Parasitic infection may have spoiled zebrafish experiments

A common parasite that infects laboratory zebrafish may have been confounding the results of years of behavioural experiments, researchers say – but critics say the case isn’t proven.

Like the rat, the zebrafish (Danio rerio) is used in labs worldwide to study everything from the effects of drugs, to genetic diseases and disorders such as schizophrenia and autism. Since both zebrafish and people are highly social, researchers think that zebrafish may be a better lab model for some human behaviours than rodents.

Zebrafish demonstrate their preference for each other by clustering into shoals – a social behaviour that researchers measure when they want to test how drugs affect zebrafish stress and anxiety levels, as a proxy for potential human responses. But this behaviour can change when fish are infected with a neural parasite called Pseudoloma neurophilia, scientists from Oregon State University in Corvallis report in a paper published on 11 July in the Journal of Fish Diseases.

The team say that individual fish infected with P. neurophilia swim closer to each other than do non-infected fish, a behaviour that is also associated with increased stress and anxiety. The finding casts doubt on results from previous experiments, says lead study author Sean Spagnoli, a veterinary surgeon – since the infection may have scrambled researchers’ interpretations of shoaling behaviour.

Spagnoli first heard that a parasite was infecting many laboratory zebrafish when he was working at the Zebrafish International Resource Center (ZIRC) in Eugene, Oregon – a central repository which sends out zebrafish strains to researchers and also tests zebrafish health. P. neurophilia settles in the brain, spinal cord and nerves of zebrafish.

“The paper is great, as it raises some doubts about the way behaviour may be used to study brain function in zebrafish,” says Robert Gerlai, a behavioural geneticist from the University of Toronto Mississauga in Canada. But he advises not jumping to conclusions on the basis of one study. Gerlai has concerns about the work; in particular, he says, Spagnoli’s team relied on a low-tech method to measure their fish shoals, taking screen snapshots and measuring the distance between each fish rather than more precise continuous tracking. And the researchers didn’t check what else might have been affecting the zebrafish, he adds.

Elena Dreosti, a geneticist at University College London, says that the paper’s data are weak and the effects it shows are small. “Considerable additional work is needed to know if this is likely to have a significant impact on the type of behaviour research that is done by the community working with zebrafish,” she says.

But Spagnoli says that his low-tech method is all that’s needed to raise the red flag that infection can influence behaviours such as shoaling. He agrees that he hasn’t proven that the P. neurophilia is directly responsible for the changed behaviour – but says that his study suggests that shoaling changes when the parasite is present.

As many as half of all laboratory facilities may be using some infected zebrafish, according to ZIRC data from 2015 – although only 28 facilities submitted their zebrafish to the centre for health checks that year. Within a facility, infection rates hover around 7-10%; some tanks may have no infected zebrafish, but others have many, Spagnoli says.

Nuno Pereira, a zebrafish veterinarian at the Gulbenkian Science Institute in Oeiras, Portugal, says that most researchers are already aware of the importance of testing for the parasite – and Spagnoli agrees that labs have drastically improved their screening protocols.

But Spagnoli thinks that many labs may still have a significant number of fish that are infected. “I haven’t seen a single paper that stated that ‘fish used were certified pathogen-free for P. neurophilia’,” he says. The team will continue to study the parasite’s effects, he says, and is also looking at the potential influence of another common contaminant, Mycobacterium chelonae, on shoaling behaviour.

Nature doi:10.1038/nature.2016.20308  Nature  Original web page at Nature 


No blood vessels without cloche

The decade-long search by researchers worldwide for a gene, which is critical in controlling the formation of blood and blood vessels in the embryo, shows how fascinating science can be. It is more than 20 years since Didier Stainier, director at the Max Planck Institute for Heart and Lung Research in Bad Nauheim, discovered a zebrafish mutant named cloche. This mutant lacks development of both blood vessels and blood cells, and was, until now, a unique phenomenon. Now, his research group has succeeded in finding the gene responsible for it. It had quasi hidden itself at the very end of chromosome 13 and was discovered using the latest molecular biological methods. The discovery of the gene is not only of scientific interest, but could also become important for regenerative medicine.

At a very early stage of embryonic development, blood vessels and blood cells form from common progenitor cells. The timing and manner in which the blood and vessels form is regulated in a genetic program by multiple genes. This program is characterized by a cascade-like activity pattern. In the mid-nineties, during his time in the United States, Didier Stainier, Director of the Department of Developmental Genetics at the Max Planck Institute for Heart and Lung Research in Bad Nauheim, discovered in the model organism zebrafish, a mutant “possessing one of the most exciting developmental defects ever found in zebrafish,” says Sven Reischauer who, together with Oliver Stone and Alethia Villasenor, is one of the main authors of the study. Due to a genetic change in this fish, none of the genes involved in the genetic program for blood and blood vessel cells were activated. Consequently, these cells cannot develop. Stainier named the mutant “cloche” after another unique feature of the mutant, a cloche-like heart shape.

In the last two decades, various laboratories around the world took part in a real hunt for the gene behind the mutant. “Identifying Cloche was, for all of us, like solving a decades-old criminal case of genetics. However, in this case, it was not the perpetrator who was unknown but the victim, the defective gene,” says Reischauer. The Max Planck researchers in Bad Nauheim, together with international partners, have now successfully finished this hunt.

“The search was made extremely complicated due to the fact that the cloche gene is located at the very end of chromosome 13, in a telomeric region,” says Reischauer. Now, with methods, which have only recently become available (for example, CRISPR/Cas9 and TALEN), do we have the tools to analyse these areas. “In addition, we had to assume that the gene is only active prior to the time at which the lack of vascular growth is evident. This made it much more difficult to identify the embryos,” says Reischauer.

First, the Bad Nauheim researchers examined the entire portion of the genome in which they suspected cloche to be located. Analysis of data from 26,000 genes revealed 17 genes, which could be regarded as potential candidates. Then, they deactivated all of these candidate genes separately by producing knockout lines, and examined the blood vessel growth in these embryos. “Only in one case did we find the expected picture, namely that vessel growth failed to be induced. Then we were sure that we had found the cloche gene,” says Reischauer.

In additional experiments, the Max Planck scientists showed how important Cloche is for the development of blood vessels and blood cells in the embryo: It transpired that all genes which were previously known to be involved in vessel formation, are only active after Cloche has been active. Accordingly, Cloche itself controls the activity of the entire program.

This scenario was confirmed in so-called overexpression experiments in which the researchers injected pure cloche mRNA into embryos. This approach enabled them to start the program for vascular and blood cell formation at a time during embryo development at which it is not normally active. “We could, therefore, propose we had found the gene responsible for controlling the developmental program,” says Stainier.

Cloche seems to be highly conserved in nature: The gene is present even in birds. In mammals there is a closely related gene that can take over the function of cloche in the zebrafish model. Therefore, the Bad Nauheim scientists assume “that with the identification of the gene and its function, there will be great opportunities to develop new applications in the context of personalized stem cell therapy,” Stainier says.  Science Daily Original web page at Science Daily


Genetic elements that drive regeneration uncovered

If you trace our evolutionary tree way back to its roots — long before the shedding of gills or the development of opposable thumbs — you will likely find a common ancestor with the amazing ability to regenerate lost body parts.

Lucky descendants of this creature, including today’s salamanders or zebrafish, can still perform the feat, but humans lost much of their regenerative power over millions of years of evolution.

In an effort to understand what was lost, researchers have built a running list of the genes that enable regenerating animals to grow back a severed tail or repair damaged tissues. Surprisingly, they have found that genes important for regeneration in these creatures also have counterparts in humans. The key difference might not lie in the genes themselves but in the sequences that regulate how those genes are activated during injury.

A Duke study appearing April 6 in the journal Nature has discovered the presence of these regulatory sequences in zebrafish, a favored model of regeneration research. Called “tissue regeneration enhancer elements” or TREEs, these sequences can turn on genes in injury sites and even be engineered to change the ability of animals to regenerate.

“We want to know how regeneration happens, with the ultimate goal of helping humans realize their full regenerative potential,” said Kenneth D. Poss, Ph.D., senior author of the study and professor of cell biology at Duke University School of Medicine. “Our study points to a way that we could potentially awaken the genes responsible for regeneration that we all carry within us.”

Over the last decade, researchers have identified dozens of regeneration genes in organisms like zebrafish, flies, and mice. For example, one molecule called neuregulin 1 can make heart muscle cells proliferate and others called fibroblast growth factors can promote the regeneration of a severed fin. Yet, Poss says, what has not been explored are the regulatory elements that turn these genes on in injured tissue, keep them on during regeneration, and then turn them off when regeneration is done.

In this study, Poss and his colleagues wanted to determine whether or not these important stretches of DNA exist, and if so, pinpoint their location. It was already well known that small chunks of sequence, called enhancer elements, control when genes are turned on in a developing embryo. But it wasn’t clear whether these elements are also used to drive regeneration.

First, lead study author Junsu Kang, Ph.D., a postdoctoral fellow in the Poss lab, looked for genes that were strongly induced during fin and heart regeneration in the zebrafish. He found that a gene called leptin b was turned on in fish with amputated fins or injured hearts. Kang scoured the 150,000 base pairs of sequence surrounding leptin b and identified an enhancer element roughly 7,000 base pairs away from the gene.

He then whittled the enhancer down to the shortest required DNA sequence. In the process, Kang discovered that the element could be separated into two distinct parts: one that activates genes in an injured heart, and, next to it, another that activates genes in an injured fin. He fused these sequences to two regeneration genes, fibroblast growth factor and neuregulin 1, to create transgenic zebrafish whose fins and hearts had superior regenerative responses after injury.

Finally, the researchers tested whether these “tissue regeneration enhancer elements” or TREEs could have a similar effect in mammalian systems like mice. Collaborator Brian L. Black, PhD, of the University of California, San Francisco attached one TREE to a gene called lacZ that produces a blue color wherever it is turned on. Remarkably, he found that borrowing these elements from the genome of zebrafish could activate gene expression in the injured paws and hearts of transgenic mice.

“We are just at the beginning of this work, but now we have an encouraging proof of concept that these elements possess all the sequences necessary to work with mammalian machinery after an injury,” said Poss. He suspects there may be many different types of TREEs: those that turn on genes in all tissues; those that turn on genes only in one tissue like the heart; and those that are active in the embryo as it develops and then are reactivated in the adult as it regenerates.

Eventually, Poss thinks that genetic elements like these could be combined with genome-editing technologies to improve the ability of mammals, even humans, to repair and regrow damaged or missing body parts.

