Tag: Anatomy

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New discovery on how the inner ear works

Researchers have found that the parts of the inner ear that process sounds such as speech and music seem to work differently than other parts of the inner ear. Researchers from Linköping University are part of the team behind the discovery.

“This helps us understand the mechanisms that enable us to perceive speech and music. We hope that more knowledge about the capabilities of the ear will lead to better treatments for the hearing impaired,” says Anders Fridberger, professor of neuroscience at Linköping University.

To perceive speech and music, you must be able to hear low-frequency sound. And to do this, the brain needs information from the receptors, which are located close to the top of the cochlea, the spiral cavity in the inner ear. This part of the inner ear is difficult to study, as it is embedded in thick bone that is hard to make holes in, without causing damage. Now the international research team has been able to measure, in an intact inner ear, how the hearing organ reacts to sound. The results have been published in PNAS, the Proceedings of the National Academy of Sciences.

To measure in the hearing organ, the researchers used optical coherence tomography, a visualization technology for biological matter that is often used to examine the eye.

“We have been able to measure the inner ear response to sound without having to open the surrounding bone structures and we found that the hearing organ responds in a completely different way to sounds in the voice-frequency range. It goes against what was previously thought of how the inner ear works.

https://www.sciencedaily.com/ Science Daily

https://www.sciencedaily.com/releases/2016/07/160711092510.htm Original web page at Science Daily

 

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Infant bodies were ‘prized’ by 19th century anatomists, study suggests

A new study of the University of Cambridge anatomy collection suggests that the bodies of foetuses and babies were a “prized source of knowledge” by British scientists of the 18th and 19th centuries, and were dissected more commonly than previously thought and quite differently to adult cadavers.

Historical research combined with the archaeological assessment of collection specimens shows that foetus and infant cadavers were valued for the study of growth and development, and were often kept in anatomical museums.

Researchers say that socio-cultural factors and changes in the law, as well as the spread of infectious disease during the industrial revolution, dictated the availability of these small bodies for dissection.

The study, conducted by Jenna Dittmar and Piers Mitchell from Cambridge’s Department of Archaeology and Anthropology, is the first to look specifically at how British scientists investigated the changing anatomy of childhood during the 1800s. The findings are published today in the Journal of Anatomy.

The researchers undertook studies of the skeletal collection retained from the former dissecting room of Cambridge’s department of anatomy, with specimen dates ranging from 1768 to 1913.

While the bodies of adults typically underwent a craniotomy — opening of the top of the skull using a saw — the researchers found that anatomists generally kept the skulls of foetuses and young children in one piece. From a total of 54 foetal and infant specimens in the collection, just one had undergone a craniotomy.

Careful study of the bone surface revealed that soft tissues had been gently removed using knives and brushes in order to preserve as much of the bones of the head as possible, although surgical instruments would have been similar to those used on the fully-grown. Tools for other purposes in adults, such as ‘bone nipper’ forceps, were likely used for dividing diminutive ribcages.

The research suggests that anatomists kept the skeletal remains of foetuses and infants for further study and use as teaching aids, whereas adults were frequently reburied after dissection.

“Foetal and infant bodies were clearly valued by anatomists, illustrated by the measures taken to preserve the remains intact and undamaged,” says Dittmar.

“The skulls appear to have been intentionally spared to preserve them for teaching or display. This may explain why so few children with signs of dissection on their bones have been recovered from the burial grounds of hospitals or parish churches, compared with adults.”

Literature from the late 18th century shows that the size of infant bodies made them preferable for certain ‘anatomical preparations’ in teaching, particularly for illuminating the anatomy of the nervous and circulatory systems, which required an entire body to be injected with coloured wax and displayed.

“The valuable and unique knowledge that could only be obtained from the examination of these developing bodies made them essential to the study of anatomy,” says Dittmar.

“During much of the 18th and 19th century, executed criminals provided the main legal access to cadavers, and it was previously thought that dissection of young children was relatively rare. However, changes in the law may have resulted in infant dissections becoming more common.”

The Murder Act in 1752 gave the judiciary power to allow executed murderers — almost entirely men — to be used for medical dissection. These felons hardly made a dent in the growing demand for bodies, and a black market flourished.

Bodies acquired (often grave robbed) by gangs of ‘resurrectionists’, or body-snatchers, were usually sold by the inch, so those of infants were not very profitable, although there are records of ‘smalls’ being traded.

The Anatomy Act of 1832 allowed workhouses and hospitals to donate the bodies of the poor if unclaimed by family, in an attempt to abate the resurrectionists. Infectious diseases such as cholera and tuberculosis were common killers during the industrial revolution, and a major cause of infant death in hospitals and beyond. Workhouses were desperate places, and nearly always lethal to infants.

