the female, the female depositing eggs and the male fertilizing the eggs, which will hatch into tadpoles and ultimately develop into froglets. The earliest frogs completed all of these steps in water, but among different frog species there are various strategies for accomplishing these reproductive tasks before a new generation hops or swims off on its own. Frog species vary in where they mate, where they lay eggs, where tadpoles develop and whether and how eggs and tadpoles are tended to by parent frogs. Some species even skip the egg stage, giving birth to live tadpoles or even froglets.

“Biologists noticed an apparent linear progression toward more terrestrial reproduction throughout frog evolution and proposed that frogs avoid putting their eggs and tadpoles in streams or ponds because they would be more vulnerable to aquatic predators,” Bell said. The apparent trend toward increasingly terrestrial reproduction is most evident in tropical frogs, perhaps because more humid environments more easily permit reproduction on land without eggs or tadpoles drying up.

But eggs and tadpoles are still susceptible to predators on land, and biologists haven’t reached a consensus on why so many tropical frog species have terrestrial reproductive modes. If natural selection to minimize aquatic predation on developing eggs and tadpoles was the main driver for evolving terrestrial reproduction, Bell and her collaborators reasoned, there should be equally diverse strategies for placing both eggs and tadpoles out of harm’s way.

But in reviewing datasets built upon the field work of other biologists and their own data on hundreds of species in two different families of tropical frogs, the Hylidae and Leptodactylidae, the researchers found that this was not generally the case.

They found that most of the diversity in reproductive strategies involves the egg stage. Even when eggs are deposited on land, tadpoles often quickly end up in dangerous waters, falling off a leaf into a stream, for instance. This pattern indicates that selection is acting independently on eggs versus tadpoles, Bell said, suggesting that there might be other evolutionary advantages of depositing eggs on land.

“Besides avoiding aquatic predators, the benefit of depositing your eggs on land away from the main body of water — if you are a male frog — is that you get the female away from the breeding frenzy where there are hundreds of males all competing for access to females,” Bell said. “On land, it’s easier to make sure that no other male is moving in on your female and fertilizing her eggs.”

Bell and co-authors found that when mating occurs away from the main body of water, the mating site is often more private and hidden from competing males. Some frog species mate in the water-containing folds of bromeliad leaves, for example, and males in other species even build volcano-shaped mud nests that they may guard while mating.

The researchers hypothesized that if sexual selection is playing a role in the evolution of these mating behaviors, then in species where competition for fertilizing eggs is fierce males should have larger sperm-producing testes, similar to what has been observed in other animals where male competition for mates is intense. Conversely, males in species with private breeding sites should have smaller testes.

Indeed, Bell and colleagues determined that the mass of male testes, which is a proxy for sperm competition, is smaller and less variable in frogs that hide while breeding, indicating they are less vulnerable to other males horning in.

What is special about the tropics?

Most studies of frog mating systems have been in temperate regions. Like this study, new natural history data on mating systems and reproductive modes in both temperate and tropical frog species are likely to challenge preconceived notions of how and why these complex reproductive behaviors evolved, Bell said.

“The tropics have the greatest frog species diversity, as well as the most diversity and complexity in frog reproductive modes,” Bell said, “But we know the least about the biology, behavior and diversity of these tropical species, even though many are threatened, and some are only now being discovered for the first time. Hopefully our study will draw attention to how much we still have to learn about sexual selection and mating system dynamics in frogs.”  Science Daily Original web page at Science Daily


Deadly fungus threatens African frogs

Misty mountains, glistening forests and blue-green lakes make Cameroon, the wettest part of Africa, a tropical wonderland for amphibians.

The country holds more than half the species living on the continent, including dozens of endemic frogs — an animal that has been under attack across the world by the pervasive chytrid fungus (Batrachochytrium dendrobatidis). Africa has been mostly spared from the deadly and rampant pathogen that wiped out entire species in Australia, Madagascar and Panama, until now.

University of Florida herpetologist David Blackburn and colleagues at the Museum für Naturkunde in Berlin have documented declines in frog species on Cameroon’s Mount Oku and Mount Manengouba over a span of more than 12 years. The scientists link the decline of at least five species of frogs found only in these mountains to chytrid, which may have been exacerbated by habitat destruction, pollution and climate change resulting in weaker and more susceptible frogs, said Blackburn, an associate curator of herpetology at the Florida Museum of Natural History on the UF campus.

“There’s been this perception that frogs in Africa are not affected by chytrid at all, but we have evidence of the disease in some animals,” said Blackburn, co-author of a new study appearing online this week in PLOS ONE. “This is the first real case of a decline across multiple amphibian species in Africa.”

Study scientists collected and documented abundance and diversity of frog species living on the two mountains before and after the immergence of chytrid in the area between 2008-2010. The persistent pestilence latches onto the frog’s skin and can spread internally to the animal’s organs, quickly leading to death.

Blackburn said many of the once common species, like the bright red Cardioglossa manengouba, a frog he discovered and named during graduate fieldwork in the early 2000s, are now scarce and nearly impossible to find.

“It’s looking like some of these frogs may not be around by the time my kids are old enough for me to take them to Cameroon to see them,” he said.

While chytrid is to blame for most of the patterns of decline in frogs worldwide, Blackburn said scientists have linked the fungus to climate change, which may drive the emergence of chytrid in some places.

In studies exploring declines of amphibians in Latin America, University of South Florida herpetologist Jason Rohr has shown that unpredictable climate fluctuations associated with climate change can increase chytrid-related die-offs.

“Our research has shown there may be an underappreciated link between climate change, disease and biodiversity losses,” Rohr said. “Global warming and the severity of unpredictable variations in temperature increase chytrid growth on amphibians.”

Blackburn said extreme temperature changes may affect the biology of the frogs by making them more, or less, susceptible to pathogens. He said this could easily be a factor in Cameroon, though he and colleagues have not yet collected enough data to make that call.

In captivity, frogs with chytrid are treated with an effective fungicide bath. In the Sierra Mountains of California, scientists have successfully released frogs inoculated with bacteria that make them less vulnerable to chytrid. But these methods are less practical in the mountains of Cameroon.

“Even if a cure was found, it would be hard to inoculate all of the individual frogs out there,” Backburn said. “Promoting a healthier environment in general for Africa’s amphibians in terms of water quality and habitat protection is our best shot for keeping these species around.”  Science Daily  Original web page at Science Daily


Tunnel through the head: Internally coupled ears enable directional hearing in animals

Humans use the time delay between the arrival of a sound wave at each ear to discern the direction of the source. In frogs, lizards and birds the distance between the ears is too small. However, they have a cavity connecting the eardrums, in which internal and external sound waves are superimposed. Using a universal mathematical model, researchers at the Technical University of Munich (TUM) have now for the first time shown how new signals are created in this “inner ear” used by animals for localizing sounds.

Whether perceiving an encroaching predator or finding prey in the dark, precisely localizing the source of a sound is indispensable in the animal kingdom. Almost all mammals, including humans, localize sound sources horizontally via the the delay in time in which sound signals arrive at each ear. Using this time difference the brain can calculate the direction from which the sound emanated.

Frogs, many reptiles and birds do not have this option since the distance between their ears often measures merely a few centimeters. The time difference is thus so small that it cannot be processed by the brain. To make up for this disadvantage theses animals have developed a simple albeit very effective system: An air-filled cavity connects the eardrums of the two ears.

This cavity, which runs right through the head, couples the eardrums. The scientists refer to this as “internally coupled ears” or ICE. This “tunnel in the head” is clearly visible when light falls into one ear of a gecko: The light then shines out of the other ear.

Unlike humans, the animals perceive not only external signals, but also a superposition of external sound waves with those that are created internally through the coupling of the two sides. Scientists have determined in experiments that animals use the resulting signals for pinpointing sound sources. But what exactly happens in the coupled ears remained a mystery.

Now, scientists working led by Leo van Hemmen, Professor of Theoretical Biophysics at the Technical University of Munich (TUM) have for the first time developed an universal mathematical model that describes how sound waves propagate through the internally coupled ears and which clues for localizing sound sources are created in the process.

“Our model is applicable to all animals with this kind of hearing system, regardless that the cavities between the eardrums of the various species look very different,” explains van Hemmen. “We now understand what exactly happens inside the ears of these animals and can both explain and predict the results of experiments in all sorts of animals.” Over 15,000 species have internally coupled ears — that is more than half of all land-dwelling vertebrate animals.

Using their model, van Hemmen and his team discovered that the animals have even developed two different methods of hearing with internally coupled ears. They occur in different frequency domains and augment each other.

In sounds below the fundamental frequency of the eardrum the time difference in the superposition of the internal and external signals is amplified up to five-fold. That is sufficient to facilitate sound localization.

In higher frequencies the time difference can no longer be evaluated. Here, another property of the signal becomes relevant: The difference in the amplitude, i.e. the loudness, of the sound perceived by the ears. “The amplitude difference occurs solely through the coupling of the two ears,” explains van Hemmen. “That was a surprising result.”

This new insight on the mechanisms and especially the advantages of hearing with internally coupled ears is also relevant for industrial applications. It is conceivable that robots will be equipped with this kind of hearing system. “I can very well imagine applications in robotics, because this kind of amplification doesn’t need energy” expresses van Hemmen. In the future van Hemmen and his team of scientists hope to refine their model in collaboration with the experimental work of colleagues. Science Daily  Original web page at Science Daily


Brazilian torrent frogs communicate using sophisticated audio, visual signals

Brazilian torrent frogs may use sophisticated audio and visual signals to communicate, including inflating vocal sacs, squealing, and arm waving, according to a study published January 13, 2016 in the open-access journal PLOS ONE by Fábio P. de Sá, Universidade Estadual Paulista, Brazil, and colleagues.

Frog communication plays a role in species recognition and recognition of potential rivals or mates. The authors of this study investigated communication in the Brazilian torrent frog, an endemic frog to Brazil a frog endemic to Brazil, where males are known to be territorial and display elaborate courtship behavior. The researchers observed nearly 70 male and female torrent frogs over a period of 15 months.

The researchers observed a complex repertoire of acoustic and visual displays during advertisement, including long-range, short-range, and courtship communication with other frogs. During courtship, the authors observed males performing visual displays using their toes, feet, hands, legs, arms, vocal sacs, head, and body while females only displayed hand, arm, and body movements. They also describe a behavior previously unknown in frogs, where females use a combination of visual displays and touch to stimulate the male’s courtship call. They also found that frogs may choose to signal with their left or right limbs, and that males can choose which of their two vocal sacs to use for visual signaling. Torrent frogs also exhibit a diverse acoustic repertoire that, besides the advertisement call, include peeps, squeals, and courtship calls.

The authors suggest their results indicate that Brazilian torrent frogs have one of the most diverse repertoires of visual and audio displays known to frogs, indicating that communication in torrent frog species is likely more sophisticated than previously thought.