“We want to find more of these types of elements so we can understand what turns on and ultimately controls the program of regeneration,” said Poss. “There may be strong elements that boost expression of the gene much higher than others, or elements that activate genes in a specific cell type that is injured. Having that level of specificity may one day enable us to change a poorly regenerative tissue to a better one with near-surgical precision.”  Science Daily  Original web page at Science Daily


Fetal and newborn dolphin deaths linked to Deepwater Horizon oil spill

Scientists have finalized a four-year study of newborn and fetal dolphins found stranded on beaches in the northern Gulf of Mexico between 2010 and 2013. Their study, reported in the journal Diseases of Aquatic Organisms, identified substantial differences between fetal and newborn dolphins found stranded inside and outside the areas affected by the 2010 Deepwater Horizon oil spill.

The study team evaluated 69 perinatal common bottlenose dolphins in Alabama, Louisiana and Mississippi, the areas most affected by the spill, and 26 others found in areas unaffected by the spill. The work was conducted as part of an effort to investigate an “unusual mortality event” in the Gulf primarily involving bottlenose dolphins, beginning in early 2010 and continuing into 2014.

Scientists saw higher numbers of stranded perinatal dolphins in the spill zone in 2011 than in other years, particularly in Mississippi and Alabama, the researchers report. The young dolphins, which died in the womb or shortly after birth, “were significantly smaller than those that stranded during previous years and in other geographic locations,” they wrote.

Bottlenose dolphin gestation takes about 380 days, so perinatal dolphins that died in the early months of 2011 could have been exposed in the womb to petroleum products released the previous year, said University of Illinois veterinary diagnostic laboratory professor Kathleen Colegrove, who led the study. Colegrove works in the Chicago-based Zoological Pathology Program at the U. of I.

“Dolphin dams losing fetuses in 2011 would have been in the earlier stages of pregnancy in 2010 during the oil spill,” she said.

The researchers report that 88 percent of the perinatal dolphins found in the spill zone had lung abnormalities, including partially or completely collapsed lungs. That and their small size suggest that they died in the womb or very soon after birth — before their lungs had a chance to fully inflate. Only 15 percent of those found in areas unaffected by the spill had this lung abnormality, the researchers said.

The team also found that the spill-zone dolphins were “particularly susceptible to late-term pregnancy failures, signs of fetal distress and development of in utero infections including brucellosis,” a bacterial infection that can affect the brain, lungs, bones and reproductive function. Extensive testing found no evidence that an unusual or highly pathogenic Brucella strain was involved.

“These findings support that pregnant dolphins experienced significant health abnormalities that contributed to increased fetal deaths or deaths of dolphin neonates shortly after birth,” Colegrove said.

A previous study by many of the same researchers revealed that nonperinatal bottlenose dolphins stranded in the spill zone after the spill were much more likely than other stranded dolphins to have severe lung and adrenal gland damage “consistent with petroleum product exposure.” “These diseases in pregnant dolphins likely led to reproductive losses,” Colegrove said.

“Our new findings add to the mounting evidence from peer-reviewed studies that exposure to petroleum compounds following the Deepwater Horizon oil spill negatively impacted the reproductive health of dolphin populations living in the oil spill footprint in the northern Gulf of Mexico,” said Dr. Teri Rowles, a veterinarian with the National Oceanic and Atmospheric Administration’s Marine Mammal Health and Stranding Response Program and a co-author on the study.  Science Daily  Original web page at Science Daily


Scientists reveal how animals find their way ‘in the dark’

Scientists have revealed the brain activity in animals that helps them find food and other vital resources in unfamiliar environments where there are no cues, such as lights and sounds, to guide them.

Animals that are placed in such environments display spontaneous, seemingly random behaviors when foraging. These behaviors have been observed in many organisms, although the brain activity behind them has remained elusive due to difficulties in knowing where to look for neural signals in large vertebrate brains.

Now, in a study to be published in the journal eLife, researchers have used whole-brain imaging in larval zebrafish to discover how their brain activity translates into spontaneous behaviors. They found that the animals’ behavior in plain surroundings is not random at all, but is characterized by alternating left and right turn “states” in the brain, where the animals are more likely to perform repeated left and right turning maneuvers, respectively.

“We noted that a turn made by the zebrafish was likely to follow in the same direction as the preceding turn, creating alternating “chains” of turns biased to one side and generating conspicuous, slaloming swim trajectories,” says first author Timothy Dunn, a postdoctoral researcher at Harvard University.

“Freely swimming fish spontaneously chained together turns in the same direction for approximately five to 10 seconds on average, and sometimes for much longer periods. This significantly deviates from a random walk, where movements follow no discernible pattern or trend.”

By analyzing the relationship between spontaneous brain activity and spontaneous behavior in the larval zebrafish, the researchers generated whole-brain activity maps of neuronal structures that correlated with the patterns in the animals’ movements.

They discovered a nucleus in the zebrafish hindbrain, which participates in a simple but potentially vital behavioral algorithm that may optimize foraging when there is little information about the environment available to the animal.

As such behavioral strategies must exist in other animals that explore environments much larger than themselves, the team expects that the neural systems observed in the zebrafish must also exist in other organisms.

“Overall, our whole-brain analysis, neural activity experiments, and anatomical characterization of zebrafish revealed a circuit contributing to the patterning of a spontaneous, self-generated behavior,” explains co-first author Yu Mu, a postdoctoral researcher at Janelia Research Campus.

“As our study makes very specific predictions about this circuit, future experiments will be required to validate its critical components. It will also be interesting to see if different environmental contexts and the motivational state of zebrafish influence their spontaneous swim patterns.”   Science Daily  Original web page at Science Daily


Fish fins can sense touch

New study finds pectoral fins feel touch through a surprisingly similar biological mechanism to mammals

The human fingertip is a finely tuned sensory machine, and even slight touches convey a great deal of information about our physical environment. It turns out, some fish use their pectoral fins in pretty much the same way. And do so through a surprisingly similar biological mechanism to mammals — humans included.

In a study published in the Proceedings of the Royal Society B on Feb. 10, 2016 University of Chicago scientists have shown for the first time that pectoral fins in at least one species of fish possess neurons and cells that are exquisitely sensitive to touch. The discovery not only sheds light on the evolutionary biology of touch, it might also someday inspire new advances in the design of underwater robotics.

“It was a surprise to us that, similar to mammalian skin, fish fins are able to sense light pressure and subtle motion,” said study author Adam Hardy, graduate student in the Department of Organismal Biology and Anatomy. “This information seems to be conveyed by a type of cell important for touch in mammals, which suggests that the underlying sensory morphology may be evolutionarily conserved.”

Located just behind the gills, pectoral fins are a pair of distinctive appendages that correspond to forelimbs in four-legged animals. Usually involved in propulsion or balance during swimming, pectoral fins have evolved dramatic functions in certain species. They famously allow flying fish to fly and mudskippers to crawl, for example. Numerous studies have explored the biomechanics, evolution and development of these fins, but little is known about what role they play as a sensory mechanism.

There is evidence that fish possess the sense of proprioception, or awareness of where their fins are relative to their bodies (much like how we can tell where our arms are even with our eyes closed). Previous studies have identified fin neurons that send signals containing information about bending, movement and position back to the brain. But touch is distinct from proprioception, and as fins are almost always in motion, teasing apart the two senses in an experimental setting is difficult.

Hardy and Hale approached this challenge by focusing on the pictus catfish, a small, bottom-dwelling species native to the muddy waters of the Amazon river. Aside from a hardened, serrated spine used for defense, the pectoral fins of these fish are fairly typical — several bony rays connected by a soft membrane. However, pictus catfish don’t appear to use their pectoral fins for locomotion, which the team confirmed through high-speed camera analyses.

Without conflicting signals from fin movement and positioning, the researchers were able to isolate and study neural activity in response to touch. They applied a variety of different stimuli with the flat end of a pin and a brush to the pectoral fin, and measured the activity of neurons that are responsible for sending information back to the brain.

The team discovered that neurons not only responded when contact was made, they carried information about the degree of pressure and the motion of the brush as well. An analysis of the cellular structures of the fin revealed the presence of cells that closely resemble Merkel cells, which are associated with nerve endings in the skin of mammals and are essential for touch.

“Like us, fish are able to feel the environment around them with their fins. Touch sensation may allow fish to live in dim environments, using touch to navigate when vision is limited,” Hale said. “It raises a lot of exciting questions on how sensory cells shape the brain’s perception of environmental features, and may provide insight into the evolution of sensation in vertebrates.”

Intriguingly, this discovery could also have applications for underwater robotic design, especially in low-light environments.

“Understanding how membranous fins in fish are used to sense touch helps us identify what features are important for the design of underwater sensory membranes,” Hale said. “For example, you can envision fish-inspired sensory membranes that can be used to scan surfaces in underwater environments where light may be obscured.”

“In addition, animals use mechanical feedback to help control their limb movements,” she adds. “Instrumenting underwater robots with touch sensors may help to improve their performance, particularly when navigating through complex environments.”

The team are now studying touch sensitivity in the fins of other species of fish, such as flounders, as well as investigating the precise mechanisms for how fin neurons encode information about touch.

“One of big questions were trying to answer is whether this applies to all fish,” Hardy said. “We predicted that touch sensitive fins would be very useful for bottom-dwelling fish, but you can imagine its utility in nocturnal or deep-sea environments as well.”

The study, “Touch sensation by pectoral fins of the catfish Pimelodus pictus,” was supported by the Office of Naval Research and the National Science Foundation. Additional authors include Bailey Steinworth.  Science Daily  Original web page at Science Daily


Testing detects algal toxins in Alaska marine mammals

Toxins from harmful algae are present in Alaskan marine food webs in high enough concentrations to be detected in marine mammals such as whales, walruses, sea lions, seals, porpoises and sea otters, according to new research from NOAA and its federal, state, local and academic partners.

The findings, reported online today in the journal Harmful Algae, document a major northward expansion of the areas along the Pacific Coast where marine mammals are known to be exposed to algal toxins. Since 1998, algal toxin poisoning has been a common occurrence in California sea lions in Central California. However, this report is the first documentation of algal toxins in northern ranging marine mammals from southeast Alaska to the Arctic Ocean.

“What really surprised us was finding these toxins so widespread in Alaska, far north of where they have been previously documented in marine mammals,” said Kathi Lefebvre, a NOAA Fisheries research scientist who led the study. “However, we do not know whether the toxin concentrations found in marine mammals in Alaska were high enough to cause health impacts to those animals. It’s difficult to confirm the cause of death of stranded animals. But we do know that warming trends are likely to expand blooms, making it more likely that marine mammals could be affected in the future.”