Until 1838, a legal loophole did not require a stillborn baby to be registered, and a body could be easily sold to an anatomist through an intermediary. But the New Poor Law Amendment Act of 1834 may have had the most significant repercussions of any law for infant material in anatomy collections, say the researchers.

The Act ended parish relief for unmarried women and the availability of assistance from the father of an illegitimate child. Part of Victorian society’s attempt to curtail the illegitimate birth rate, the law succeeded only in contributing to dire situations for poor unwed women, mainly in service positions, who fell pregnant.

“This left very few options for these women: the workhouse, prostitution, abortion and infanticide — all of which were life-threatening,” says Mitchell. By the 1860s, infanticide in England had reached epidemic proportions.

“Our research shows that the major sources of the bodies of very young children were from stillborn babies of destitute mothers, babies who died from infectious diseases, those dying in charitable hospitals, and unmarried mothers who secretly murdered their new-born to avoid the social stigma of single parenthood,” says Mitchell.

“Poor and desperate women at the time of the industrial revolution could not only save the cost of a funeral by passing their child’s body to an anatomist, but also be paid as well. This money would help feed poor families, so the misfortune of one life lost could help their siblings to survive tough times.”

https://www.sciencedaily.com/  Science Daily

https://www.sciencedaily.com/releases/2016/06/160630214457.htm  Original web page at Science Daily

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New view of brain development: Striking differences between adult and newborn mouse brain

Findings reveal mismatch between neuronal activity and blood flow in the brains of newborn mice, shedding new light on how the growing brain feeds itself.

Columbia scientists have found that spikes in the activity of neurons in young mice do not spur corresponding boosts in blood flow — a discovery that stands in stark contrast to the adult mouse brain. This new study raises questions about how the growing human brain meets its energy needs, as well as how best to track brain development with functional magnetic resonance imaging, or fMRI, which relies on blood-flow changes to map neuronal activity in the brain. The research could also provide critical new insights for improving care for infants.

“In the adult brain, neuronal activity triggers a localized boost in blood flow. This relationship between neuronal activity and blood flow has long been assumed to be present from birth, but our findings in mice suggest the opposite: that instead it develops over time,” said Elizabeth Hillman, PhD, a principal investigator at Columbia’s Mortimer B. Zuckerman Mind Brain Behavior Institute, associate professor of biomedical engineering and radiology at Columbia’s Fu Foundation School of Engineering and Applied Science and the paper’s senior author. Our study further suggests that this process is an essential part of building a healthy brain and could represent an unexplored factor in brain disorders that emerge in early childhood.”

Today’s study was motivated by previous fMRI studies in humans that reported vastly different responses in the brains of babies compared to the brains of adults.

“No one knew how to interpret blood-flow responses in the developing brain,” said Mariel Kozberg MD, PhD, a recent Columbia neurobiology graduate in Dr. Hillman’s lab and the paper’s first author. In this study, we needed to find out what was different between adult and newborn brains. Were the differences in neural activity itself, or did they lie in the relationship between this activity and local blood flow changes?”

To answer this question, Drs. Hillman and Kozberg developed a new imaging technique that simultaneously recorded neuronal activity and blood flow in the brains of mice of different ages (from newborn up to adult), tracking how the brain responded when they stimulated each animal’s hind paw.

“When we started to get data we were amazed by what we could see,” said Dr. Kozberg. First, the team’s innovative imaging methods revealed that, for the youngest mice, stimulating the hind paw caused a strong neuronal response, but this response was localized to one region. Then, as the animals got older, the neuronal response began to spread. By 10 days of age, stimulating the right paw first sparked activity on the left side of the brain before traveling to the right side, corresponding to the development of connections between the two hemispheres.

“We realized we were actually watching cells form connections with each other throughout the brain: the development of neural networks,” added Dr. Hillman, who is also a member of the Kavli Institute for Brain Science at Columbia.

The researchers’ second finding was even more startling. In the youngest mice, neuronal activity did not trigger an increase in blood flow, as occurs in the adult mouse brain. But as the animals matured, and their neural networks became more established, the brain’s blood-flow response gradually got stronger over time until the animal reached adulthood.

“It was like the brain was gradually learning to feed itself,” said Dr. Hillman, who notes that this finding makes a lot of sense. “It is hardly surprising that blood vessels — and the machinery linking them to brain activity — would mature in step with the development of neural activity itself.”