Dr. Fábio P. de Sá adds “Our study indicates that communication in species of the genus Hylodes is more sophisticated than expected. Also we suggest that communication in frogs is more complex than thought. Likely, that is particularly true for tropical areas, where there is a higher number of species and phylogenetic groups and/or where there is higher microhabitat diversity.”  Science Daily  Original web page at Science Daily


Invasive amphibian fungus could threaten U.S. salamander populations

A deadly fungus causing population crashes in wild European salamanders could emerge in the United States and threaten already declining amphibians, according to a report released today by the U.S. Geological Survey.

The Department of the Interior is working proactively to protect the nation’s amphibians. The USG report released today highlights cooperative research and management efforts needed to develop and implement effective pre-invasion and post-invasion disease-management strategies if Batrachochytrium salamandrivorans (Bsal) enters and affects salamanders within the United States. Last week the United States Fish and Wildlife Service published a rule listing 201 salamander species as injurious under the Lacey Act, which will reduce the likelihood of introduction of Bsal into the country.

Although Bsal has not yet been found in wild U.S. salamander populations, scientists caution it is likely to emerge here because of the popularity of captive salamanders as household pets, in classrooms and in zoos; the captive amphibian trade is a known source of salamanders afflicted with the fungus.

Amphibians are the most endangered groups of vertebrates worldwide, with another fungus closely related to Bsal (Bd) contributing to amphibian die-offs and extinctions global over the last two decades.

“Based on the kinds of species affected and the fact that the United States has the highest salamander diversity in the world, this new pathogen is a major threat with the potential to exacerbate already severe amphibian declines,” said Evan Grant, a USGS wildlife biologist and lead author of the USGS report. “We have the unusual opportunity to develop and apply preventative management actions in advance.”

Bsal was first identified in 2013 as the cause of mass wild salamander die-offs in the Netherlands and Belgium. Captive salamander die-offs due to Bsal have occurred in the United Kingdom and Germany. Scientists believe Bsal originated in Asia and spread to wild European populations through the import and export of salamanders.

The USGS brought together scientists and managers from federal and state agencies that oversee resource conservation and management to identify research needs and management responses before Bsal arrives and becomes entrenched in the country. USGS, the USFWS, U.S. Forest Service, U.S. Department of Defense, National Park Service, zoos, and U.S. and international universities participated in the Bsal workshop.

Key findings in the report include:

  • Bsal is highly likely to emerge in U.S. populations of wild salamanders through imports of potentially infected salamanders.
  • Management actions targeted at Bsal containment after arrival in the United States may be relatively ineffective in reducing its spread.
  • A coordinated response, including rapid information sharing, is necessary to plan and respond to this potential crisis.
  • Early detection of Bsal at key amphibian import locations, in high-risk wild populations, and in field-collected samples is necessary to quickly and effectively implement management responses.

“The increasing pace of global commerce and emergence of new infectious diseases put vulnerable native wildlife populations at risk for extinction,” said Grant. “Managing disease threats to the 191 species of U.S. salamanders is essential for the global conservation of salamanders.”

Grant noted that the process by which Bsal research and management needs were identified could be adapted for future infectious disease threats to wildlife.

The workshop and Open-File Report were supported by the USGS Amphibian Monitoring and Research Initiative — or ARMI — and the USGS Powell Center for Analysis and Synthesis. ARMI is a national program focusing on amphibian research to stop or reverse the worldwide decline in amphibian populations from habitat change to disease.  Science Daily  Original web page at Science Daily


Save the salamanders

Batrachochytrium salamandrivorans (Bsal) is an emerging fungal pathogen that has caused recent die-offs of salamanders in Europe. Laboratory experiments have shown that it can kill some North American species as well, confirming a serious threat to salamander populations on the continent.

A Pearl (a short essay) published on December 10th in PLOS Pathogens summarizes what is known about the threat posed by the pathogen, discusses current initiatives in the USA, Canada, and Mexico to mitigate the threat, and calls for the creation of a North American Bsal Strategic Plan.

“All evidence suggests that we are at a critical time of action to protect global amphibian biodiversity by swift policy actions to prevent the translocation of Bsal,” state corresponding author Matthew Gray from the University of Tennessee in Knoxville, USA, and colleagues from the USA, Mexico, Canada, and Europe.

As they discuss, North America is a global hotspot for salamander biodiversity, accounting for about 50% of species worldwide. In the continent’s forests, the biomass of salamanders can exceed the biomass of all other vertebrate species, and salamanders are key players in a variety of ecosystems.

The lesson from other recently introduced fungal plant and animal pathogens (including those causing white-nose syndrome in bats or chestnut blight), they say, is that “preventing introduction is the best way to protect populations, but, if introduction occurs, rapid response is essential.”

Bsal was likely introduced to Europe from Asia through the commercial amphibian trade. Salamanders represent 5.5% of the amphibians imported into the USA, and their estimated annual market value is less than a million US dollars.

The authors mention that one European country has responded to the Bsal threat with a total import ban for salamanders. They do not call for such a ban in North America, but the proposed plan includes “strategies to prevent or reduce the risk of Bsal entry into the United States, Canada, and Mexico.”

Overall, they state that “the response to the threat of Bsal behooves a cooperative effort across non-governmental organizations, government agencies, academic institutions, zoos, the pet industry, and concerned citizens to avoid the potential catastrophic effects of Bsal on North American salamanders” and propose concrete steps to be taken immediately.  Science Daily  Original web page at Science Daily


Land use may weaken amphibians’ capacity to fight infection, disease

Human-made changes to the environment may be damaging the immune systems of a species of frog whose populations have drastically declined since the 1970s, according to a new study by researchers at Case Western Reserve University and the Holden Arboretum.

“These Blanchard’s cricket frogs have nearly gone extinct in their northern range, so we’re almost forensically trying to understand what happened,” said Mike Benard, a biology professor at Case Western Reserve. “This study suggests that changes we are making to the environment have the potential to make animals more susceptible to diseases and therefore may lead to population declines.”

Scientists found that habitat characteristics explained the differences in immune defense traits of frogs between populations. They found that the skin microbiomes ?symbiotic bacterial and fungal communities on the skin ?of frogs from disturbed sites, like residential and agricultural lands, were different from the skin microbiomes of frogs from more natural habitats. They also found natural peptide secretions–proteins frogs secrete from their skin that protect against pathogens–differed between frogs from different environments. Both changes potentially alter the amphibian’s immune defense capabilities. These findings and more are published in the journal Biological Conservation.

Research is increasingly showing that microbiomes in the gut and on the skin and antimicrobial peptides excreted by humans and other animals play important roles in fighting infection and disease.

“We’re seeing a lot of disease-related declines among amphibians, not to mention other groups of animals, such as bats plagued with white-nose syndrome and bees suffering from colony collapse disorder,” said Katherine Krynak, a postdoctoral scholar in Case Western Reserve’s Department of Biology and leader of the study. “This research shows that land use–farming or treating lawns with herbicides, pesticides and fertilizers–can influence traits that protect animals from disease.”

Blanchard’s cricket frogs are about an inch long. They had once been widely spread across Wisconsin, Michigan and northern Ohio, but now only pockets remain in this northern region.

Frogs used in the study were from ponds in various habitats: natural ponds surrounded by forest or prairie, or more disturbed ponds surrounded by houses, on farmed land or near athletic fields, parking lots and golf courses. In addition to considering the physical differences, the researchers tested water chemistry and quality in each pond.

With permission from the states of Ohio and Michigan, Krynak, Benard and David Burke, a scientist and research chair at Holden Arboretum in Kirtland, Ohio, examined samples Krynak had collected from the frogs. Krynak used Q-tip like swabs to obtain samples of the skin microbiome, and then placed the frogs in a solution that gently induced the animals to secrete the antimicrobial peptides.

Krynak and Burke then used molecular methods to examine the community of microbes on the frogs’ skin. Burke, who studies symbiotic interactions between plants and microbial communities, is also an adjunct assistant professor of biology at Case Western Reserve. Krynak and Burke also examined the amount of peptides the frogs produced and how effective the peptides were against an amphibian pathogen they cultured in the lab.

The researchers found microbiome differences between frogs that live in natural areas, such as a pond owned by the Nature Conservancy, and those in ponds surrounded by highly “managed” land, such as farmland or residential properties.

“What we’re seeing is the bacteria on the skin can vary markedly, depending on what people are doing to the environment that the frogs are living in,” Burke said.

A pond’s latitude, conductivity–a proxy for chemical runoff–and size also appear to affect the microbiome.

The amount of natural peptide secretions produced from the frogs’ skin also varied across sites and was influenced by both the size of the pond and the conductivity of the water. Some of the skin secretions have been shown to fight off fungal infections, Krynak said. But in petri dishes in the lab, the growth rate of chytrid fungus, which has been linked to devastating population declines in amphibians worldwide, climbed with increasing Blanchard’s cricket frog natural peptide secretions.

The researchers will further investigate why higher concentrations of peptides appear to allow the killer fungus to grow faster in this species.

“This pattern suggests that in areas where land use increases the amount of the peptides these frogs produce, this particular pathogen could have devastating effects” Krynak said.

The team will also look more directly at how the environment interacts with a population’s genes, changing the expression of traits. “Not only may the environment be altering traits now, but it may be dampening the ability of a population to adapt in the future,” Krynak said.

They are also experimentally isolating factors such as how a commonly used and commercially available glyphosate-based herbicide may alter these immune defense traits.

Environmental alteration of defense traits may explain why different amphibian populations show different levels of resistance to infection and disease.

Krynak said there’s a strong chance that the environment is affecting these traits in other amphibians and wildlife in general.”By improving our understanding of the factors influencing immune defense traits capabilities, we are given the opportunity to make changes to our land management practices to better protect wildlife health” she said “and in all likelihood, our own health as a consequence.”  Science Daily  Original web page at Science Daily


Wild toads saved from killer fungal disease

After a six-year effort, biologists say they have for the first time managed to rid a wild toad species of a lethal fungal disease that threatens amphibians around the world.

Midwife toads on the Spanish island of Mallorca are now free of the chytrid fungus Batrachochytrium dendrobatidis, says Jaime Bosch, an evolutionary biologist at Spain’s National Museum of Natural History in Madrid. His team reported their success in the journal Biology Letters on 18 November. But the successful treatment — which involved treating tadpoles with an antifungal drug and chemically cleansing their ponds — may not be widely applicable to the habitats of other amphibian species that are threatened by chytrid, the researchers and others say.

The fungal disease is one of the greatest threats amphibians face across the globe: chytrid has already wiped out hundreds of species of frogs. Bosch and his colleagues in Spain and the United Kingdom first set out to save isolated populations of vulnerable midwife toads on Mallorca in 2009. The fungus was spreading on the toads’ skin, stifling their ability to breathe and manage their water balance, and ultimately killing them.