The Wildlife Algal-toxin Research and Response Network for the West Coast (WARRN-West) tested samples from more than 900 marine mammals that were harvested or found stranded in Alaska from 2004 to 2013. Testing found the algal toxins, domoic acid and saxitoxin, present in low levels in some animals from each of the 13 marine mammal species examined, and from all regions in Alaska.

The levels of these algal toxins were well below the seafood safety regulatory limits. Gay Sheffield of the University of Alaska Fairbanks and coauthor of this study, however, warned that clams found in the stomachs of harvested walruses and bearded seals that are often eaten in several coastal communities throughout western and northern Alaska may contain algal toxins. Commonly eaten animal parts like muscle and blubber are not likely to accumulate these toxins in levels of concern for human consumption, and there is no change in the current guidance from the Alaska Department of Health regarding seafood safety.

Lefebvre highlighted the critical role the WARRN-West Network partners played by providing samples for the study. “By consistently submitting samples from stranded and harvested marine mammals, their work was essential to our research,” said Lefebvre. The WARRN-West network, funded by NOAA Fisheries with support from network partners, will continue surveillance for algal toxins in marine mammals.  Science Daily  Original web page at Science Daily


Starfish reveal the origins of brain messenger molecules

Biologists from Queen Mary University of London (QMUL) have discovered the genes in starfish that encode neuropeptides — a common type of chemical found in human brains. The revelation gives researchers new insights into how neural function evolved in the animal kingdom.

Publishing in the Royal Society journal Open Biology, the team led by Professor Maurice Elphick at QMUL’s School of Biological and Chemical Sciences report 40 new neuropeptide genes discovered for the first time in the common European starfish Asterias rubens.

One of the neuropeptides found is similar to kisspeptin, a chemical that triggers the onset of puberty in humans. Neuropeptides are small proteins that are secreted by nerve cells to act as signalling molecules, such as controlling or regulating the activity of other cells.

“We were able to determine the DNA sequences of thousands of genes that are expressed in the nervous system of the starfish,” explains first author Dr Dean Semmens, who recently completed his PhD at QMUL.

“Amongst these we found 40 genes that encode neuropeptides — some of which are the first members of neuropeptide ‘families’ to be discovered in an invertebrate animal.”

Starfish and other echinoderms, such as sea urchins and sea cucumbers, are more closely related to humans than other more commonly studied invertebrates, such as insects and provide a good model to study how molecules have evolved over hundreds of millions of years.

“Our research not only provides us with fascinating insights into the evolutionary origins of brain chemicals that affect how we feel and behave. Investigating neuropeptide evolution may also inform the development of novel drugs for therapeutic applications.”

The challenge now is understand the functions of neuropeptides in the strange five-sided bodies of starfish. Working in collaboration with researchers in Korea, a starfish neuropeptide that acts as a muscle relaxant has been discovered, as reported recently in the Journal of Neurochemistry.  Science Daily  Original web page at Science Daily


* European seafood fraud? Largest genetic study of fish labeling accuracy

Tough new policies to combat fish fraud across Europe appear to be working, according to new evidence. The largest multi-species survey of fish labelling accuracy to date indicates a marked and sudden reduction of seafood mislabelling in supermarkets, markets and fishmongers in the EU.

Scientists in six European countries tracked samples of the mostly commonly consumed fish, including cod, tuna, hake and plaice, after a series of studies going back 5 years had shown mislabelling in up to 40% of cases.

It is thought that more transparent seafood supply chains can lead to more sustainable exploitation and healthier oceans. The study is part of the LABELFISH project, supported by the EU Atlantic Area Programme and the Department for Environment, Food and Rural Affairs.

Principal Investigator Stefano Mariani, professor of conservation genetics at the University of Salford, said he was surprised at the progress made but that much remains to be investigated about the complexities of global seafood supply. Mariani and his collaborators carried out genetic testing of seafood sold in supermarkets, traditional markets and fishmongers in 19 European cities between 2013 and 2014, including Cardiff, Glasgow, Plymouth and Manchester, Dublin, Madrid, Marseille, Lisbon and Hamburg.

Species verification was carried out on fresh, frozen and tinned products labelled as cod, tuna, haddock, plaice, sole, swordfish, anchovy, hake and monkfish. Of the 1,563 DNA sequence samples examined, just 77 (4.9%) proved to be mislabelled. Most commonly mislabelled was anchovy (15.5%), hake (11.1%) and tuna (6.8%). By contrast only 3.5% of cod and 3% of haddock was mislabelled. None of the monkfish, plaice or swordfish samples was substituted with other species.

The study found little or no difference in tinned, fresh or frozen products and no significant country-associated trends. According to the samples taken, Spain had the highest rate of incorrect labelling (8.9%), followed by Portugal (6.7%), Germany (6.2%), Ireland (3.9%), the UK (3.3%) and France (2.7%).

The study, which is published (01/12/2015) in Frontiers in Ecology and the Environment, argues that the trend is due to a combination of transnational legislation, governance and public outreach, which has forced new regulation and self-regulation, and it contrasts the European ‘turn-around’ with the experience of the United States, where improvements appear more sluggish.

Professor Mariani added: “Genetic identification methods have progressively exposed the inadequacies of the seafood supply chain, raising awareness among the public, and serving as a warning to industry that malpractice will be detected. “This evidence indicates we are now on the road to greater transparency, which should help the management of exploited stocks worldwide, but further standardised studies on a greater range of food provision channels, such as restaurants and auctions, are warranted, in order to have a complete understanding of the current state of the trade.”  Science Daily  Original web page at Science Daily


Salmon is first transgenic animal to win US approval for food

Long-awaited decision authorizes a genetically engineered animal to grace US dinner tables for the first time. A fast-growing salmon has become the first genetically engineered animal to be approved for human consumption in the United States. The decision, issued by the US Food and Drug Administration (FDA) on 19 November, releases the salmon from two decades of regulatory limbo. The move was met with swift opposition from some environmental and food-safety groups.

But for advocates of the technology, the decision comes as a relief after a long and vexing wait. They say that it could spur the development of other genetically engineered animals. “It opens up the possibility of harnessing this technology,” says Alison Van Eenennaam, an animal geneticist at the University of California, Davis. “The regulatory roadblock had really been disincentivizing the world from using it.”

The genetically modified fish, called ‘AquAdvantage’ salmon, were engineered by AquaBounty Technologies of Maynard, Massachusetts, to express higher levels of a growth hormone than wild salmon. The fish grow to full size in 18 months rather than 3 years. According to proponents of the technology, these modifications mean that the fish require smaller amounts of food and other resources per kilogram of harvested fish, and that the modified salmon could ease pressure caused by heavy fishing of wild populations.

Opponents fear that engineered fish could escape from their farms and might alter natural ecosystems. They also criticize the lack of a requirement that the meat be labelled as genetically engineered.

“Huge numbers of people have said, ‘Yes, we want it labelled,’” says Jaydee Hanson, a senior policy analyst at the Center for Food Safety, an environmental-advocacy group in Washington DC. “If this is such a good product, the company itself should be saying it will label it.”

The FDA completed its food-safety assessment in 2010, and released its environmental-impact statement at the end of 2012. The long delay between the completion of those steps and a final decision led to rumours of political interference. But Laura Epstein, a senior policy analyst for the FDA’s Center for Veterinary Medicine, says that the approval took so long because it was the first of its kind. “With most products that are the first of its kind, we are very careful,” she says. The agency also had to wade through many public comments before it could issue a decision, she adds.

The FDA declined to comment on whether other applications for approval are in the regulatory pipeline. It is also unclear how the agency will handle animals that are genetically engineered using newer genome-editing technologies such as CRISPR, Van Eenennaam says

Nature doi:10.1038/nature.2015.18838  Nature  Original web page at Nature


* What powers the pumping heart?

Researchers at the Ted Rogers Centre for Heart Research have uncovered a treasure trove of proteins, which hold answers about how our heart pumps — a phenomenon known as contractility.

Led by University of Toronto Physiology Professor Anthony Gramolini and his collaborator, Professor Thomas Kislinger in the Department of Medical Biophysics, the team used high-throughput methods to identify more than 500 membrane proteins on the surfaces of cardiac contractile cells, which are likely to have a critical role in normal heart function. The proteins may also play a part in heart failure and abnormal heartbeat patterns known as arrhythmias.

“In addition to providing a new understanding of what makes our hearts pump, these findings could also help researchers uncover new information about how heart disease affects the signal pathways in our hearts. That might pave the way to find ways to prevent or reverse those changes,” says Gramolini.

During the study, the researchers found about 500 novel molecules that have been conserved throughout evolution. These molecules haven’t been studied in the heart and little is known about what they do in other tissues.

The group’s research focused on a protein called transmembrane protein 65 (Tmem65). By studying human stem cells and zebrafish using cell imaging and biochemical techniques, the researchers discovered that Tmem65 is involved in communication and electrical processes known as electrical coupling and calcium signaling. The team showed that Tmem65 regulates the connection point between adjacent cardiac contractile cells where it contributes to making the heart contract normally. Removing the protein had fatal consequences. The team also identified Tmem65 as the first critical tool for stem-cell researchers to monitor the maturation of cells in the heart’s two main chambers, known as ventricles.

“These proteins are theoretically targetable for intervention as well as basic study. In this study, our focus was on Tmem65, but there are 555 proteins that we identified and showed that they are present throughout many species and are conserved throughout evolution– at least in the mouse and the human — in the heart’s membrane-enriched contractile cells. Tmem65 was only the number-one candidate in our study, but theoretically, we have 554 other proteins to work through,” says Gramolini.

The study, published in Nature Communications, also provides the first resource of healthy human and mouse heart-cell proteins that will help scientists develop a better understanding the mechanisms involved in cardiac disease.

Gramolini says the findings are essential for understanding cardiac biology and hopes they open the door for further study into health and disease in his lab and others. “We need to figure out what all of these molecules are doing. My team and I hope our research sets the stage for other people to begin to pick up some of this work,” says Gramolini. “These are molecules that haven’t been studied, but must play some role in heart function. If a protein is conserved in evolution, generally it must have a critical function. We are very excited to look at the role of a number of these new proteins.”  Science Daily  Original web page at Science Daily


Why offspring cope better with climate change: It’s all in the genes

In a collaborative project with scientists from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, the researchers examined how the fish’s genes responded after several generations living at higher temperatures predicted under climate change.

“Some fish have a remarkable capacity to adjust to higher water temperatures over a few generations of exposure,” says Dr Heather Veilleux from the Coral CoE. “But until now, how they do this has been a mystery.” Using cutting-edge molecular methods the research team identified 53 key genes that are involved in long-term, multi-generational acclimation to higher temperatures.