However, these results raised a worrying question. The job of blood vessels is to deliver oxygen-rich blood to the brain. So, can the newborn brain truly function and grow without subsequent increases in blood flow? To find out, Drs. Kozberg and Hillman used another optical imaging technique, called flavoprotein imaging, which measures how the newborn brain used oxygen.

“In the youngest animals, we confirmed that neurons were indeed consuming oxygen, but without a rush of fresh blood, they seemed to run out of fuel,” said Dr. Kozberg. “We further found that the neural activity actually caused localized drops in oxygen levels, known as hypoxias.”

Drs. Hillman and Kozberg propose several explanations for this surprising result. “Newborns make an incredible transition from being inside the womb to breathing air in the delivery room,” noted Dr. Hillman. “To survive those first few hours, the newborn brain must be well prepared to withstand enormous fluctuations in the availability of oxygen.”

Because the hypoxias seen in young mice appear to be part of the normal development process, the authors propose that it may in fact serve an important purpose.

“We know that a lack of oxygen can trigger the growth of blood vessels,” said Dr. Kozberg. “So in this case, neural activity in the newborn brain might actually be guiding blood vessels to grow in the right places.”

Moving forward, the team is preparing to compare their results in mice to the human brain. Dr. Hillman is working with researchers at Columbia’s Department of Psychiatry to analyze hundreds of fMRI scans previously collected from newborns, as well as from children of different ages.

“If we can find the same signatures of neurovascular development in human infants, we could turn fMRI into an even more powerful tool. For example, using it to better understand, detect and track the origins of developmental disorders in the newborn brain,” she said.

Dr. Hillman’s team is also eager to continue studying oxygen metabolism in newborns. Preterm infants exposed to high oxygen levels can suffer from retinopathy, a condition in which blood vessels in the eyes grow incorrectly. She hypothesizes that excessive oxygen could lead to the same disruptions to blood-vessel growth in the brain itself.

Added Dr. Hillman, “If we can learn more about the unique metabolic state of the developing brain, we might be able to improve treatment strategies for premature infants, while also gaining a deeper understanding of normal and abnormal brain development overall.”

https://www.sciencedaily.com/  Science Daily

https://www.sciencedaily.com/releases/2016/06/160621193102.htm Original web page at Science Daily

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Mental abilities are shaped by individual differences in the brain

Everyone has a different mixture of personality traits: some are outgoing, some are tough and some are anxious. A new study suggests that brains also have different traits that affect both anatomical and cognitive factors, such as intelligence and memory.

“A major focus of research in cognitive neuroscience is understanding how intelligence is shaped by individual differences in brain structure and function,” said study leader Aron K. Barbey, University of Illinois neuroscience professor and Beckman Institute for Advanced Science and Technology affiliate.

For years, cognitive neuroscientists have tried to find relationships between specific areas of the brain and mental processes such as general intelligence or memory. Until now, researchers have been unable to successfully integrate comprehensive measures of brain structure and function in one analysis. Barbey and his team measured the size and shape of features all over the brain.

“We were able to look at nerve fiber bundles, white-matter tracts, volume, cortical thickness and blood flow,” said Patrick Watson, a postdoctoral researcher at the Beckman Institute and first author of the paper. “We also were able to look at cognitive variables like executive function and working memory all at once.”

Using a statistical technique called independent component analysis, the researchers grouped measures that were related to each other into four unique traits. Together, these four traits explained most of the differences in the anatomy of individuals’ brains. The traits were mostly driven by differences in brain biology, including brain size and shape, as well as the individual’s age. The factors failed to explain differences in cognitive abilities between people. The researchers then examined the brain differences that were unexplained by the four traits. These remaining differences accounted for the individual differences in intelligence and memory.

“We were able to identify cognitive-anatomical characteristics that predict general intelligence and account for individual differences in a specific brain network that is critical to intelligence, the fronto-parietal network,” Barbey said.

The four traits reported in this study are a unique way to examine how brains differ between people. This knowledge can help researchers study subtle differences linked to cognitive abilities, Watson said.

“Brains are as different as faces, and this study helped us understand what a ‘normal’ brain looks like,” Watson said. “By looking for unexpected brain differences, we were able to home in on parts of the brain related to things like memory and intelligence.”

The researchers released their data to the public through an online platform called Open Science Framework to encourage comprehensive studies of brain structure and function.

https://www.sciencedaily.com/  Science Daily

https://www.sciencedaily.com/releases/2016/02/160225153817.htm  Original web page at Science Daily

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Chimpanzee personality linked to anatomy of brain structures

Chimpanzees’ personality traits are linked to the anatomy of specific brain structures, according to researchers at Georgia State University, The University of Texas MD Anderson Cancer Center and University of Copenhagen.