The researchers removed all the toads’ tadpoles and treated them in the laboratory with the antifungal drug itraconazole, while also draining and drying out their ponds in the hope of eliminating the pathogen. But after they were returned home – via helicopter – the first batch of successfully treated tadpoles was soon infected with the fungus again.

In 2012, the researchers tried again: this time, they drained and treated one set of ponds with Virkon S, an agricultural disinfectant made by DuPont. Tadpoles that were returned to those ponds a year later remained healthy, whereas those returned to ponds that were drained but not treated fell ill. After disinfecting the rest of the ponds, the researchers found no evidence of fungal infection two years on.

It is still unclear exactly where and how the fungus lingered in the untreated drained ponds, though Bosch and his team suspect that tadpoles were being reinfected by adult toads that remained tucked out of sight. The team sprayed disinfectant into nooks and crannies, so may have managed to reach the hidden adults.

“It’s pretty exciting that they were able to eliminate chytrid fungus in multiple sites across the island,” says Karen Lips, a conservation biologist at the University of Maryland, College Park. But Lips thinks that the treatment may only work in specific habitats. Mallorca is dry, with granite-carved ponds that flood seasonally, and few other species live there that could reintroduce the fungus. “Not many other places are geared to this approach,” Lips says. Exceptions include other isolated environments such as captive breeding programmes, zoos, laboratories and other kinds of islands — for example, urban islands and mountaintops. Still, she says, in places where species are endangered and costs are not a barrier, “I think this shows there are certain things you can do.”

To rid many amphibians of their fungal infection, it will be necessary to find another way, Bosch agrees. But the study shows that it may be worth trying the aggressive chemical intervention in some circumstances, he says. One of Bosch’s co-authors, Trent Garner of the Zoological Society of London, would like to see more mitigation efforts. “We spray for fungal infections in our crops every year,” he says. “Are there other things that we could use that could be applied environmentally and at a large scale?”

Doug Woodhams, an amphibian disease ecologist at the University of Massachusetts, Boston, hopes that interventions that don’t involve extensive spraying of antifungal chemicals might also work. In his laboratory he is trying probiotic therapy, which introduces beneficial microbes to fight fungal infection — but he has yet to prove that it works in the wild.

Meanwhile, in southeast continental Spain, which has a similar geographical landscape to Mallorca, Bosch and his colleagues are using their method to try to protect populations of the Betic midwife toad. Endemic to the region for millions of years, the toads now inhabit a landscape where humans have shifted water into artificial ponds meant for cattle. The toads now make these plastic-lined pools their home — a perfect setting in which to knock out the chytrid fungus.

Artificial cattle ponds in southeast Spain, where fungal-infected Betic midwife toads now reside, will also be cleansed.

Nature doi:10.1038/nature.2015.18814  Nature  Original web page at Nature


Estrogen, shrubbery, and the sex ratio of suburban frogs

A new Yale study shows that estrogen in suburban yards is changing the ratio of male and female green frogs at nearby ponds. Higher levels of estrogen in areas where there are shrubs, vegetable gardens, and manicured lawns are disrupting frogs’ endocrine systems, according to the study. That, in turn, is driving up the number of female frogs and lowering the number of male frogs.

The research appears in the journal Proceedings of the National Academy of Sciences. It is based on tests conducted at 21 ponds in southwestern Connecticut in 2012. Previous studies have shown similar effects caused by agricultural pesticides and wastewater effluent; the new study finds amphibian endocrine disruption also exists in suburban locales.

“In suburban ponds, the proportion of females born was almost twice that of frog populations in forested ponds,” said lead author Max Lambert, a doctoral student at the Yale School of Forestry & Environmental Studies. “The fact that we saw such clear evidence was astonishing.”

The researchers looked at ponds with varying degrees of suburban neighborhood impact — with entirely forested ponds at one end of the spectrum, and ponds that were heavily surrounded by suburbia at the other end. The sites included ponds linked to both septic systems and sewer lines. In many cases, the researchers needed to obtain permission from homeowners to survey their back yards.

“Our work shows that, for a frog, the suburbs are very similar to farms and sewage treatment plants,” Lambert said. “Our study didn’t look at the possible causes of this, partly because the potential relationship between lawns or ornamental plantings and endocrine disruption was unexpected.” Lambert noted that some plants commonly found in lawns, such as clovers, naturally produce phytoestrogens. The simple act of maintaining a lawn, in other words, may be one source of the contamination.

There also are possible implications for other species that use suburban ponds, note the researchers. Those species include other amphibians, such as wood frogs, spring peepers, gray tree frogs, and salamanders, as well as birds, turtles, and mammals. “Some of our lab’s current work is trying to understand how the suburbs influence sexual development in other species,” Lambert said.  Science Daily  Original web page at Science Daily


Vestibular organ: Signal replicas make a flexible sensor

When a jogger sets out on her or his evening run, the active movements of the arms and legs are accompanied by involuntary changes in the position of the head relative to the rest of the body. Yet the jogger does not experience feelings of dizziness like those induced in the passive riders of a rollercoaster, who have no control over the abrupt dips and swoops to which they are exposed. The reason for the difference lies in the vestibular organ (VO) located in the inner ear, which controls balance and posture. The VO senses ongoing self-motion and ensures that, while running, the jogger unconsciously compensates for the accompanying changes in the orientation of the head. The capacity to adapt and respond appropriately to both slight and substantial displacements of the head in turn implies that the sensory hair cells in the inner ear can react to widely varying stimulus intensities.

In collaboration with Dr. John Simmers at the Centre national de la recherche scientifique (CNRS) at the University of Bordeaux, neurobiologists Dr. Boris Chagnaud, Roberto Banchi and Professor Hans Straka at LMU’s Department of Biology II, have now shown, for the first time, how this feat is achieved. Their findings reveal that cells in the spinal cord which generate the rhythmic patterns of neural and muscle activity required for locomotion also adaptively alter the sensitivity of the hair cells in the VO, enabling them to respond appropriately to the broad range of incoming signal amplitudes. The results are reported in the online journal Nature Communications. As Boris Chagnaud points out, “we are not really aware of what movement actually involves because our balance organs react immediately to alterations in posture and head position. The hair cells, which detect the resulting changes in fluid flow in the semicircular canals in the inner ear, enable us to keep our balance without any conscious effort.”

Using tadpoles as an experimental model system, the researchers investigated how the hair cells manage to sense both low- and high-amplitude movements and produce the signals that control the appropriate compensatory response. The tadpole’s balance organs operate on the same principle as the bilateral VOs in humans, and the nerve circuits responsible for communication between the hair cells and the motor neurons in the spinal cord are organized in essentially identical ways.

When a tadpole initiates a voluntary movement, e.g., begins to swim by moving its tail from side to side, nerve cells in the spinal cord send copies of the motor commands to so-called efferent neurons in the brainstem that project to the hair cells in the inner ear. “The effect of this signal is to reduce the sensitivity of the hair cells,” says Chagnaud. By dampening the intrinsic sensitivity of the hair cells, the input from the spinal cord effectively adapts the VO’s dynamic range. This process enables the balance organ to maintain responsiveness to high-amplitude “afferent” stimuli from the periphery, and thus to modulate the head movements that accompany propulsive swimming.

Hence the whole adaptation process is controlled by neurons in the spinal cord, which transmit signals to the VO via nerve cells located in the brainstem just before the muscles carry out the next locomotory behavior. These signals thus notify the VO in advance about the temporal form of the impending movement. “This feedforward principle is crucial, because it prepares the hair cells to react appropriately to the next movement,” Chagnaud explains. “The direct impact of input from the spinal cord on the sensitivity of sensory nerve cells in the balance organ demonstrates the importance of interactions between sensory and motor systems, and it underlines the significance of the interplay between different components of the central nervous system — in this case, the spinal cord and the brainstem. Here, evolution has not only come up with an elegant means of anticipating the effects of locomotion on the body but also of compensating for them in an adaptive fashion.”

The LMU group now intends to study whether all the hair cells in the inner ear also respond to efferent information emanating from the spinal cord or whether the VO possess subpopulations of hair cells that are specialized for reception of impulses that signal either fast or slow movements.  Science Daily  Original web page at Science Daily


Climate change could leave Pacific Northwest amphibians high and dry

Far above the wildfires raging in Washington’s forests, a less noticeable consequence of this dry year is taking place in mountain ponds. The minimal snowpack and long summer drought that have left the Pacific Northwest lowlands parched also affect the region’s amphibians due to loss of mountain pond habitat. According to a new paper published Sept. 2 in the open-access journal PLOS ONE, this summer’s severe conditions may be the new normal within just a few decades.

“This year is an analog for the 2070s in terms of the conditions of the ponds in response to climate,” said Se-Yeun Lee, research scientist at University of Washington’s Climate Impacts Group and one of the lead authors of the study. We’ve seen that the lack of winter snowpack and high summer temperatures have resulted in massive breeding failures and the death of some adult frogs,” said co-author Wendy Palen, an associate professor at Canada’s Simon Fraser University who has for many years studied mountain amphibians in the Pacific Northwest. “More years like 2015 do not bode well for the frogs.”

Mountain ponds are oases in the otherwise harsh alpine environment. Brilliant green patches amid the rocks and heather, the ponds are breeding grounds for Cascades frogs, toads, newts and several other salamanders, and watering holes for species ranging from shrews to mountain lions. They are also the cafeterias of the alpine for birds, snakes and mammals that feed on the invertebrates and amphibians that breed in high-altitude ponds.

The authors developed a new model that forecasts changes to four different types of these ecosystems: ephemeral, intermediate, perennial and permanent wetlands. Results showed that climate-induced reductions in snowpack, increased evaporation rates, longer summer droughts and other factors will likely lead to the loss or rapid drying of many of these small but ecologically important wetlands.

According to the study, more than half of the intermediate wetlands are projected to convert to fast-drying ephemeral wetlands by the year 2080. These most vulnerable ponds are the same ones that now provide the best habitat for frogs and salamanders.

At risk are unique species such as the Cascades frog, which is currently being evaluated for listing under the Endangered Species Act. Found only at high elevations in Washington, Oregon and California, Cascades frogs can live for more than 20 years and can survive under tens of feet of snow. During the mating season, just after ponds thaw, the males make chuckling sounds to attract females.

“They are the natural jesters of the alpine, incredibly tough but incredibly funny and charismatic,” said Maureen Ryan, the other lead author, a former UW postdoctoral researcher who is now a senior scientist with Conservation Science Partners.