“By understanding the function of these genes we can determine the biological processes that enable fish to cope with higher temperatures,” explains Dr Veilleux. “We found significantly higher levels of metabolic gene activity in fish exposed to higher temperatures for two generations, indicating that shifts in energy production are central to maintaining performance at higher temperatures.” “Immune and stress genes also responded at a higher level in the second generation, indicating that increased levels of these genes are required to allow these fish to better cope in warmer water,” Dr Veilleux says.

The project involved rearing coral reef fish at different temperatures for more than four years in purpose built facilities at James Cook University, and then testing their metabolic performance. “We used state-of-the-art genetic sequencing and bioinformatics to examine patterns of gene expression in the fish,” explains Professor Tim Ravasi from KAUST. “By correlating the patterns of gene expression with the metabolic performance of fish that had acclimated to the higher temperatures we were able to identify which genes had made this acclimation possible.”

“Surprisingly, we found that some proteins that respond to short-term thermal stress (called heat-shock proteins) did not respond over the long-term,” says Professor Philip Munday from the Coral CoE. “Heat shock proteins help maintain the structure of other essential proteins. Consequently, we thought they might also contribute to long-term acclimation to higher temperature,” Professor Munday says. “However, heat shock proteins were not involved in multigenerational acclimation to higher temperatures, suggesting that they are not good indicators of the capacity to cope with climate change.”

The study is the first to reveal the molecular processes that may help coral reef fishes and other marine species adjust to warmer conditions in the future. “Understanding which genes are involved in transgenerational acclimation, and how their expression is regulated, will improve our understanding of adaptive responses to rapid environmental change and help identify which species are most at risk from climate change and which species are more tolerant,” Dr Veilleux says. Science Daily Original web page at Science Daily


Freshwater and ocean acidification stunts growth of developing pink salmon

Pink salmon that begin life in freshwater with high concentrations of carbon dioxide, which causes acidification, are smaller and may be less likely to survive, according to a new study from UBC. The risks of ocean acidification on marine species have been studied extensively but the impact of freshwater acidification is not well understood. The study is one of the first to examine how rising carbon dioxide levels caused by climate change can impact freshwater fish.

“Most of the work on acidification has been in the ocean, yet 40 per cent of all fish are freshwater. We need to think about how carbon dioxide is affecting freshwater species,” said Colin Brauner, a professor in the Department of Zoology at UBC. “We found that freshwater acidification affects pink salmon and may impact their ability to survive and ultimately return to their freshwater spawning grounds.”

The study, published in Nature Climate Change, examined how baby salmon respond to fresh and ocean water with the levels of carbon dioxide expected 100 years in the future. Researchers monitored the salmon for ten weeks, from before they hatched to after the time they would migrate to ocean water.

Researchers found that these salmon were smaller and their ability to smell the water was reduced, which is important for returning to their spawning ground at the end of the life cycle and for sensing danger and responding to it. Once the salmon reached the age when they would typically begin their seaward migration, researchers found they were less able to use oxygen to exercise, which is likely to hurt their ability to find food, evade predators, and migrate

“The increase in carbon dioxide in water is actually quite small from a chemistry perspective so we didn’t expect to see so many effects,” said Michelle Ou, a former master’s student who is the lead author of the study. “The growth, physiology and behavior of these developing pink salmon are very much influenced by these small changes.

Brauner and Ou worked with pink salmon for their study as it’s the most abundant salmon species on the West Coast and of high economic and ecological importance. Pink salmon enter the ocean at the smallest size of all Pacific salmon and consequently may be the most sensitive to aquatic acidification. Further research is needed to examine the long-term impacts of freshwater and ocean acidification on all salmon species  Science Daily  Original web page at Science Daily


Why offspring cope better with climate change: It’s all in the genes

In a world first study, researchers at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University have unlocked the genetic mystery of why some fish are able to adjust to warming oceans.

In a collaborative project with scientists from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, the researchers examined how the fish’s genes responded after several generations living at higher temperatures predicted under climate change.

“Some fish have a remarkable capacity to adjust to higher water temperatures over a few generations of exposure,” says Dr Heather Veilleux from the Coral CoE. “But until now, how they do this has been a mystery.”

Using cutting-edge molecular methods the research team identified 53 key genes that are involved in long-term, multi-generational acclimation to higher temperatures. “By understanding the function of these genes we can determine the biological processes that enable fish to cope with higher temperatures,” explains Dr Veilleux.

“We found significantly higher levels of metabolic gene activity in fish exposed to higher temperatures for two generations, indicating that shifts in energy production are central to maintaining performance at higher temperatures.” “Immune and stress genes also responded at a higher level in the second generation, indicating that increased levels of these genes are required to allow these fish to better cope in warmer water,” Dr Veilleux says.

The project involved rearing coral reef fish at different temperatures for more than four years in purpose built facilities at James Cook University, and then testing their metabolic performance. “We used state-of-the-art genetic sequencing and bioinformatics to examine patterns of gene expression in the fish,” explains Professor Tim Ravasi from KAUST. “By correlating the patterns of gene expression with the metabolic performance of fish that had acclimated to the higher temperatures we were able to identify which genes had made this acclimation possible.”

“Surprisingly, we found that some proteins that respond to short-term thermal stress (called heat-shock proteins) did not respond over the long-term,” says Professor Philip Munday from the Coral CoE. “Heat shock proteins help maintain the structure of other essential proteins. Consequently, we thought they might also contribute to long-term acclimation to higher temperature,” Professor Munday says. “However, heat shock proteins were not involved in multigenerational acclimation to higher temperatures, suggesting that they are not good indicators of the capacity to cope with climate change.”

The study is the first to reveal the molecular processes that may help coral reef fishes and other marine species adjust to warmer conditions in the future. “Understanding which genes are involved in transgenerational acclimation, and how their expression is regulated, will improve our understanding of adaptive responses to rapid environmental change and help identify which species are most at risk from climate change and which species are more tolerant,” Dr Veilleux says.  Science Daily  Original web page at Science Daily


* The physics of swimming fish

Fish may seem to glide effortlessly through the water, but the tiny ripples they leave behind are evidence of a constant give-and-take of energy between the swimmer and its aqueous environment — a momentum exchange that propels the fish forward but is devilishly tricky to quantify. Now, new research shows that a fish’s propulsion can be understood by studying vortices in the surrounding water as individual units instead of examining the flow as a whole. Fish may seem to glide effortlessly through the water, but the tiny ripples they leave behind as they wriggle their way along are evidence of a constant give-and-take of energy between the swimmer and its aqueous environment — a momentum exchange that propels the fish forward but is devilishly tricky to quantify because of the continuous nature of a large, ever-flowing body of water.

When dealing with discrete objects it is relatively easy to compute the force that each exerts on the other. Imagine a cross-country skier propelling herself across a field using ski poles. The skier and her poles are discrete objects, and we can relatively easily compute the forces they exert on each other. But since the water around a swimming fish is continuous, it can be hard to pick out which regions of the fluid are most relevant for propulsion.

Now, a group of Swiss scientists has found that a fish’s propulsion through water can be understood by studying vortices in the surrounding water as individual units instead of examining the flow as a whole. Their technique, published June 23 in the journal Chaos, from AIP Publishing, could also be useful in other fluid dynamic analyses — for example, when studying unsteady vortices detaching from the wing of an airplane.

In a series of modeling experiments, the researchers focused on the swirls in the water nearest to the fish. “These vortices are believed to play a crucial role for the propulsion mechanism of fish. The fact that they rotate is already a clear indication that the fluid has strongly interacted with the fish,” said Florian Huhn, the lead researcher on the project.

The researchers identified discrete vortex regions in the water by detecting and tracking shapes called Lagrangian coherent structures — regions of a flow field that undergo similar experiences. Specifically, they looked at regions where the fluid formed discrete vortices — that is, places where the water moved in a self-contained pattern such that, if one were to draw an invisible loop around it, no material would cross that line.

“The closed line engulfs the fluid inside the vortex,” said Huhn. “Once we find this closed boundary, we trace back the whole fluid patch inside and can observe how it contributes to the propulsion mechanism of the fish.” Identifying these structures within the fluid makes them into a discrete space whose forces can be more easily calculated.

The team simulated these flow fields for two different types of swimming. The first was a steady movement, characterized by regular undulations. The second was an escape response known as the C-start, in which the fish quickly curves into a “C” shape before flipping outwards and propelling itself rapidly forward. The researchers found that for a steadily swimming fish, the fish’s movement can be largely attributed to momentum exchange between the fish and the discrete vortices.

For the C-start response, the vortices also explained a large part of the motion, but “an additional non-rotating jet fluid region enclosed by the vortex region is found to be crucial for the propulsion,” said Huhn. Huhn believes that his methodology may be useful in future fluid analyses as well. “Whenever a body propagates through fluid at a certain speed, be it birds and fish in nature or planes and ships in engineering, vortices are created, and the presented method can be used to track and understand the formation and evolution of the vortices,” he said. “Our findings further support the usefulness of Lagrangian coherent structures to decompose unsteady fluid flows into dynamically different regions.”  Nature  Original web page at Science Daily


Genetically modified fish on the loose?

Transgenic fish may soon enter commercial production, but little is known about their possible effects on ecosystems, should they escape containment. Further, risk-assessment efforts are often hampered by an inability to comprehensively model the fishes’ fitness in the wild, experts say. Genetically modified fish that overexpress growth hormone have been created for more than 25 years, but unlike many domesticated crops, transgenic fish have yet to enter commercial production. Because of the difficulty inherent in eradicating an established fish population, efforts are under way to model the threat posed by possible invasions.

In an article for an upcoming issue of BioScience, a team of government and academic researchers, led by Robert Devlin of Fisheries and Oceans Canada, examined the possible outcomes of an accidental release of transgenic fish. Their research points to numerous difficulties in modeling the prospective fitness and invasion potential of released transgenic fish.

The genetically modified salmonids the authors studied possess a suite of traits that may, under different conditions and at different life stages, render them more or less fit than wild-type salmon. For instance, the authors report that growth hormone-transgenic salmon exhibit enhanced feeding motivation. This altered feeding behavior could help them outcompete wild-type fish for food. However, more aggressive feeding might expose the transgenic fish to greater predation risk, thereby reducing their net fitness. Unraveling the net consequences of such opposing effects poses a significant challenge for regulators and decisionmakers, the authors say.

Also troublesome for modeling is the wide range of possible invasion scenarios. Even though many transgenic lines are expected to have reduced fitness compared with wild-type conspecifics, they could become established in alternative niches. As the authors put it, ‘Many novel genotypes in the form of invasive species can successfully establish in new ecosystems even without having a specific evolutionary history in those locations.’ Further complicating matters is the possibility of transgenic fishes’ adapting to the local habitats and selection pressures of the ecosystems they invade.