The team adapted methods developed for forecasting the effects of climate change on mountain streams. Wetlands usually receive little attention since they are smaller and often out of sight. Yet despite their hidden nature, ponds and wetlands are globally important ecosystems that help store water and carbon, filter pollution, convert nutrients and provide food and habitat to a huge range of migratory and resident species. Their sheer numbers — in the tens of thousands across the Pacific Northwest mountain ranges — make them ecologically significant.

“It’s hard to truly quantify the effects of losing these ponds because they provide so many services and resources to so many species, including us,” Ryan said. “Many people have predicted that they are especially vulnerable to climate change. Our study shows that these concerns are warranted.

Land managers can use the study’s maps to prepare for climate change. For example, Ryan and co-authors are working with North Cascades National Park, where park biologists are using the wetland projections to evaluate and update priorities for managing introduced fish and restoring natural alpine lake habitat.  Science Daily  Original web page at Science Daily


Newly identified tadpole disease found across the globe

Scientists have found that a newly identified and highly infectious tadpole disease is found in a diverse range of frog populations across the world. The discovery sheds new light on some of the threats facing fragile frog populations, which are in decline worldwide.

The study, published in the Proceedings of the National Academy of Sciences journal, led by the University of Exeter and the Natural History Museum, describes the molecular methods used to test frog tadpoles for a newly identified infectious agent.

Tadpoles from six countries across three continents were tested for ‘protists’ — single celled microbes with complex cells which store their DNA in a nucleus, like human cells. The previously unidentified parasite was present in tadpole livers in both tropical and temperate sites, and across all continents tested. The infectious agent was identified as a distant relative of Perkinsea sp., a marine parasites found in animals and algae.

Professor Thomas Richards from the University of Exeter said: “Global frog populations are suffering serious declines and infectious disease has been shown to be a significant factor. Our work has revealed a previously unidentified microbial group that infects tadpole livers in frog populations across the globe.”

“We now need to figure out if this novel microbe — a distant relative of oyster parasites — causes significant disease and could be contributing to the frog population declines.”

It is widely recognised that amphibians are among the most threatened animal groups: for example, in 2008, 32% of species were listed as ‘threatened or extinct’ and 42% were listed as in decline. The decline of amphibian populations, particularly frogs, is thought to suggest that Earth is currently undergoing a sixth mass extinction event. Science Daily  Original web page at Science Daily


Frogs mount speedy defence against pesticide threat

Several species of frogs can quickly switch on genetic resistance to a group of commonly used pesticides. In one case, wood frogs (Lithobates sylvaticus) were able to deploy such defences in just one generation after exposure to contaminated environments, scientists reported last week at a conference of the Ecological Society of America in Baltimore, Maryland.

This is the first-known example of a vertebrate species developing pesticide resistance through a process called phenotypic plasticity, in which the expression of some genes changes in response to environmental pressure. It does not involve changes to the genes themselves, which often take many generations to evolve.

The frogs’ speedy response raises hope for amphibian species, of which one-third are threatened or extinct, says Rick Relyea, an ecologist at the Rensselaer Polytechnic Institute in Troy, New York, and the team’s leader.

“Frogs can evolve much faster than we thought,” says Andrew Blaustein, an amphibian ecologist at Oregon State University in Corvallis. “It is possible these stunning findings could have some practical value for conservation but the situation is complex. There is a cocktail of problems.”

In 2013, Relyea and his team discovered that L. sylvaticus frogs living near agricultural land in northwest Pennsylvania were resistant to the pesticide carbaryl. Laboratory tests revealed that frog embryos and hatchlings living far from farmers’ fields were not pesticide-resistant but could quickly become tolerant when exposed to low levels of the pesticide.

Subsequent research revealed that another species, the grey tree frog (Hyla versicolor), can also switch on resistance to carbaryl in the same speedy way as L.sylvaticus3. And frogs that develop resistance to carbaryl also show resistance to another pesticide, malathion4. Both pesticides work by inhibiting the enzyme Acetylcholine esterase (AChE), which acts on a neurotransmitter.

“If inducible tolerance occurs more widely in nature, it would alter our perspective on how pesticides affect organisms,” says Relyea.

Some of the team’s latest published research shows that L. sylvaticus individuals living close to contaminated farmland evolve to permanently express the resistance after natural selection favours the “switched-on” phenotype, in a process known as genetic assimilation. In contrast, populations inhabiting pesticide-free land show their tolerance only after exposure to low levels of the chemicals.

Scientists have observed only a few other species evolving as a result of phenotypic plasticity, such as plants shifting to live at higher altitudes in response to climate change.

Relyea suggests that agricultural pests such as mites and beetles — the intended targets of pesticides — could also develop resistance in the same way. Understanding how tolerance evolves could help farmers to prevent pests from developing resistance. Farmers might not apply an initial round of pesticide at low doses if they knew it could help pests to become resistant, he adds.

Nature doi:10.1038/nature.2015.18197 Nature  Original web page at Nature


Urgent action needed to protect salamanders from deadly fungus, scientists warn

A deadly fungus identified in 2013 could devastate native salamander populations in North America unless U.S. officials make an immediate effort to halt salamander importation, according to an urgent new report published today in the journal Science.

San Francisco State University biologist Vance Vredenburg, his graduate student Tiffany Yap and their colleagues at the University of California, Berkeley and the University of California, Los Angeles say the southeastern United States (particularly the southern extent of the Appalachian Mountain range and its southern neighboring region), the Pacific Northwest and the Sierra Nevada, and the central highlands of Mexico are at the highest risk for salamander declines and extinctions if the fatal Batrachochytrium salamandrivorans (Bsal) fungus makes its way into those regions.

Salamanders are popular worldwide as pets, and frequently traded across borders. That has scientists worried that the fungus could spread from Asia, where it likely originated, to other parts of the globe. Vredenburg and his coauthors on the study are asking the U.S. Fish and Wildlife Service to place an immediate ban on live salamander imports to the U.S. until there is a plan in place to detect and prevent the spread of Bsal. Although the ban has been supported by key scientists for some time, including in a prominent op-ed in the New York Times last year, the government has been slow to act.

“This is an imminent threat, and a place where policy could have a very positive effect,” Vredenburg said. “We actually have a decent chance of preventing a major catastrophe.”

Salamanders are one of the most abundant vertebrate animals in many North American ecosystems and play a number of key ecological roles. “They are very important predators of insects, but also an important part of the food chain,” noted Vredenburg, an associate professor of biology.

Bsal likely originated in Asian species of salamander that are traded as popular pets around the world. When the fungus made its way into Europe through the pet trade, it caused a 96 percent fatality rate among the European salamander species that it infected. It was also fatal to American salamanders exposed to the fungus in the lab.

The blue-tailed fire-bellied newt (Cynops cyanurus), the Japanese fire-bellied newt (Cynops pyrrhogaster), and the Tam Dao or Vietnamese salamander (Paramesotriton deloustali) are thought to be the main carriers of Bsal. Alarmingly, 91 percent of pet salamanders imported to North America come from either the Cynops or Paramesotriton groups.

“We’ve made specific predictions, on the ground, of where North American species are most vulnerable to Bsal,” said Vredenburg. “And the places that have the highest amount of trade in these salamanders happen to be in those high-risk areas.

To map out high-risk regions of Bsal infection in North America, the research team looked at habitats where the fungus might thrive, based on its Asian carrier locations, along with data on how many different species might be threatened in those areas and the location of major U.S. ports of entry for salamander trade between 2010 and 2014

Vredenburg fears that the salamanders might be on the verge of an ecological crisis that is all too familiar to him. For more than a decade he has studied the impact of a similarly deadly fungus called Batrachochytrium dendrobatidis (Bd). More than 200 species of amphibians have gone extinct or are near to extinction as a result of Bd infection, making it the most devastating infectious wildlife disease ever recorded.

“I have seen the effects of Bd on frogs, to the point where I’ve seen tens of thousands of animals die in the wild in pristine areas, here in California, right in front of my eyes,” Vredenburg said. “It is just an unbelievable sight to see all these dead animals.”

The heartbreaking work might have a silver lining, he said, if it can be used to save the salamanders from a similar plight.

“One of the things that I find remarkable about this is that unlike when we first figured out what was going on with Bd, no one could even imagine that one pathogen could cause so much damage across all these different species, because we had never seen anything like that ever before,” Vredenburg said. “What’s encouraging about this time, with Bsal, is that the scientific community figured it out really quickly, and we can learn a lesson from the past.”

Vredenburg is the co-founder of AmphibiaWeb, an online database of information on amphibian biology that receives 7.3 million queries each year. Salamanders are astonishing animals, he said, ranging from species that live 35 feet up in the trees to others that roll into balls and hurl themselves off cliffs to escape predators. The familiar California slender salamanders, found all over Northern California, are one of the groups most threatened by Bsal infection.

“They’re incredibly diverse, they’ve been around for tens of millions of years, and the thought of losing them because of human error, humans moving pathogens around by accident, is just a terrible thought,” Vredenburg said. “And it’s preventable.”  Science Daily  Original web page at Science Daily


Animals can adapt to increasingly frequent cold snaps

As worldwide temperatures rise and the earth sees extreme weather conditions in both summer and winter, a team of researchers with the University of Florida and Kansas State University have found that that there is potential for insects – and possibly other animals – to acclimate and rapidly evolve in the face of this current climate change.  “Organisms can deal with these stressful transitions from warm to cold by either acclimating – think about dogs putting on their winter coats – or by populations genetically evolving to deal with new stresses, a phenomenon known as rapid climate adaptation,” said Alison Gerken, a post-doctoral associate with UF’s Department of Molecular Genetics and Microbiology and the lead author of a new study, published this month in the journal Proceedings of the National Academy of Sciences.

While much of the emphasis regarding climate change is on overall warming, increased frequency of extreme weather events is also a critical concern. As fall and spring temperatures rise, animals will increasingly have to deal with rapid changes from warm conditions to dangerously cold temperatures as weather fronts sweep through. These “snap freeze” events threaten a variety of plants from agricultural crops to landscaping that are damaged and animals like insects, frogs, and even sea turtles that can suffer from cold. Using fruit flies, Gerken and her team have described the genetic architecture for both long-term acclimation, as would be needed to prepare for the transition from summer to winter, and short-term acclimation, which could occur over a single day with a snap freeze. They have shown that there is substantial genetic variation in nature for both long-term seasonal acclimation and short-term acclimation associated with rapid extreme weather events.

“The ability to respond to longer-term seasonal changes does not impede the ability to respond to rapid changes associated with short-term extreme cold events,” said Daniel Hahn, associate professor of insect physiology with UF’s Institute of Food and Agricultural Sciences’ Department of Entomology and Nematology. “We have identified a series of about 100 candidate genes that could explain the ability of animals to rapidly respond to fluctuating temperatures.” “Identifying which of these candidate genes actually causes variation in responses to cold snaps will give us the potential to understand whether evolution to climate change can occur in both wild and domesticated animals, allowing us to better predict which species or breeds will be “winners” and “losers” and to better mitigate the effects of anthropogenic climate change on a wide range of organisms from beneficial pollinators to invasive pests,” said Theodore Morgan an associate professor of evolutionary genetics in the Division of Biology at Kansas State University and senior author of the study. Gerken, Hahn, and Morgan say identifying the genes involved in acclimation to temperature and the genetic relationship between long-term and short-term acclimation provides us with new tools to predict the impacts of an increased frequency of extreme events as a by-product of anthropogenic climate change on animal and plant populations.  Science Daily Original web page at Science Daily


Frog uses different strategies to escape ground, air predators

Frogs may flee from a ground predator and move towards an aerial predator, undercutting the flight path, according to a study using model predators published April 15, 2015 in the open-access journal PLOS ONE by Matthew Bulbert from Macquarie University, Australia and colleagues. Escape from a predator is often the last line of defense for an organism. The authors of this study evaluated the effectiveness of different escape strategies of the ground-dwelling túngara frog from two types of predators, one approaching from the air and one from the ground. Researchers selected two disparate predators known to prey on calling túngara frogs. The aerial predator, modeled after a fringed-lipped bat, was deployed using a zip-line, which passed directly over the frog. The ground predator, a rubber snake modeled after a cat-eye snake, was pulled toward the calling frog along the ground. Both model predators were only deployed while males were actively calling.

Túngara frogs showed consistently distinct escape responses when attacked by ground versus aerial predators. The frogs fled away from the snake models. In stark contrast, the frogs moved toward the bat models, effectively undercutting the bat’s flight path. The authors results reveal that prey escape direction reflect the type of predators’ attacks. The authors suggest that this study emphasizes the flexibility of strategies used by prey to escape predators with diverse modes of attack.  Science Daily Original web page at Science Daily


* Deadly frog fungus dates back to 1880s, studies find

A pair of studies show that the deadly fungus Batrachochytrium dendrobatidis, responsible for the extinction of more than 200 amphibian species worldwide, has coexisted harmlessly with animals in Illinois and Korea for more than a century. The research will help biologists better understand the disease caused by Bd, chytridiomycosis, and the conditions under which it can be survived. Amphibians in Illinois have been coexisting with the fungus Batrachochytrium dendrobatidis, or Bd, for at least 126 years without adverse effects seen in other parts of the world such as mass-die offs, according to research published Jan. 13 in the journal Biological Conservation. In a study published March 4 in PLOS ONE, researchers were able to date the fungus in Korea back to 1911. The results will help scientists better understand the disease caused by Bd, chytridiomycosis, and the conditions under which it can be survived. “Part of understanding a disease is understanding the dynamics of the host and pathogen,” said Vance Vredenburg, an associate professor of biology at San Francisco State University and co-author of the studies, who has been researching Bd for more than a decade. “What we have now is a benchmark where the dynamics have been stable for well over 100 years.”

Before the new study, the earliest confirmed instance of Bd was in Brazil during the 1890s. The discovery in Illinois also dates back 50 years earlier than previous instances for North America. Chytridiomycosis, or chytrid, has driven more than 200 amphibian species worldwide to extinction and poses the greatest threat to vertebrate biodiversity of any known disease. Vredenburg has tracked the spread of the disease since 2003 in such places as the Sierra Nevada and Andes mountains, including identifying such common carriers as the African clawed frog, the American bullfrog and Pacific chorus frog. Human transportation of these animals is one way to explain how Bd — and the resulting disease chytridiomycosis — is introduced to new populations, sparking mass die-offs.

“This fungus has been emerging all over the world and causing major, major problems,” Vredenburg said. “Taking the information we now have from this research, we can look at the animals in Illinois and Korea, figure out how they are surviving and translate that knowledge to other parts of the world where we see massive declines of amphibian populations.” One key difference in the two studies is that, while testing showed that Bd was widespread in Illinois dating back to the 1880s, the disease was far less common in Korea during the 1900s than it is today. That, Vredenburg said, indicates that the behavior of the fungus differs depending on location, a key piece of information for biologists to keep in mind when studying its spread.

The study also validates the effectiveness of testing for Bd in museum specimens, which a graduate student, Tina Cheng, pioneered at SF State. Some of the museum specimens are more than 100 years old, prompting concerns that older DNA may have degraded, leading to “false negatives,” but Vredenburg and his colleagues found the fungus on some of the oldest samples available. During the two studies, researchers tested more than 1,200 amphibian samples collected between 1888 and 2004. The next step, Vredenburg said, is to pinpoint which attributes allow Illinois-area and Korean amphibians to co-exist with the fungus so that biologists can use that information in their efforts to study this disease in other parts of the globe and prevent further extinctions. Science Daily  Original web page at Science Daily


Amphibian chytrid fungus reaches Madagascar

The chytrid fungus, which is fatal to amphibians, has been detected in Madagascar for the first time. This means that the chytridiomycosis pandemic, which has been largely responsible for the decimation of the salamander, frog and toad populations in the USA, Central America and Australia, has now reached a biodiversity hotspot. The island in the Indian Ocean is home to around 290 species of amphibians that are not found anywhere else in the world. Another 200 frog species that have not yet been classified are also thought to live on the island. Researchers from the Helmholtz Centre for Environmental Research (UFZ) and TU Braunschweig, together with international colleagues, are therefore proposing an emergency plan. This includes monitoring the spread of the pathogenic fungus, building amphibian breeding stations and developing probiotic treatments, say the scientists, writing in Scientific Reports, the acclaimed open-access journal from the publishers of Nature. The entire amphibian class is currently afflicted by a global pandemic that is accelerating extinction at an alarming rate.

Although habitat loss caused by human activity still constitutes the main threat to amphibian populations, habitat protection no longer provides any guarantee of amphibian survival. Infectious diseases are now threatening even seemingly secluded habitats. The most devastating of the known amphibian diseases is chytridiomycosis, which is caused by a deadly chytrid fungus (Batrachochytrium dendrobatidis, or Bd). The fungus attacks the skin, which is particularly important in amphibians because they breathe through it. A large number of species have already been lost in this way — particularly in tropical Central America, where two-thirds of the colourful harlequin frog species have already been decimated across their entire area of distribution. Bd has now been identified in over 500 amphibian species, 200 of which have seen a significant decline in numbers. The pathogen is therefore classified worldwide as one of the greatest threats to biodiversity. Until now, however, a few islands like Madagascar were thought not to have been affected. The last series of tests from 2005 to 2010 found no trace of the pathogenic fungus there. However, an analysis of the latest series of tests shows that the chytrid fungus also poses a threat to amphibians in Madagascar. “This is sad news for amphibian-lovers around the world,” says Dr Dirk Schmeller of the UFZ, who was involved in analysing the samples. “Firstly, it means that an island that is home to a particularly high number of amphibian species is now at risk. Several hundred species live only on this island. And, secondly, if the pathogen has managed to reach such a secluded island, it can and will occur everywhere. “For the study that has just been published, the research team analysed samples from over 4000 amphibians from 50 locations in Madagascar taken since 2005.

Samples from four species of Madagascan frog (Mantidactylus sp.) taken in 2010, and from one Mascarene frog (Ptychadena mascareniensis) taken in 2011 from the remote Makay massif tested positive for the fungus. In samples from 2013 and 2014 the pathogen was found in five different regions. Prof. Miguel Vences from TU Braunschweig says, “The chytrid fungus was found in all four families of the indigenous Madagascan frogs, which means it has the potential to infect diverse species. This is a shock!” The study also shows that the disease affects amphibians at medium to high altitudes, which ties in with observations from other parts of the world, where the effects of the amphibian epidemic have been felt primarily in the mountains. The fact that the fungus has been identified in a very remote part of the island has puzzled the researchers. There is some hope that it may prove to be a previously undiscovered, native strain of the pathogen, which may have existed in the region for some time and have gone undetected because of a lack of samples. In this case, Madagascar’s amphibians may have developed resistance to it. However, further research is needed to confirm this hypothesis before the all-clear can be given. It is also possible that the fungus was brought to the island in crustaceans or the Asian common toad (Duttaphrynus melanostictus), carried in by migratory birds or humans. “Luckily, there have not yet been any dramatic declines in amphibian populations in Madagascar,” Dirk Schmeller reports. “However, the pathogen appears to be more widespread in some places than others. Madagascar may have several strains of the pathogen, maybe even the global, hypervirulent strain.

This shows how important it is to be able to isolate the pathogen and analyse it genetically, which is something we haven’t yet succeeded in doing.” At the same time, the researchers recommend continuing with the monitoring programme across the entire country to observe the spread of the disease. The scientists also suggest setting up extra breeding stations for key species, in addition to the two centres already being built, to act as arks, so that enough amphibians could be bred to recolonise the habitats in a crisis. “We are also hopeful that we may be able to suppress the growth of the Bd pathogen with the help of skin bacteria,” says Miguel Vences. “It might then be possible to use these bacteria as a kind of probiotic skin ointment in the future.” A high diversity of microbial communities in the water could also reduce the potential for infection, according to earlier investigations conducted by UFZ researchers and published in Current Biology. The outbreak of amphibian chytridiomycosis in Madagascar puts an additional seven per cent of the world’s amphibian species at risk, according to figures from the Amphibian Survival Alliance (ASA). “The decline in Madagascan amphibians is not just a concern for herpetologists and frog researchers,” says Dr Franco Andreone from the International Union for Conservation of Nature (IUCN), who is one of the study authors. “It would be a great loss for the entire world.” In the coming months, the scientists therefore plan to work with the government to draw up an emergency plan to prevent this scenario. Science Daily Original web page at Science Daily


Size matters in the battle to adapt to diverse environments, avoid extinction

A new University of Toronto study may force scientists to rethink what is behind the mass extinction of amphibians occurring worldwide in the face of climate change, disease and habitat loss. The old cliché “size matters” is in fact the gist of the findings by graduate student Stephen De Lisle and Professor Locke Rowe of U of T’s Department of Ecology & Evolutionary Biology in a paper published today in Proceedings of the Royal Society B. By examining research on global patterns of amphibian diversification over hundreds of millions of years, De Lisle and Rowe discovered that “sexually dimorphic” species — those in which males and females differ in size, for example — are at lower risk of extinction and better able to adapt to diverse environments. Their work suggests the ability of males and females in sexually dimorphic amphibian species to independently evolve different traits — such as size — helps them survive extinction threats that kill off others, says De Lisle. He says classic ecological theory would not have predicted that about amphibians, a class of vertebrates that includes frogs, toads, salamanders, newts and caecilians. The conventional school of thought believes different-sized sexes of the same species take up more resources and are less able to adapt and diversify than species where ecologically relevant traits like size are basically the same between males and females. “I think if our results bear on mass extinction at all, it suggests we maybe should start looking more closely at the traits of some of the species that are going extinct,” says De Lisle. “Scientists might start thinking in a new way about how other traits, like sex differences in habitat use or diet, might play a role.” While peacock feathers or deer antlers are understood to help males of those species successfully mate, less is understood about amphibians, which are being wiped out so fast many are going extinct before scientists can identify them.