To address these wide-ranging concerns, the authors suggest a modeling approach that relies on the assessment of transgenic and surrogate strains in a broad array of conditions designed to simulate natural ecosystems. However, they caution, whether such risk assessments will sufficiently reduce uncertainty and preserve ecosystems ‘remains a significant objective for further research.’  Science Daily  Original web page at Science Daily


Evolution in action: Mate competition weeds out genetically modified fish from population

Wild-type zebrafish consistently beat out genetically modified Glofish in competition for female mates, an advantage that led to the disappearance of the transgene from the fish population over time, research has found. The study, the first to demonstrate evolutionary outcomes in the laboratory, showed that mate competition trumps mate choice in determining natural selection. Purdue University research found that wild-type zebrafish consistently beat out genetically modified Glofish in competition for female mates, an advantage that led to the disappearance of the transgene from the fish population over time.

The study, the first to demonstrate evolutionary outcomes in the laboratory, showed that mate competition trumps mate choice in determining natural selection. “Mating success is actually a stronger force of evolution than survival of the fittest,” said William Muir, professor of animal sciences. “If an organism can’t get a mate, it can’t pass its genes on. In terms of evolution, whether it survives or not doesn’t matter.”

Muir and Richard Howard, professor emeritus of biology, conducted a long-term study of mating success in mixed populations of wild-type zebrafish and Glofish — zebrafish containing a transgene cloned from a sea anemone that produces a fluorescent red protein. Although female zebrafish strongly preferred the neon red males to their brown, wild-type counterparts, the females were coerced into spawning with the wild-type males who aggressively chased away their transgenic rivals. As a result, the rate at which the red transgenic trait appeared in offspring fell rapidly over 15 generations of more than 18,500 fish and ultimately disappeared in all but one of 18 populations. “The females didn’t get to choose,” Muir said. “The wild-type males drove away the reds and got all the mates. That’s what drove the transgene to extinction.”

Except for their mating competitiveness, wild-type males and Glofish males were similar in fitness — that is, their health, fertility and lifespan — which was unexpected since genetically modifying an organism often decreases its ability to flourish, Muir said. “Natural selection has had billions of years to maximize an organism’s fitness for its environment,” he said. “Changing its genetics in any way almost always makes an organism less fit for the wild. You’ve ‘detuned’ it.” The similarity of the wild-type zebrafish and Glofish made it possible to test mate competition and mate choice simultaneously, which few studies have done, Howard said.

“I’ve lectured on evolution for 25 years and never found a study that linked the mechanisms of evolution with the pattern of evolutionary outcomes,” he said. “This study puts the whole story together.” The study also showed the effectiveness of a model Muir developed to assess the potential risk posed to natural populations by transgenic organisms. The model, which measures six fitness components, can be used to predict what would happen if a particular transgene were released in the wild. Its premise lies in a simple principle: If a transgene makes an organism fitter than wild types for an environment, it could pose a risk to natural populations or the ecosystem. If a transgene makes the organism less fit, the gene will be weeded out of the population over time.

“Darwin was right: Survival of the fittest works,” Muir said. “If we make a transgenic organism that has reduced fitness in the wild, evolution takes over and removes it. Nature experiments with mutations all the time, and it only saves the best of the best.” Based on the model, the researchers predicted that wild-type males would chase other males and females more than Glofish males would, have greater success in securing mates and produce more offspring. The laboratory findings confirmed their predictions. The study shows that if Glofish were released into the wild, the transgenic trait would eventually disappear as the result of sexual selection. Muir stressed that “the model does not say that even if we find no risks, we should release transgenic fish into the wild. It simply says what would likely happen if we did.” The model can be applied to genetically modified plants as well as animals and is one tool used by the U.S. Food and Drug Administration to assess potential risks posed by transgenic organisms, he said. Glofish are the only transgenic animals approved for sale to the public by the FDA.  Science Daily  Original web page at Science Daily


Fish and other animals produce their own sunscreen

Scientists from Oregon State University have discovered that fish can produce their own sunscreen. They have copied the method used by fish for potential use in humans. In the study published in the journal eLife, scientists found that zebrafish are able to produce a chemical called gadusol that protects against UV radiation. They successfully reproduced the method that zebrafish use by expressing the relevant genes in yeast. The findings open the door to large-scale production of gadusol for sunscreen and as an antioxidant in pharmaceuticals.

“The fact that the compound is produced by fish, as well as by other animals including birds, makes it a safe prospect to ingest in pill form,” says Professor Taifo Mahmud, lead author of the study. However, further studies will be needed to test if and how gadusol is absorbed, distributed, and metabolised in the body to check its efficacy and safety. Gadusol was originally identified in cod roe and has since been discovered in the eyes of the mantis shrimp, sea urchin eggs, sponges, and in the dormant eggs and newly hatched larvae of brine shrimps. It was previously thought that fish can only acquire the chemical through their diet or through a symbiotic relationship with bacteria.

Marine organisms in the upper ocean and on reefs are subject to intense and often unrelenting sunlight. Gadusol and related compounds are of great scientific interest for their ability to protect against DNA damage from UV rays. There is evidence that amphibians, reptiles, and birds can also produce gadusol, while the genetic machinery is lacking in humans and other mammals. The team were investigating compounds similar to gadusol that are used to treat diabetes and fungal infections. It was believed that the biosynthetic enzyme common to all of them, EEVS, was only present in bacteria. The scientists were surprised to discover that fish and other vertebrates contain similar genes to those that code for EEVS.

Curious about their function in animals, they expressed the zebrafish gene in E. coli and analysis suggested that fish combine EEVS with another protein, whose production may be induced by light, to produce gadusol. To check that this combination is really sufficient, the scientists transferred the genes to yeast and set them to work to see what they would create. This confirmed the production of gadusol. Its successful production in yeast provides a viable route to commercialisation. As well as providing UV protection, gadusol may also play a role in stress responses, in embryonic development, and as an antioxidant.

“In the future it may be possible to use yeast to produce large quantities of this natural compound for sunscreen pills and lotions, as well as for other cosmetics sold at your local supermarket or pharmacy,” says Professor Mahmud.  Science Daily  Original web page at Science Daily


Secrets of the seahorse tail revealed

A team of engineers and biologists reports new progress in using computer modeling and 3D shape analysis to understand how the unique grasping tails of seahorses evolved. These prehensile tails combine the seemingly contradictory characteristics of flexibility and rigidity, and knowing how seahorses accomplish this feat could help engineers create devices that are both flexible and strong. “The project brought together engineers who know computer modeling and biologists who can provide the evolutionary questions,” said leader of the research team, evolutionary biologist Dominique Adriaens, Ph.D., professor at Ghent University. “From a biological point of view, we want to understand how natural selection modified a relatively rigid ancestral tail covered with bony, armored plates into the complex seahorse tail, which is still completely covered in armored plates but is very flexible.” Adriaens, a member of the American Association of Anatomists (AAA), will present this research at the AAA Annual Meeting during Experimental Biology 2015.

The team used information from the muscles and bones of a real seahorse tail to develop a computer model they can use to decipher how the tail gets its remarkable traits. For example, the model allows researchers to test how specific muscles and skeletal structures contribute to the tail’s grasping movement and affect the angles of bending. The computer model allows researchers to manipulate anatomy in a way that isn’t possible with living seahorses. The output can be visualized as a 3D animation of the tail and be used to estimate the energy needed to bend the tail. The research team used thousands of 3D points from the computer model to quantify and map the seahorse’s unique armor and the muscular and skeletal system within. They then compared the anatomy of the tail to that of other fish species within the seahorse’s family, some of which do not have tails that bend or grasp. “We hypothesized that the variation in the grasping species would be much less than non-grasping fish because it would require certain building blocks to construct a tail that is flexible and rigid at the same time,” said Adriaens. “To our surprise, we found differences in the ways a grasping tail was made, based on the same skeletal and muscular elements. Although a grasping tail is highly exceptional for a fish, it evolved multiple times independently within the family that seahorses belong to.”

“Understanding the mechanisms involved in the evolution of the seahorse tail lets us eliminate engineering optimization and instead use biology as our optimization model,” Porter said. “This knowledge allows us to tweak properties to achieve desired flexibility and strength characteristics. Because the seahorse armor allows for a lot of flexibility, it would be interesting to see if we can develop armored devices that have flexibility, and while not necessarily prehensile, would have a large range of motion with multiple degrees of freedom.”

Seahorses use their strong and flexible tails to anchor themselves to plants and other materials on coral reefs or the sea floor, allowing them to hide from predators.  Science Daily  Original web page at Science Daily


Mercury levels in Hawaiian yellowfin tuna increasing

Mercury concentrations in Hawaiian yellowfin tuna are increasing at a rate of 3.8 percent or more per year, according to a new University of Michigan-led study that suggests rising atmospheric levels of the toxin are to blame. Mercury is a potent toxin that can accumulate to high concentrations in fish, posing a health risk to people who eat large, predatory marine fish such as swordfish and tuna. In the open ocean, the principal source of mercury is atmospheric deposition from human activities, especially emissions from coal-fired power plants and artisanal gold mining.

For decades, scientists have expected to see mercury levels in open-ocean fish increase in response to rising atmospheric concentrations, but evidence for that hypothesis has been hard to find. In fact, some studies have suggested that there has been no change in mercury concentration in ocean fish. By compiling and re-analyzing three previously published reports on yellowfin tuna caught near Hawaii, U-M’s Paul Drevnick and two colleagues found that the concentration of mercury in that species increased at least 3.8 percent per year from 1998 to 2008. A paper about the study is scheduled for online publication in the journal Environmental Toxicology and Chemistry on Feb. 2. The other authors are Carl Lamborg of the Woods Hole Oceanographic Institution, now at the University of California at Santa Cruz, and Martin Horgan.