Some estimate between 30 and 40 per cent of the world’s approximately 7,000 species of amphibians are currently in danger of extinction — more than any other animals on earth — and their decline is a critical threat to global biodiversity. Many scientists believe amphibians serve as “canaries in a coal mine,” and declines in their populations indicate other groups of animals and plants will soon be at risk. Amphibians are not only an important part of the food chain and biodiversity. Some have chemicals in their skins that can be developed into medicines to fight diseases such as cancer and perhaps even AIDS. Because their skins are highly permeable and they have a two-staged life cycle that starts in water and then moves to land, amphibians may be more susceptible to temperature changes, water and air pollution than other animals. The new study by De Lisle and Rowe adds another piece to the puzzle about why some species are doing well while others are in decline or disappearing. For example, both the golden toad and the harlequin frog of Costa Rica’s Monteverde Cloud Forest Preserve disappeared completely in the late 1980s despite living in what was considered a pristine habitat. “Our work suggests we still maybe don’t have the best understanding of what traits might be influencing these extinctions, although now we have the understanding that sexual dimorphism is an important trait,” says De Lisle. Science Daily Original web page at Science Daily


* Researchers reveal how hearing evolved

Lungfish and salamanders can hear, despite not having an outer ear or tympanic middle ear. These early terrestrial vertebrates were probably also able to hear 300 million years ago, as shown in a new study by Danish researchers. Lungfish and salamander ears are good models for different stages of ear development in these early terrestrial vertebrates. Two new studies published in the journals Proceedings of the Royal Society B and The Journal of Experimental Biology show that lungfish and salamanders can hear, despite not having an outer ear or tympanic middle ear. The study therefore indicates that the early terrestrial vertebrates were also able to hear prior to developing the tympanic middle ear. The research findings thus provide more knowledge about the development of hearing 250-350 million years ago. The physical properties of air and tissue are very different, which means in theory that up to 99.9% of sound energy is reflected when sound waves reach animals through the air. In humans and many other terrestrial vertebrates, the ear can be divided into three sections: the outer ear, the middle ear and the inner ear. The outer ear catches sound waves and directs them into the auditory canal. In the middle ear, pressure oscillations in the air are transferred via the tympanic membrane (eardrum) and one or three small bones (ossicles) to fluid movements in the inner ear, where the conversion of sound waves to nerve signals takes place. The tympanic middle ear improves the transfer of sound energy from the surroundings to the sensory cells in the inner ear by up to 1,000 times, and is therefore very important for hearing in terrestrial vertebrates. This is reflected in the fact that different configurations are found in the vast majority of present-day terrestrial mammals, birds, reptiles and amphibians. However, available palaeontological data indicate that the tympanic middle ear most likely evolved in the Triassic period, approximately 100 million years after the transition of the vertebrates from an aquatic to a terrestrial habitat during the Early Carboniferous. The vertebrates could therefore have been deaf for the first 100 million years on land. It is obviously not possible to study the hearing of the early terrestrial vertebrates, which became extinct long ago. However, by studying the hearing of present-day vertebrates with a comparable ear structure, it is possible to learn about the hearing of the early terrestrial vertebrates and the development of aerial hearing. A team of Danish researchers from Aarhus University, Aarhus University Hospital and the University of Southern Denmark therefore studied the hearing of lungfish and salamanders, which have an ear structure that is comparable to that of different kinds of early terrestrial vertebrates. They studied the hearing of lungfish and salamanders by measuring auditory nerve signals and neural signals in the brainstem as a function of sound stimulation at different frequencies and at different levels. Surprisingly, the measurements showed that not only the terrestrial adult salamanders, but also the fully aquatic juvenile salamanders — and even the lungfish, which are completely maladapted to aerial hearing — were able to detect airborne sound despite not having a tympanic middle ear. By studying the animals’ sense of vibration, the researchers were able to demonstrate that both lungfish and salamanders detect sound by sensing the vibrations induced by sound waves. The results show that even vertebrates without outer and middle ears are capable of detecting airborne sound. This means that adaptation to aerial hearing following the transition from aquatic to terrestrial lifestyles during the Early Carboniferous was presumably a gradual process, and that the early terrestrial vertebrates without tympanic middle ears were not deaf to airborne sound during the first 100 million years on land. In addition to making us wiser about hearing in general, the results can provide inspiration in the future to developing clinical treatments for hearing loss.  Science Daily  Original web page at Science Daily


Fungus from Asia threatens European salamanders

North American salamanders and newts are safe for now, but epidemic could spread through pet trade. The North American eastern newt (Nothophthalmus viridescens) could be at risk from an imported fungus. In 2010, a fungus started killing massive numbers of fire salamanders in the Netherlands. Biologists have now discovered that the disease comes from Asia — and that for salamanders elsewhere, it is likely a death sentence. When the Dutch fire salamanders (Salamandra salamandra) started dying out, conservationists collected all the healthy-looking ones they could find in the wild. They gathered about 39 animals, and began keeping them in captivity — but those salamanders started dying, too. Tests for one suspected cause, ranavirus, came back negative. So did tests for a fungus called Batrachochytrium dendrobatidis (Bd), which has been devastating amphibian populations around the world, driving some to extinction. But when An Martel, a veterinary surgeon at Ghent University in Belgium, and her team examined the animals with a microscope, they saw telltale strands of fungus woven into the salamanders’ skin. It turned out to be a new killer fungus, a cousin of Bd that the team named Batrachochytrium salamandrivorans. Now, the researchers report in Science that salamander or newt species in Europe and North America are vulnerable to it. “First we were very happy because it is very exciting to detect a novel species of fungus,” says Martel. “But then it was scary.” By 2013, only 4% of the Dutch fire salamander population was still alive. And there are no natural barriers to prevent the Dutch outbreak and two new outbreaks Belgium from spreading to the rest of Europe. To predict the impact of the fungus, Martel’s team exposed 10 species of frog and toad, 24 species of salamander and newt, and 1 species of wormlike caecilian to spores of the fungus. The fungus attacked only salamanders and newts — and of 44 individual European salamanders infected, 41 died. Next, the researchers tested more than 5,000 individual amphibians from around the world for traces of the fungus. They found B. salamandrivorans in animals from Thailand, Vietnam and Japan — but these amphibians did not seem to be ill, suggesting that they have evolved some defences. It is likely that the outbreaks in Europe began with imported Asian salamanders. The team did not detect the fungus in any North American samples. But Jodi Rowley, an amphibian biologist at the Australian Museum Research Institute in Sydney, says that does not mean the fungus is not a threat to those species. “I would be very surprised if it wasn’t already in America, at least within the pet trade, given the volume of trade of pet salamanders,” she says. “There needs to be increased testing of amphibians as they come in through the borders.” Lobbying for this testing is a passion of Karen Lips, a conservation biologist at the University of Maryland in College   Park who has studied Bd since 1997, and is a co-author of the latest study. “Here in the US, we have no way to require any testing or surveillance of wildlife imports that may be bringing pathogens and parasites,” she says, adding that three bills currently in Congress would call for increased surveillance — but that they are “just sitting there” without any action to turn them into law. “We can take all the things we learned from Bd and do a much better job,” says Lips. But her hopes are tempered by experience. She has seen Bd drive dozens of frog species to extinction in the Americas.  “There is a voice in the back of my head that says don’t get your hopes up so high,” she says. “How good are we at keeping things out, even little microbes? We couldn’t even keep out Ebola.” Nature doi:10.1038/nature.2014.16249  Nature  Original web page at Nature


First amphibious ichthyosaur discovered, filling evolutionary gap

Fossil remains show the first amphibious ichthyosaur found in China by a team led by a UC Davis scientist. Its amphibious characteristics include large flippers and flexible wrists, essential for crawling on the ground. The first fossil of an amphibious ichthyosaur has been discovered in China by a team led by researchers at the University of California, Davis. The discovery is the first to link the dolphin-like ichthyosaur to its terrestrial ancestors, filling a gap in the fossil record. The fossil is described in a paper published in advance online Nov. 5 in the journal Nature. The fossil represents a missing stage in the evolution of ichthyosaurs, marine reptiles from the Age of Dinosaurs about 250 million years ago. Until now, there were no fossils marking their transition from land to sea. “But now we have this fossil showing the transition,” said lead author Ryosuke Motani, a professor in the UC Davis Department of Earth and Planetary Sciences. “There’s nothing that prevents it from coming onto land.”

Motani and his colleagues discovered the fossil in China’s AnhuiProvince. About 248 million years old, it is from the Triassic period and measures roughly 1.5 feet long. Unlike ichthyosaurs fully adapted to life at sea, this one had unusually large, flexible flippers that likely allowed for seal-like movement on land. It had flexible wrists, which are essential for crawling on the ground. Most ichthyosaurs have long, beak-like snouts, but the amphibious fossil shows a nose as short as that of land reptiles. Its body also contains thicker bones than previously-described ichthyosaurs. This is in keeping with the idea that most marine reptiles who transitioned from land first became heavier, for example with thicker bones, in order to swim through rough coastal waves before entering the deep sea. The study’s implications go beyond evolutionary theory, Motani said. This animal lived about 4 million years after the worst mass extinction in Earth’s history, 252 million years ago. Scientists have wondered how long it took for animals and plants to recover after such destruction, particularly since the extinction was associated with global warming. “This was analogous to what might happen if the world gets warmer and warmer,” Motani said. “How long did it take before the globe was good enough for predators like this to reappear? In that world, many things became extinct, but it started something new. These reptiles came out during this recovery.”  Science Daily  Original web page at Science Daily


Amphibian communities collapse in wake of viral outbreak

Two closely related viruses that have been introduced to northern Spain in recent years have already led to the collapse of three different species of amphibian — the common midwife toad, the common toad, and the alpine newt — in the protected area of Picos de Europa (literally “Peaks of Europe”) National Park. In all, six amphibian species have suffered from severe disease and mass mortality as a result of the outbreak, and researchers who report their findings in the Cell Press journal Current Biology on October 16 say that the viruses appear to be on the move. Preliminary evidence shows that related ranaviruses are emerging in other parts of Europe, which surely means more bad news for amphibians ahead. “The capacity of these viruses to infect multiple species means that there is the possibility that some host populations may be extirpated due to infection,” says Stephen Price, now of UCL. “Pathogens that can exploit more than one host simultaneously are able to persist even when one host drops to low numbers, and eventually zero, because there is another susceptible host available.” In one instance observed by the researchers, a snake even became sick and died after feeding on an infected amphibian. The viruses in question belong to the family Iridoviridae. They have been known to cause disease in fish and reptiles but have also been noted for their ability to sicken and kill amphibians in the Americas, Europe, Asia, and Australia. The new study is the first to document the deadly infection striking multiple amphibian species at once with such serious impact. Price’s coauthor Amparo Mora-Cabello de Alba, a biologist in the national park, and her colleagues grew alarmed after witnessing the first mass mortality events in 2005. The illness produces systemic hemorrhaging, open sores, and the death of limb tissues. Park staff contacted Jaime Bosch of Madrid’s Museo Nacional de Ciencias Naturales, an expert in frogs and toads, and together the team began careful monitoring of the park’s amphibians.Worryingly, the species declines observed in the park have shown no sign of rebound, and, in some locations, species have been all but lost. “Our work reveals a group of pathogens that seem to have preexisting capacity to infect and evade immunity in multiple diverse and novel hosts, and that are exerting massive impacts on host communities,” the researchers write.  Science Daily Original web page at Science Daily


New poison dart frog species discovered in Donoso, Panama

A bright orange poison dart frog with a unique call was discovered in Donoso, Panama, and described by researchers from the Smithsonian Tropical Research Institute and the Universidad Autónoma de Chiriquí in Panama, and the Universidad de los Andes in Colombia. In the species description published this week in Zootaxa, it was named Andinobates geminisae for Geminis Vargas, “the beloved wife of [coauthor] Marcos Ponce, for her unconditional support of his studies of Panamanian herpetology.” Every new species name is based on a representative specimen. The specimen for this species was collected Feb. 21, 2011, in the headwaters of the Rio Caño, in the district of Donoso, Colón Province, Panama, by Samuel Valdés, who was then the MWH Global Inc. environment office director, and his field assistant, Carlos de la Cruz. Additional specimens were collected between the Rio Coclé del Norte and the Rio Belen by biologists Marcos Ponce and Abel Batista, then a student at the Universidad Autónoma de Chiriquí. The specimens were deposited in the Museo de Vertebrados at the University of Panama, the Museo Herpetólogico de Chiriquí at the Universidad Autónoma de Chiriquí and in the Círculo Herpetólogico de Panamá. “Abel Batista and Marcos Ponce were the first to note the presence of this species,” said Cesar Jaramillo, Smithsonian herpetologist. “They’ve known it was there for several years. However, they were not sure if it was only a variety of another poison dart frog species, Oophaga pumilio, which exhibits tremendous color variation. Based on morphological characteristics of the adult and the tadpole, I thought it might be a new species of Andinobates.” Andrew Crawford, professor at Universidad de Los Andes and former STRI postdoctoral fellow, sequenced the DNA, confirming that this was a new species of Andinobates. Genetic information about this species is available in the Barcode of Life Data System and in GenBank. A recording of the call is available at Because this new frog species appears to be found in only a very small area, habitat loss and collecting for the pet trade are major threats to its existence. The authors recommend the formulation of special conservation plans to guarantee its survival. A. geminisae is included in the captive breeding program of the Panama Amphibian Rescue and Conservation project, a consortium of six zoos and research institutions dedicated to saving amphibians from the chytrid fungal disease, which is decimating amphibians worldwide, and habitat loss. Original web page Science Daily


How amphibians crossed continents: DNA helps piece together 300-million-year journey

There are more than 7,000 known species of amphibians that can be found in nearly every type of ecosystem on six continents. But there have been few attempts to understand exactly when and how frogs, toads, salamanders and caecilians have moved across the planet throughout time. Armed with DNA sequence data, Alex Pyron, an assistant professor of biology at the GeorgeWashingtonUniversity, sought to accurately piece together the 300-million-year storyline of their journey. Dr. Pyron has succeeded in constructing a first-of-its-kind comprehensive diagram of the geographic distribution of amphibians, showing the movement of 3,309 species between 12 global ecoregions. The phylogeny — or diagram of evolutionary relationships — includes about half of all extant amphibian species from every taxonomic group. “There have been smaller-scale studies, but they included only a few major lineages and were very broad,” Dr. Pyron said. “What we needed was a large-scale phylogeny that included as many species as possible. That allows us to track back through time, not only how different species are related, but also how they moved from place to place.” His findings, which appear in the journal Systematic Biology, suggest that, contrary to popular belief, certain groups of amphibians may have swam long distances from one landmass to another within the past few million years. Biologists have long hypothesized the distribution of extant lineages of amphibians has been driven by two major processes: vicariance and dispersal. Vicariance occurs when a population is separated following a large-scale geophysical event. After the fragmentation of supercontinent Pangaea and the subsequent split of the Laurasian and Gondwanan landmasses, certain groups of amphibians were able to “hitch a ride” from one continent to another, Dr. Pyron explained. The researcher’s biogeographic analysis supports this hypothesis, showing that continental movement can explain the majority of patterns in the distribution of extant species of amphibians.

Dr. Pyron also found that dispersal during the Cenozoic Era (66 million years ago to the present), likely across land bridges or short distances across oceans, also contributed to their distribution. Given their ancient origin, it is unsurprising that the history of amphibians is a mixture of both vicariance and dispersal. But the third and final distribution pattern that Dr. Pyron notes in his study was an unexpected finding. Past studies have assumed that long-distance over water dispersal was essentially impossible for amphibians due to salt intolerance. However, when Dr. Pyron began completing his analysis, he noticed a number of cases of distribution that could not be explained by old age. For instance, one group of frogs found in Australia and New Guinea (pelodryadine hylids) that originated around 61 to 52 million years ago is deeply nested within a group of amphibians that exist only in South America. By the time pelodryadines originated, all major continental landmasses occupied their present-day positions, with South America and Australia long separated from Antarctica. They’re 120 million years too late to have walked to Australia,” Dr. Pyron said. So how could this group of South American amphibians be related to frogs on the other side of the world? “You wouldn’t think that frogs would be able to swim all the way there, but that seems like one of the more likely explanations for how you could have such a young group nested within South America and have it somehow get to this other continent,” Dr. Pyron said. In his study, Dr. Pyron points two other instances of long-distance oceanic dispersal. “What you have is this mixture of processes. You have vicariance, which over 300 million years has put certain groups in Africa, some in Australia and others in South America,” Dr. Pyron said. “But even more recently, within the last few million years, you have these chance events of long distance dispersals across the ocean, which can influence distribution patterns.”

Dr. Pyron’s next research question is whether there is any specific quality, such as tolerance to salt water, which allows some groups of amphibians to be better dispersers. He has also begun to conduct a similar analysis with lizards and snakes to see if the same distribution patterns hold up. And as new species are discovered, Dr. Pyron will continue to revise his model. These findings not only provide evidence for the unlikely hypothesis of long-distance oceanic dispersal, but they also provide a model for explaining the distribution of other species and learning about the geographic diversity of different groups. For example, an endangered frog in South America unconnected to any other major lineages would need to be a high conservation priority. “That’s something we can only learn from a biogeographic analysis,” Dr. Pyron said.  Science Daily  Original web page at Science Daily


A cure for the plague of frogs?

One of the worst scourges of frogs and their kin is Batrachochytrium dendrobatidis (Bd), a deadly fungus that infects nearly half of amphibian species, eats away their skin, and causes heart attacks. Now, a study shows that one kind of frog can learn to avoid the widespread fungus and that two species become resistant with repeated exposures. Although preliminary, the findings suggest that there may be a way to help protect more vulnerable amphibians. “If frogs exposed and cured are therefore ‘vaccinated’ against Bd, then this study has big implications for mitigation of Bd outbreaks in the future and restoration of frog populations that are in captive holding now,” writes biologist Kelly Zamudio of Cornell University, who was not involved in the study, in an e-mail. Amphibians suffer from many threats, including pollution and habitat destruction. It isn’t easy to pin an extinction on Bd, but researchers suspect the fungus is behind the mysterious decline of many species. To study how well frogs can resist the fungus, Jason Rohr, an ecologist at the University of South Florida, Tampa, and colleagues set up experiments with two species that are easy to catch in Florida, the oak toad (Bufo quercicus) and the Cuban tree frog (Osteopilus septentrionalis). First, they investigated whether oak toads could learn to avoid the fungus. After setting up a small chamber in their laboratory, they added the fungus to one side. When oak toads were first put into the chamber, they spent equal amount of time on either side. Then, Rohr and his colleagues removed the toads and killed the fungus with moderate heat. When the same toads were placed back into the chamber, they were less likely to spend time on the side with the fungus, suggesting that they can learn to avoid it. Rohr has additional experiments under way to determine how the toads detect the fungus, but he suspects that contact is painful as the fungus attacks. “It can’t feel good to have your skin digested by an enzyme.” Other trials with both species showed that with each exposure to the fungus, the toad’s and frog’s immune systems strengthened their response. The animals roughly doubled the number of immune cells by the fourth time they encountered the fungus. And a greater proportion of the amphibians survived: Although only 20% made it through the first exposure, more than half escaped their fourth bout with the fungus, the team reports in this week’s issue of Nature.

This finding isn’t relevant to oak toads and Cuban tree frogs in the wild, because the weather is hot enough where they live to usually kill the fungus. But it could help explain how some species in colder environments, such as mountain lakes, have managed to survive. An intriguing finding is that exposure to dead Bd can also increase resistance, which raises the prospect of immunizing highly sensitive species. “That is exciting stuff,” says biologist Karen Lips of the University of Maryland, College Park, although she describes the level of protection as moderate. Rohr hopes to try adding large amounts of dead Bd to ponds to test whether it will help the survival of susceptible frogs. Several important questions remain. It’s not clear whether the resistance is permanent, whether tadpoles can become resistant, or whether it occurs in other species and would be strong enough to save them. And Erica Bree Rosenblum of the University of California, Berkeley, points to logistical challenges of trying to use the discovery, such as through widespread treatment of endangered populations. “I tend to be skeptical about whether it will be easy to translate results from lab studies into direct conservation application.”  Science Magazine Science Magazine


Urban frogs use drains as mating megaphones

A tiny tree frog seems to be using city drains to amplify its serenades to attract females. In research published in the Journal of Zoology, researchers found that the Mientien tree frog native to Taiwan congregates in roadside storm drains during the mating season. Audio recordings revealed that the mating songs of the frogs inside the structures were louder and longer than those of their less-streetwise rivals, who gathered in patches of land next to the drains. “This is perhaps the first study to show that an animal preferentially uses human-made structures to potentially enhance the sounds of its vocal communication signals,” says Mark Bee, a biologist at the University of Minnesota, Twin Cities, in St Paul. “These males could be taking advantage of the enhanced acoustics in drainage ditches to outdo their competition. ”Frogs’ ability to amplify their voices is a known phenomenon. In 2002, researchers showed that male Metaphrynella sundana frogs in Borneo use hollow tree cavities in their natural habitats to boost the volume of their calls. In the latest study, a team led by zoologist Yu-Teh Kirk Lin at the National Taiwan University in Taipei studied Kurixalus idiootocus tree frogs in a wooded suburb of Taipei during the mating season, which lasts from February to September. Males of the species exhibit a ritual known as lekking, and form groups, or leks, during the mating season to compete for females with some kind of courtship behaviour — in its case, singing. The team found that the urban tree frogs used open concrete drains along roads as lek sites — drastically different from those in their natural habitats, where they gather at ponds to warble. The researchers randomly established 11 plots of 10 metres long and 0.5 metres wide within the drains, and adjacent 10-metre-wide sections of land outside the gutters for monitoring after dark when the frogs sing their mating songs.