“The take-home message is that mercury in tuna appears to be increasing in lockstep with data and model predictions for mercury concentrations in water in the North Pacific,” said Drevnick, an assistant research scientist at the U-M School of Natural Resources and Environment and at the U-M Biological Station. “This study confirms that mercury levels in open ocean fish are responsive to mercury emissions.” Drevnick and his colleagues reanalyzed data from three studies that sampled the same yellowfin tuna population near Hawaii in 1971, 1998 and 2008. In each of the three studies, muscle tissues were tested for total mercury, nearly all of which was the toxic organic form, methylmercury. In their re-analysis, Drevnick and his colleagues included yellowfins between 48 and 167 pounds and used a computer model that controls for the effect of fish body size. Data from 229 fish were analyzed: 111 from 1971, 104 from 1998 and 14 from 2008. The researchers found that mercury concentrations in the yellowfins did not change between the 1971 and 1998 datasets. However, concentrations were higher in 2008 than in either 1971 or 1998. Between 1998 and 2008, the mercury concentration in yellowfins increased at a rate greater than or equal to 3.8 percent a year, according to the new study. “Mercury levels are increasing globally in ocean water, and our study is the first to show a consequent increase in mercury in an open-water fish,” Drevick said. “More stringent policies are needed to reduce releases of mercury into the atmosphere. If current deposition rates are maintained, North Pacific waters will double in mercury by 2050.” Yellowfin tuna, often marketed as ahi, is widely used in raw fish dishes — especially sashimi — or for grilling. The Natural Resources Defense Council’s guide to mercury in sushi lists yellowfin tuna as a “high mercury” species. Science Daily Original web page at Science Daily


How cells communicate

During embryonal development of vertebrates, signaling molecules inform each cell at which position it is located. In this way, the cell can develop its special structure and function. For the first time now, researchers of Karlsruhe Institute of Technology (KIT) have shown that these signaling molecules are transmitted in bundles via long filamentary cell projections. Studies of zebrafish of the scientists of the European Zebrafish Resource Center (EZRC) of KIT revealed how the transport of the signaling molecules influences signaling properties. A publication in the Nature Communications journal presents the results. Organisms, organs, and tissues are complex three-dimensional systems that consist of thousands of cells of various types. During embryonal development of vertebrates, each cell requires information on the position at which it is located in the tissue. This position information enables the cell to develop a certain cell type for later execution of the correct function. This information is transmitted via signal molecules, so-called morphogenes. These morphogenes are not homogenously distributed in the tissue, their concentration varies. Various concentrations activate various genes in the target cell. The cells in the developing central nervous system receive their position information from signal molecules belonging to the family of Wnt proteins. The concentration of Wnt proteins determines whether a cell differentiates to a cell of the forebrain or of the afterbrain. “Distribution of these signal molecules has to be controlled precisely,” Dr. Steffen Scholpp, head of a research group of the KIT Institute of Toxicology and Genetics (ITG), explains. “Smallest changes of the concentration or the transport direction may cause severe damage, such as massive malformations during embryonal development or formation of cancer.” For the first time now, the working group of Dr. Steffen Scholpp has shown that the Wnt proteins are transmitted specifically via long cell projections, so-called filopodia. In the Nature Communications journal, the scientists report that the signaling factors are loaded on the tips of the filopodia only. In this way, signaling can start immediately upon contacting. The signaling factors bind to the corresponding receptors of the target cell and induce the correct cell response. “Now, the source cell can decide precisely which target cell receives how much signaling protein at which time,” Scholpp explains. The KIT researchers study zebrafish and human cell lines and succeeded in reproducing or reducing the filopodia and analyzing the resulting changes of signaling properties of the Wnt morphogenes.  Science Daily  Original web page at Science


Gray seals may be becoming the great white sharks of Dutch beaches

After 10 years of criminal scene investigation–style work, researchers have pinpointed the gray seal as the culprit behind mutilated, stranded harbor porpoises on Dutch beaches. After 10 years of criminal scene investigation–style work, researchers have pinpointed the gray seal as the culprit behind mutilated, stranded harbor porpoises on Dutch beaches. Gray seals may be becoming the great white sharks of Dutch beaches. The bodies kept washing ashore—dozens of mutilated harbor porpoises stranded on the Dutch beaches every year, their bloody remains discovered by screaming vacationers. Now, after 10 years of crime scene investigation–style work—complete with autopsies and DNA testing—biologists and veterinary pathologists have finally cracked the identity of the murderers: big-eyed, chubby-faced gray seals. The finding could lead conservationists to rethink gray seal rehabilitation, and it even raises the specter of a new “great white” in the North Sea. When harbor porpoises with missing bellies first appeared on Dutch coastlines in 2006, local biologists thought someone was deliberately hurting the animals. But the numbers soon rose to dozens a year—impossible to attribute to a single person. So the scientists looked elsewhere: Perhaps it was ducted propellers that sucked the porpoises in? Or fishermen cutting up unintentionally trapped porpoises? Then in 2012, a group of Belgian researchers noticed that some of the wounds on dead porpoises found on Belgium beaches bore the canine teeth marks of gray seals. “We thought, ‘Of course, how silly,’ ” says biologist Mardik Leopold of the Wageningen University and Research Centre in the Netherlands. “You think seals are nice, cuddly animals—they are not. They are predators.” With a towering height of 2.5 meters and the weight of two linebackers, gray seals are the largest predators in the southern North Sea. Though they are known as fish hunters, an adult male seal could easily overpower a 30-kilogram juvenile harbor porpoise. So the researchers examined photographs and autopsy results of more than 1000 stranded harbor porpoises collected from 2003 to 2013. The wounds further implicated gray seals. There was the torn blubber, the fatty nourishment that seals seek; the rows of canine teeth imprints on the tailstock, the thin part connecting the body and the tail; and the telltale scratch marks—four parallel lines left by seal claws grabbing onto the porpoises. Analysis indicates that close to a fifth of the stranded porpoises had a lethal encounter with gray seals—mostly naive juveniles who probably saw seals for the first time in their lives as they migrated north in the spring, Leopold says.

But finding the smoking gun proved to be a challenge. Short of analyzing the stomach contents of living seals, the only way to ascertain the identity of the predator was to find saliva DNA in the inflicted wounds: a seemingly impossible task, as seawater should quickly wash away any traces of DNA. Even human forensics rarely employs such analysis on drowned corpses, Leopold says. “Everyone thought we were crazy in even trying.” Indeed, nothing turned up from the obvious tear wounds. But at the bottom of deep, narrow bite marks on three porpoise bodies—where the flesh veered back after the seals pulled out their teeth and formed sealed pockets—the biologists found the iron-clad DNA evidence, they report online today in the Proceedings of the Royal Society B. That solves the “who” question, but it still doesn’t answer the “why”: What caused the gray seals to suddenly eye harbor porpoises for dinner in 2006? Humans may be to blame, the researchers suggest. As gas prices went up in recent years, Dutch fishermen switched from trolling to using cheaper set nets anchored to the seabed, which trapped harbor porpoises as by-catch. The team speculates that the gray seal, known to steal fish from the set nets, may have stumbled on a much larger, fattier “fish” and went on to actively hunt porpoises. The situation poses a dilemma for conservationists, as both the gray seals and the harbor porpoises are protected species. The Netherlands currently operates three rehabilitation centers for seals: The marine mammals disappeared from the region in the Middle Ages due to excessive hunting and only reemerged in the 1980s. But conservationists may need to reconsider the strategy, says biologist Jan Haelters of the Royal Belgian Institute of Natural Sciences in Ostend, who was not involved with the study. “In Africa, if you take care of all the lions and release them to the wild, it would affect the natural balance.” Still, he says, the study “gives us a very good framework for coordinated, coherent monitoring of harbor porpoises.” The seal predation could have long-term impacts on the local porpoise population, Leopold says. Researchers studying bottlenose dolphin attacks on porpoises in Scotland have found that the porpoises adapt by becoming leaner, faster swimmers. But speed comes at a cost. Compared with larger marine mammals such as whales, porpoises have more surface area relative to their body volume, which means they need to feed every hour to compensate for heat loss through the skin. Without food, a porpoise would die of starvation after 3 days, whereas a whale can fast for a month. “They are between a rock and a hard place really,” Leopold says. That seals would hunt down such large prey hints at a bigger problem, Leopold and Haelters warn. The Dutch shores are frequented by human bathers and surfers, raising the specter of a new “great white” terrorizing the North Sea beaches. “Statistically,” Haelters says, “an accident will happen.”  Science Magazine  Original web page at Science Magazine


First clues found in mysterious sea star die-off

A virus is the likely culprit in a massive, ongoing die-off of sea stars along the Pacific Coast of North America, researchers report on 17 November in the Proceedings of the National Academy of Sciences. Their intense, year-long investigation has zeroed in on a densovirus (from the family Parvoviridae) that has been present in the Pacific Ocean since at least 1942. But a mystery remains: why the virus seems to have suddenly bloomed into an outbreak that has devastated marine life from Alaska to Baja California. Sea-star wasting disease is a poorly understood condition in which sea stars decline from apparent good health into melted piles of goo over a matter of days. The latest outbreak emerged along the Olympic Peninsula in Washington in June 2013, where its effects were not severe. But the disease has spread rapidly to several sites along the Pacific coast, decimating populations of about 20 species of sea star. Since then, its reach has expanded, and the disease has even returned to the Olympic Peninsula with a vengeance. “We don’t seem to be at the end of this yet,” says Peter Raimondi, a marine ecologist at the University of California, Santa Cruz, and a co-author of the study. From the outbreak’s early days, anecdotal evidence pointed to a viral cause. Aquaria that sterilized the sea water in their tanks using ultraviolet light or that made their own saline tank water — such as Seattle Aquarium and the California Academy of Sciences in San Francisco — had healthy sea stars. Aquaria that used untreated or sand-filtered sea water (which excludes most bacteria and protozoa) saw their sea stars develop the telltale lesions associated with the wasting disease. Researchers examined tissues from diseased and apparently healthy individuals collected at the same sites, but saw no bacterial or protozoal infections associated with the wasting disease. Deciding to focus on viruses, they sequenced the viral DNA from samples of healthy and diseased individuals. “There really was only one group, densoviruses, that stood out as being associated with diseased tissues more than the healthy tissues,” says first author Ian Hewson, a microbial ecologist at Cornell University in Ithaca, New York. To confirm that initial finding, the team added viruses from diseased sea-star tissue to tanks of healthy sea stars. These animals became ill in about a week, whereas a control population treated with heat-killed viruses remained healthy. When a viral inoculum from the diseased stars was added to new populations, they also sickened.

“It’s pretty persuasive evidence,” says Curtis Suttle, a marine virologist at the University of British Columbia in Vancouver who was not involved in the work. Suttle says that the finding offers a window into what viruses — which are astoundingly abundant in surface sea water, at an estimated 10 million per millilitre — are doing in marine environments. “We have almost no understanding of the relationship between viral pathogens and mortality in natural sea creatures,” says Suttle. Most information that is available concerns economically important species, or those considered “charismatic macro-fauna”, such as seals, Suttle says. With the new sea-star data in hand, “at least now we can start to look” for densovirus, he adds. Now researchers hope to understand why the virus turned into a mass killer. Densovirus is not new: researchers found it in the preserved tissues of presumably healthy museum specimens dating back to the 1940s. It is also found in plankton, sediments and other marine animals, such as sea cucumbers and sea urchins. No environmental factors have been found to correlate with either the onset or the progression of the disease in regional monitoring led by Raimondi. “At this point we have no idea why something that seems have been present [in the past] has all of a sudden become so lethal,” he says. It is possible, however, that sea-star populations are on the verge of staging a comeback on their own. At Channel Islands National Park in southern California, biologists have been monitoring sea stars for more than 30 years. “I can tell you that sunflower stars are at the lowest density we’ve seen, since monitoring began,” says David Kushner, a biologist with the US National Park Service, which runs the site. “But we’re also seeing a decent number of new juveniles.” And for the moment, he says, those seem to be doing okay.

Nature doi:10.1038/nature.2014.16359  Nature  Original web page at Nature


Crustaceans win battle against being feminized

New research by scientists at the University of Portsmouth has shown that crustaceans turned partially into females retain a core of masculinity, and they may have learned how to do it after evolutionary battles with parasites. The researchers have also published the entire genetic code for the amphipod crustacean they studied, which they hope will lead to even better understanding of their biology. The research is published in Environmental Science and Technology. One of the researchers Dr Alex Ford said: “We’ve known for some time that fish change sex if they’re subjected to even small amounts of oestrogen in the water, but until now we didn’t know what was happening to crustaceans. “What we found is that once a crustacean has decided to be male, it can lock down its maleness. It will still become feminised in many respects, but at its core, it will remain male. This has important implications for how we study the effects of potential feminising pollutants on these creatures.” Fish and some other aquatic creatures are increasingly changing sex because the rivers and oceans are receiving a steady stream of feminising pollutants in sewage and industrial effluent. Dr Ford and his co-author Dr Stephen Short are marine biologists at the Institute of Marine Sciences at Portsmouth and have been studying the effect of different chemicals on a range of organisms for several years. Dr Short said: “We don’t know why crustaceans, but not vertebrates, have this ability to hold on to their male-ness, but we know crustaceans have been engaged in long evolutionary battles with feminising parasites which turn males into females in order to transmit to the next generation via the eggs of their hosts. “It could be that this history has given crustaceans strategies to cope with feminisation and this is now proving useful in the face of human pollution.” Some crustaceans decide whether to be male or female soon after hatching. It is, Dr Ford says, “a little window of plasticity.” “In fish and in humans and other mammals if a creature becomes more female, they automatically will become less male as a result. It’s like a seesaw. Crustaceans are wired differently and by becoming female, they don’t necessary lose their maleness,” he said. The research was part of a four-year project that looked at the effects of parasites and pollution on crustaceans and was funded by the Natural Environment Research Council (NERC). Dr Ford has previously found that a miniscule amount of drugs — equivalent to a drop in an Olympic sized swimming pool -commonly found in human waste can have a dramatic effect on aquatic life, including changing the speed at which some creatures can swim, to their ability to reproduce. He said: “Crustaceans are the most diverse creatures in our oceans and, until now, we didn’t know a lot about their molecular biology. “By publishing the entire set of genes we are giving biologists a whole suite of tools to further study many aspects of their biology including their endocrine, nervous and immune systems.”  Science Daily  Original web page at Science Daily


* Synthetic fish measures wild ride through dams

In the Pacific Northwest, young salmon must dodge predatory birds, sea lions and more in their perilous trek toward the ocean. Hydroelectric dams don’t make the trip any easier, with their human made currents sweeping fish past swirling turbines and other obstacles. Despite these challenges, most juvenile salmon survive this journey every year. Now, a synthetic fish is helping existing hydroelectric dams and new, smaller hydro facilities become more fish-friendly. The latest version of the Sensor Fish — a small tubular device filled with sensors that analyze the physical stresses fish experience — measures more forces, costs about 80 percent less and can be used in more hydro structures than its predecessor, according to a paper published today in the American Institute of Physics’ Review of Scientific Instruments. “The earlier Sensor Fish design helped us understand how intense pressure changes can harm fish as they pass through dam turbines,” said lead Sensor Fish developer Daniel Deng, a chief scientist at the Department of Energy’s Pacific Northwest National Laboratory. “And the newly improved Sensor Fish will allow us to more accurately measure the forces that fish feel as they pass by turbines and other structures in both conventional dams and other hydro power facilities. As we’re increasingly turning to renewable energy, these measurements can help further reduce the environmental impact of hydropower.” More than half of the United States’ renewable energy came from hydropower in 2013, representing 7 percent of the nation’s total power generation that year. The vast majority of that power came from traditional, large hydroelectric dams. Today, there is also a growing interest in small hydro facilities such as small dams that generate less than 10 megawatts of power and pumped storage hydroelectric plants. Most large dams in the U.S. were built in the 1970s or earlier and will soon need to be relicensed — a process that includes evaluating and often reducing a dam’s environmental impact. Key to that evaluation is examining how fish fare when swimming through dams. PNNL began developing the Sensor Fish in the late 1990s to improve fish survival at hydroelectric dams along the Pacific Northwest’s ColumbiaRiver Basin. The earliest design featured basic circuitry, sensors and two AA batteries encased in a six-inch-long, fish-shaped piece of clear rubber. Though the appearance was fish-like, the design didn’t fully capture the experience of real juvenile salmon swimming through dams.

High-tech solution So PNNL staff went back to the drawing board and devised the current, tubular design around 2004. Similar to the latest design, the 2004-issued Sensor Fish featured a hollow tube of clear, durable plastic that was stuffed with various sensors, a circuit board and a miniature rechargeable battery. Using this version of the device, which has been dubbed the first-generation Sensor Fish, PNNL researchers measured the various forces juvenile salmon experience as they pass through dams. Back then, the Sensor Fish was specifically designed to evaluate dams equipped with a common type of turbine along the Columbia River, the Kaplan turbine. The pressure change, they found, is akin to traveling from sea level to the top of Mount Everest in blink of an eye. Many people assume fish swimming through dams are only injured when turbine blades hit them, but PNNL’s research has shown there are many different forces that can harm fish, including abrupt pressure changes in dam turbine chambers. That knowledge is helping redesign dam turbines so they create less severe pressure changes while maintaining or even improving power production. Many of America’s aging hydroelectric dams will be undergoing retrofits in coming years that include installing newly designed turbines. The need to retrofit old dams, combined with interest in building new hydropower facilities here and abroad, triggered a redesign of the Sensor Fish about three years ago. The latest version — called the second-generation Sensor Fish — can be used in different kinds of hydro facilities, including unconventional, smaller hydropower plants and conventional dams with either Kaplan or Francis dam turbines. The new device also measures forces more precisely — it measures nearly twice as much pressure and acceleration as before, for example. And the Sensor Fish is now significantly cheaper to make: the revamped devices cost $1,200 each, while the earlier ones cost $5,000. Other features were also added, such as a temperature sensor, an orientation sensor, a radio transmitter and an automatic retrieval system that floats the device to the surface after a predetermined amount of time. Test-proven, ready for the field Researchers successfully field-tested the new and improved Sensor Fish in two Washington state dams: IceHarbor on the Snake River and Boundary on the Pend OreilleRiver. Lab tests also showed the second-generation device worked well after facing up to 600 times the force of gravity.  Science Daily  Original web page at Science Daily


Animals losing migratory routes? Devasting consequences of scarcity of ‘knowledgeable elders’

Small changes in a population may lead to dramatic consequences, like the disappearance of the migratory route of a species. Until the ’50s, bluefin tuna fishing was a thriving industry in Norway, second only to sardine fishing. Every year, bluefin tuna used to migrate from the eastern Mediterranean up to the Norwegian coasts. Suddenly, however, over no more than 4-5 years, the tuna never went back to Norway. In an attempt to solve this problem, Giancarlo De Luca from SISSA (the InternationalSchool for Advanced Studies of Trieste) together with an international team of researchers (from the Centre for Theoretical Physics — ICTP — of Trieste and the Technical University of Denmark) started to devise a model based on an “adaptive stochastic network.” The physicists wanted to simulate, simplifying it, the collective behaviour of animal groups. Their findings, published in the journal Interface, show that the number of “informed individuals” in a group, sociality and the strength of the decision of the informed individuals are “critical” variables, such that even minimal fluctuations in these variables can result in catastrophic changes to the system. “We started out by taking inspiration from the phenomenon that affected the bluefin tuna, but in actual fact we then developed a general model that can be applied to many situations of groups “on the move,” explains De Luca. The collective behaviour of a group can be treated as an “emerging property,” that is, the result of the self-organization of each individual’s behaviour. “The majority of individuals in a group may not possess adequate knowledge, for example, about where to find rich feeding grounds” explains De Luca. “However, for the group to function, it is enough that only a minority of individuals possess that information. The others, the ones who don’t, will obey simple social rules, for example by following their neighbours.”

The tendency to comply with the norm, the number of knowledgeable individuals and the determination with which they follow their preferred route (which the researchers interpreted as being directly related to the appeal, or abundance, of the resource) are critical variables. “When the number of informed individuals falls below a certain level, or the strength of their determination to go in a certain direction falls below a certain threshold, the migratory pathway disappears abruptly.” “In our networks the individuals are “points,” with interconnections that form and disappear in the course of the process, following some established rules. It’s a simple and general way to model the system which has the advantage of being able to be solved analytically,” comments De Luca. So what ever happened to the Norwegian tuna? “Based on our results we formulated some hypotheses which will, however, have to be tested experimentally,” says De Luca. In the ’50s Norway experienced a reduction in biomass and in the quantity of herrings, the main prey of tuna, which might have played a role in their disappearance. “This is consistent with our model, but there’s more to the story. In a short time the herring population returned to normal levels, whereas the tuna never came back. Why?” One hypothesis is that, although the overall number of Mediterranean tuna has not changed, what has changed is the composition of the population: “The most desirable tuna specimens for the fishing industry are the larger, older individuals, which are presumably also those with the greater amount of knowledge, in other words the knowledgeable elders.” concludes De Luca. Another curious fact: what happens if there are too many knowledgeable elders? “Too many know-alls are useless,” jokes De Luca. “In fact, above a certain number of informed individuals, the group performance does not improve so much as to justify the “cost” of their training. The best cost-benefit ratio is obtained by keeping the number of informed individuals above a certain level, provided they remain a minority of the whole population.”  Science Daily

April 15, 2014  Original web page at Science Daily



Speed trap for fish catches domestic trout moving too slow

WashingtonStateUniversity researchers have documented dramatic differences in the swimming ability of domesticated trout and their wilder relatives. The study calls into question the ability of hatcheries to mitigate more than a century of disturbances to wild fish populations. Kristy Bellinger, who did the study for her work on a Ph.D. in zoology, said traditional hatcheries commonly breed for large fish at the cost of the speed they need to escape predators in the wild. The use of hatcheries to support declining wild salmon and steelhead is controversial,” said Bellinger. “They have a role as being both a part of the solution in supplementing depleted stocks and as being a hindrance to boosting natural populations, as they often produce fish that look and behave differently from their wild relatives.” Bellinger conducted the study with Gary Thorgaard, a nationally recognized fish geneticist and professor in WSU’s School of Biological Sciences, and her advisor, Associate Professor Patrick Carter. Their work is published in the journal Aquaculture. The study used a sort of speed trap for fish, a meter-long plastic tank filled with water and fitted with electronic sensors. Over 10 weeks, Bellinger repeatedly ran 100 clonal (genetically similar) hatchery-raised and semi-wild rainbow trout through the tank, clocking their speed and monitoring their growth from week to week. The clonal rainbow trout were propagated on the WSU campus. The domesticated fish tended to grow faster. But while increased size is generally seen as a sign of fitness, the researchers saw that wasn’t the case as far as speed is concerned.