Researchers found more tree frogs gathered in the concrete gutters than in adjacent areas. They found that the frogs selected storm drains for mating calls much more often than they did the other locations — on average, 1.64 male frogs per square metre, or just over 7 per site, were found inside the drains, and only 0.02 males per square metre, or almost 2 per site, outside. Calls emitted from inside the drains were louder and longer than those outside — both important mate-selection criteria for choosy females in many frog species, says Lin. Although impossible to distinguish with the human ear, acoustic analysis software revealed the drain calls to be about 4 decibels louder than those outside. The length of all 13 notes in a frog’s call were also 10% longer when the call was emitted from inside the drains. But the study did not assess whether these males were indeed more romantically successful than their counterparts. The authors say that further studies are needed to confirm that the males hop into drains specifically to amplify mating calls. Bee notes that there may be other reasons, such as avoiding predators, for the frogs to jump into man-made structures. Alternative hypotheses still need to be eliminated, he says.

Nature doi:10.1038/nature.2014.15362  Nature

July 8, 2014  Original web page at Nature


Toxic toads threaten ‘ecological disaster’ for Madagascar

The unique wildlife of Madagascar is facing an invasion of toxic toads that could devastate the island’s native species. Snakes feeding on the toads are especially at risk of poisoning, as are a host of other animals unique to the island — such as lemurs and endemic birds — and the species could cause harm to humans as well. In a letter to Nature,  11 researchers warn that Asian common toads (Duttaphrynus melanostictus) were observed near Toamasina, the African country’s largest seaport, in March. It is suspected that the amphibians arrived from Asia in shipping containers, and are now taking advantage of what the writers describe as “ideal resources and climate” to establish themselves. “Time is short, so we are issuing an urgent call to the conservation community and governments to prevent an ecological disaster,” say Jonathan Kolby, a wildlife-health researcher at James Cook University in Townsville, Australia, and his colleagues. The discovery of the invasive amphibians recalls the Australian plague of cane toads (Rhinella marina). These animals, relatives of the Asian common toad, were deliberately introduced to Australia in 1935; they proceeded to devastate native animal populations and have spread across much of the country, defying attempts to eradicate them. Kolby and his colleagues warn that something similar could now happen in Madagascar. The toads are already reported to have been deadly to snakes, including the ground boa (Acrantophis spp.), which is found nowhere else, Kolby tells Nature. Drawing parallels with the cane-toad situation, he warns that more than 50 species of endemic snake could be threatened, because they are likely to eat the toxic toads. Iconic Madagascan species such as the cat-like fossa (Cryptoprocta ferox), lemurs and endemic birds are also in jeopardy. And the toads could spread diseases to other amphibians and even contaminate drinking water and transmit parasites to humans.

The species is not yet widespread in Madagascar, but it has been found a mere 25 kilometres away from the important Betampona nature reserve, and a short distance further from other internationally important biodiversity hotspots. It is unclear how fast it can travel, but cane toads have been clocked expanding their range at 50 kilometres per year. The potential tragedy is not restricted to Madagascar. “There is now a high dispersal risk of these toads spreading from Madagascar to other Indian Ocean islands such as the Mascarene Islands, Comoros and Seychelles,” says Kolby. Toads are already being collected and removed, he says, and the Madagasikara Voakajy, a non-governmental organization in Antananarivo devoted to biodiversity, is tracking the spread of the amphibians. The toads should be hunted, their spawn should be destroyed and ponds should be drained to stop their breeding, says Kolby. “We are still within the early stages of population growth,” he says. An eradication programme should be developed swiftly, “while populations are still relatively small and manageable”. Mark Hoddle, director of the Center for Invasive Species Research at the University of California, Riverside, notes that to be considered invasive, a non-native species must have established a reproductive population that spreads and causes environmental and economic damage. On this basis it may be too early to declare the Asian toad in Madagascar a problem species, he says, but there are “very good reasons to be concerned”.

Nature doi:10.1038/nature.2014.15309  Nature

June 24, 2014  Original web page at Nature



* Potential cure for captive amphibians with chytrid fungus

Researchers at Vanderbilt University have identified an alternative to a sometimes toxic therapy that protects frogs in zoos from a deadly fungal infection that has been destroying the amphibian populations worldwide. Their research is published ahead of print in Applied and Environmental Microbiology. The fungal disease, chytridiomycosis, has been decimating frogs all over the world. At present, nothing can help amphibians in the wild, but zoos currently rely on the often-toxic itraconazole to eradicate the disease from infected amphibians they wish to acquire. To preserve the most at risk amphibians, zoos have been acquiring “founding populations” of species threatened by chytridiomycosis, which is caused by the fungus, Batrachochytrium dendrobatidis. “Some species, such as the Panamanian Golden Frog, are nearly extinct in nature, and doing well only in zoos,” says Louise Rollins-Smith, a researcher on the study. “Facilities which house multiple amphibian species need safe treatments to protect their valuable colonies.” Brian Gratwicke, a conservation biologist with the National Zoo, describes the difficulties zoos face in treating the creatures. The animals must go through 10 days of immersion in an itraconazole solution. “Itraconazole is a fairly expensive drug, and depending on the species we treat we can see a very high mortality rate,” says Gratwicke. “An alternative treatment would be very helpful.” In the study, Rollins-Smith and colleagues, of Vanderbilt University, Nashville, TN, tested two potential alternatives, chloramphenicol, and amphotericin B. Although both drugs reduced B. dendrobatidis infection, neither could eradicate it. But amphotericin B had a critical advantage over chloramphenicol.

The investigators found that chloramphenicol can cause major changes in the community of microbes inhabiting amphibian skin, while amphotericin B does not, says Rollins-Smith. Previous research has shown that altering or reducing the skin microbiome leaves amphibians more vulnerable to chytridiomycosis infection, she says. Whether by competing for space, or by providing antimicrobial compounds, the skin microbiome is probably protective. Moreover, amphotericin B is much less toxic to frogs than is itraconazole. Rollins-Smith suggests that a more benign cure for chytridiomycosis might involve treatment first with amphotericin B, followed by itraconazole, which would enable a lower, less toxic dosing with the latter. “That makes sense,” says Gratwicke. “It would also correspond with my field observations.” Chytridiomycosis is a skin disease. Clinical signs include reduced appetite, weight loss, lethargy, and loss of righting reflex. Death is thought to result from disruption of sodium and potassium ion transport in the skin, resulting in osmotic imbalance and asystolic cardiac arrest. Gratwicke and others hope eventually to be able to cure chytridiomycosis with probiotic treatments that would add protective bacteria to the skin. But such efforts have yet to bear fruit. B. dendrobatidis was first identified as a threat to amphibians in 1998. There are about 7,000 amphibian species in the world, including roughly 6,000 frogs, 600-700 salamanders, and about 200 caecilians, says Gratwicke. The International Union for Conservation of Nature lists 122 “missing” species of frog, on its “red list,” most of which are likely extinct, including 90 for which chytridiomycosis is listed as the essential threat. Some salamanders and caecilians are also endangered. (Caecilians are legless borrowing creatures that look like the progeny of a mating between a snake and a worm).  Science Daily

June 10, 2014  Original web page at Science Daily


Bats use water ripples to hunt frogs

As the male túngara frog serenades female frogs from a pond, he creates watery ripples that make him easier to target by rivals and predators such as bats, according to researchers from The University of Texas at Austin, the Smithsonian Tropical Research Institute (STRI), Leiden University and Salisbury University. A túngara frog will stop calling if it sees a bat overhead, but ripples continue moving for several seconds after the call ceases. In the study, published this week in the journal Science, researchers found evidence that bats use echolocation — a natural form of sonar — to detect these ripples and home in on a frog. The discovery sheds light on an ongoing evolutionary arms race between frogs and bats. The male túngara frog (Physalaemus pustulosus), native to Central and South America, spends his nights calling from shallow ponds, attempting to attract the attention of a mate. Yet his call, which is based on a pattern of “whines” and “chucks,” inadvertently creates a multisensory display that can be exploited by both friend and foe. As the amorous amphibian calls out, his vocal sac continually inflates and deflates, like a pulsing balloon. This pulsating sac creates a visual cue, but also creates a third signal — ripples in the surface of the pond.

“A general theme of this research is that the way we communicate with any kind of a signal is by creating a disturbance in the environment,” said Mike Ryan, co-author on the study and professor in the Department of Integrative Biology at UT Austin. “When we vocalize, we’re causing changes in the air pressure around us and that’s what our ears hear. When we use visual signals, light bounces off whatever pigments we’re using and is transmitted to the receiver. Anything we do disturbs the environment, whether it’s intended as a communication signal or not.” The researchers found that frog-eating bats (Trachops cirrhosus) were much more likely to attack a target that had both frog calls and ripples radiating from it than one with frog calls and no ripples. This suggests that they can detect these ripples, most likely with echolocation. However, bats appear to lose this advantage if the area around the frog is cluttered with leaf litter, which may stop the ripples from propagating. “The interesting thing is that these frogs have evolved a strategy to escape predation,” said lead author Wouter Halfwerk, a postdoctoral researcher at UT Austin who is also affiliated with STRI and Leiden University. “When a frog detects the shadow of a bat overhead, his first defense is to stop calling immediately. Unfortunately for the frog, the water ripples created by his call do not also stop immediately. The ripples continue to emanate out for several seconds, creating a watery bull’s-eye on the frog. Bats use the ripples, thereby beating the anti-predator strategy.”

On the other hand, the ripples seem to enhance the response of rival male frogs to the initial caller. The researchers found that when a call was accompanied by ripples, other male frogs were more likely to respond than if the call was broadcast by itself. In addition, when they did respond, they did so with more gusto. If a call accompanied by water ripples was outside a male’s zone of defense, a circle about 15 cm across, rival males would call more than twice as fast as they would if they just heard the initial call by itself. If the call, again with ripples, was inside their territory rival frogs tended to call less, often stopping altogether and deflating their vocal sacs, presumably getting ready to rumble or run. Science Daily
February 18, 2014 Original web page at Science Daily