“The highly domesticated fish have bigger body sizes but slower swim speeds compared to the more wild lines that are smaller,” said Bellinger. “It is intuitive to think that the more you feed them, the more they’re going to grow, the faster they’re going to be, and that’s what we see within each clonal line. However, between the lines, the domesticated fish were larger but slower sprinters.” Over the past century, hatcheries have become a mainstay of recreational fishing, providing millions of trout and other salmonids to lakes and streams. More recently, hatcheries have come to be seen as tools in conserving native stocks. The state of Washington has more than 200 hatcheries, with most producing salmon and steelhead, an ocean-running trout, and about one-fourth producing trout and other game fish. “Fish managers want the biggest bang for their buck,” she said. “But if increased size is a tradeoff of sprint speed, as our data show, then we assume hatchery fish are being picked off by predators due to their slower speed, which makes the process of supplementing native fish with hatchery fish an inefficient tool for conservation and a waste of money.”  Science Daily

April 1, 2014  Original web page at Science Daily



Fish-kill method questioned

Common anaesthetic not the most humane option for zebrafish euthanasia, say studies. The anaesthetic MS-222, which can be added to tanks to cause overdose, seems to distress the fish, two separate studies have shown. The studies’ authors propose that alternative anaesthetics or methods should be used instead. “These two studies — carried out independently — use different methodologies to reach the same conclusion: zebrafish detect and avoid MS-222 in the water,” says Stewart Owen, a senior environmental scientist at AstraZeneca’s Brixham Environmental Laboratory in Brixham, UK, and a co-author of one of the studies. “As this is a clear aversive response, as a humane choice, one would no longer use this agent for routine zebrafish anaesthesia.” The use of zebrafish (Danio rerio) in research has skyrocketed in recent years as scientists have sought alternatives to more controversial  animal models, such as mammals. The fish are cheap and easy to keep, and although no firm data on numbers have been collected, millions are known to be housed in laboratories around the world. Nearly all will eventually be killed. MS-222 (ethyl 3-aminobenzoate methane­sulphate, also known as TMS) is one of the agents most frequently used to kill the creatures. It is listed as an acceptable method of euthanasia by many institutions, and also by societies such as the American Veterinary Medical Association. But the study by Owen and his co-authors, published last year (G. D. Readman et al. PLoS ONE 8, e73773; 2013), and the second study, published earlier this month by Daniel Weary and his colleagues at the University of British Columbia in Vancouver, Canada (D. Wong et al. PLoS ONE 9, e88030; 2014), show that zebrafish seem to find the chemical distressing.

The research should fundamentally change the practice, say the authors of both papers. Owen’s study used video tracking to measure whether zebrafish avoided anaesthetics flowing through one side of a tank by moving to the other, untreated side. In the case of MS-222, the team found that zebrafish spent significantly more time in the untreated side than on the side containing the anaesthetic. Weary’s team allowed zebrafish to first spend time in either a light or a dark section of a tank, and then exposed them to MS-222 on their preferred side, the light side. After exposure to the anaesthetic, all but one of 17 fish in the study spent less time on the light side, and nine completely avoided it. This indicates that the fish would rather undergo discomfort — in this case, darkness — than be exposed to MS-222. “There must be something unpleasant” about MS-222 to produce such a strong signal in the experiment, says Weary, because fish do not avoid many other harmful chemicals to such an extent. “The results are pretty clear,” he adds. “We’re at a stage where it is a matter of getting policy-makers and researchers to think about this and to rethink the procedures.” There is growing debate over the most humane methods of killing laboratory mammals, with rodent euthanasia coming under increased scrutiny. Fish euthanasia has so far attracted less attention. “I think of fish welfare as being 10 to 20 years behind mammal welfare,” says Lynne Sneddon, who studies welfare in fish and is director of bioveterinary science at the University of Liverpool, UK. Sneddon says the two papers convincingly show that the use of MS-222 to kill zebrafish should probably be avoided. But she notes that there are significant differences between species — data on zebrafish should not be generalized to other laboratory fish, such as salmonids, for example — and therefore cautions against banning its use in the animals entirely.

Zoltan Varga, director of the Zebrafish International Resource Center at the University of Oregon in Eugene, also cautions against abandoning MS-222 because the optimal method of killing will depend heavily on the individual experiment and set-up. “A choice of anaesthetics is critical, as there is a range of reactions possible and we need to administer drugs that address any situation,” he says. In some cases, this could be MS-222. There is not enough evidence to know which is the most humane method, and opinions differ. Owen suggests using the anaesthetic etomidate, which is cheaper than MS-222 (US$0.15 per litre compared with $0.23 per litre of working solution) and which seemed to be less aversive in his tests. Weary’s research suggests clove oil as another cheap alternative. Varga favours ‘hypothermal shock’ — in which the zebrafish, a tropical species, are rapidly cooled. This method is illegal in the United Kingdom owing to concerns that ice may damage fish tissue while the animals are still conscious. As the number of fish experiments continues to rise — they are the second most popular research species in the United Kingdom — the question grows in importance. “We must have the patience to allow the zebrafish field research time to critically explore what the best — that is, most humane — standards are,” says Varga. “We can neither infer these standards from human experience nor from the guidelines and regulations already established for other laboratory organisms.”  Nature

March 18, 2014  Original web page at Nature


Scientists find cell fate switch that decides liver, or pancreas?

Harvard stem cell scientists have a new theory for how stem cells decide whether to become liver or pancreatic cells during development. A cell’s fate, the researchers found, is determined by the nearby presence of prostaglandin E2, a messenger molecule best known for its role in inflammation and pain. The discovery, published in the journal Developmental Cell, could potentially make liver and pancreas cells easier to generate both in the lab and for future cell therapies. Wolfram Goessling, MD, PhD, and Trista North, PhD, both principal faculty members of the Harvard Stem Cell Institute (HSCI), identified a gradient of prostaglandin E2 in the region of zebrafish embryos where stem cells differentiate into the internal organs. Experiments conducted by postdoctoral fellow Sahar Nissim, MD, PhD, in the Goessling lab showed how liver-or-pancreas-fated stem cells have specific receptors on their membranes to detect the amount of prostaglandin E2 hormone present and coerce the cell into differentiating into a specific organ type. “Cells that see more prostaglandin become liver and the cells that see less prostaglandin become pancreas,” said Goessling, a Harvard Medical School Assistant Professor of Medicine at Brigham and Women’s Hospital and Dana-Farber Cancer Institute. “This is the first time that prostaglandin is being reported as a factor that can lead this fate switch and essentially instruct what kind of identity a cell is going to be.”

The researchers next collaborated with the laboratory of HSCI Affiliated Faculty member Richard Maas, MD, PhD, Director of the Genetics Division at Brigham and Women’s Hospital, to see whether prostaglandin E2 has a similar function in mammals. Richard Sherwood, PhD, a former graduate student of HSCI Co-director Doug Melton, was successfully able to instruct mouse stem cells to become either liver or pancreas cells by exposing them to different amounts of the hormone. Other experiments showed that prostaglandin E2 could also enhance liver growth and regeneration of liver cells. Goessling and his research partner North, a Harvard Medical School Assistant Professor of Pathology at BethIsraelDeaconessHospital, first became intrigued by prostaglandin E2 in 2005, as postdoctoral fellows in the lab of HSCI Executive Committee Chair Leonard Zon, MD. It caught their attention during a chemical screen exposing 2,500 known drugs to zebrafish embryos to find any that could amplify blood stem cell populations. Prostaglandin E2 was the most successful hit — the first molecule discovered in any system to have such an effect — and recently successfully completed Phase 1b clinical trials as a therapeutic to improve cord blood transplants. “Prostaglandin might be a master regulator of cell growth in different organs,” Goessling said. “It’s used in cord blood, as we have shown, it works in the liver, and who knows what other organs might be affected by it.” With evidence of how prostaglandin E2 works in the liver, the researchers next want to calibrate how it can be used in the laboratory to instruct induced pluripotent stem cells — mature cells that have been reprogrammed into a stem-like state — to become liver or pancreas cells. The scientists predict that such a protocol could benefit patients who need liver cells for transplantation or who have had organ injury.  Science Daily March 4, 2014  Original web page at Science Daily


Genetic chip will help salmon farmers breed better fish

Atlantic salmon production could be boosted by a new technology that will help select the best fish for breeding. The development will enable salmon breeders to improve the quality of their stock and its resistance to disease. A chip loaded with hundreds of thousands of pieces of DNA — each holding a fragment of the salmon’s genetic code — will allow breeders to detect fish with the best genes. It does so by detecting variations in the genetic code of each individual fish — known as single nucleotide polymorphisms (SNPs). These variations make it possible to identify genes that are linked to desirable physical traits, such as growth or resistance to problematic diseases, for example sea lice infestations. Salmon breeders will be able to carry out the test by taking a small sample of fin tissue. The chip carries over twenty times more genetic information than existing tools. Similar chips have already transformed breeding programmes for land-farmed livestock including cattle and pigs. Salmon farming contributes around half a billion pounds to the UK economy each year and provides healthy, high quality food. Worldwide, approximately 1.5 million tonnes of Atlantic salmon are produced every year. Dr Ross Houston, of The Roslin Institute, said: “Selective breeding programmes have been used to improve salmon stocks since the 1970s. This new technology will allow the best breeding fish to be selected more efficiently and accurately, particularly those with characteristics that are difficult to measure such as resistance to disease” Dr Alan Tinch, director of genetics at Landcatch Natural Selection, said: “This development takes selective breeding programmes to a whole new level. It is an extension to the selective breeding of salmon allowing more accurate identification of the best fish to create healthier and more robust offspring.”  Science Daily March 4, 2014  Original web page at Science Daily