The findings, published online in the journal NeuroImage in August, reveal that both gray- matter volumes of various frontal cortex regions and gray-matter volume asymmetries (larger right versus left or vice versa) are associated with various personality traits. The results suggest the frontal cortex and asymmetries in this region of the brain play an important role in the neurobiological foundation of broad personality traits.

“Our results confirm the importance of neuroscientific approaches to the study of basic personalities and suggest that when compared to humans many of these associations are comparable in chimpanzees,” said Robert Latzman, assistant professor in the Department of Psychology at Georgia State.

The researchers studied 107 chimpanzees’ brains using magnetic resonance image (MRI) scans and also assessed each chimpanzee’s personality by using a 41-item personality questionnaire. They found chimpanzees who were rated as higher for the personality traits of openness and extraversion had greater gray-matter volumes in the anterior cingulate cortex in both hemispheres of the brain. Chimpanzees who were rated as higher on dominance had larger gray-matter volumes in the left anterior cingulate cortex and right prefrontal cortex. Chimpanzees who rated higher on reactivity/unpredictability had higher gray-matter volumes in the right mesial prefrontal cortex.

All chimpanzees received MRI scans during their annual physical examination. For the personality questionnaire, the chimpanzees were rated by staff members who had worked with the animals for an extended period and felt they had enough experience for an accurate rating. Each item consisted of a single trait with a behavioral definition and a scale ranging from “least descriptive of the chimpanzee” to “most descriptive of the chimpanzee.” The instrument consisted of five dimensions: extraversion, openness, agreeableness, dominance (opposite to the human trait of neuroticism) and reactivity/undependability (a dimension that includes content from the opposite side of the human traits of conscientiousness, agreeableness and extraversion.

Previous studies by this group suggest the existence of largely similar personality traits in humans and chimpanzees, but until this study, researchers had not explored the neuroanatomical basis of these traits in nonhuman primates.

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2015/09/150929092738.htm  Original web page at Science Daily

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How do vertebrates take on their form?

A simple physical mechanism that can be assimilated to folding, or buckling, means that an unformed mass of cells can change in a single step into an embryo organized as a typical vertebrate. This is the main conclusion of work by a team involving physicists from the Laboratoire Matière et Systèmes Complexes (CNRS/Université Paris Diderot) and a biologist from the Laboratoire de Biologie du Développement (CNRS/UPMC). Thanks to microscopic observations and micromechanical experiments, the scientists have discovered that the pattern that guides this folding is present from the early stages of development. The folds that will give a final shape to the animal form along the boundaries between cell territories with different properties. This work has shed light on the mechanism for the formation of vertebrates and thus how they appeared during evolution. These findings are published on the website of the European Physical Journal E, on 12 February 2015.

How has evolution produced a structure as complicated as a vertebrate, organized along an anterior-posterior axis, marked dorsally by the nervous system and ventrally by the digestive tract, and displaying almost perfect left-right symmetry? And how, during embryonic development, does this develop from a mass of round cells into an organized embryo? By working on chicken embryos, a team involving physicists and a biologist has managed to explain this transition by means of a relatively simple physical mechanism. The scientists worked on chicken embryos because at this development stage, they constitute the model that is closest to human embryos. Furthermore, its flat, disk-shaped structure facilitates the observation and modeling of cell movements.

A chicken embryo is made up of four concentric rings. Under the microscope, each ring looks like a series of cells of homogenous size; their size increases from the center towards the peripheral rings, with a “stepped” change from one ring to another. Not only will these cellular domains form different tissues (nervous, muscle, digestive, etc.) but, as discovered by the scientists when filming development of the embryo, it always folds at the boundary between two neighboring rings, as from the second day of its development. These folds will result in a three-dimensional shape, typical of vertebrates. By measuring the stiffness of the tissues, the scientists were then able to confirm that these boundaries between cell domains display an elastic contrast. The stiffness becomes increasingly marked when the cells are smaller, towards the center of the embryo. Thus as soon as adequate force is applied, the softer, peripheral regions (flanks) “naturally” wrap themselves around the central, stiffer region (the future central nervous system). The force in question is generated by the migration of certain cells, which stretches the embryo lengthwise.

These findings thus offer an explanation for the coupling of cell differentiation and morphogenesis (acquisition by the embryo of its shape), so that a well-formed animal containing territories with different and physically separated functions, emerges “naturally.” Understanding this process fills a conceptual gap between a shapeless mass of cells and an “animal archetype,” and sheds new light on how vertebrates have emerged during evolution. The size of cells varies abruptly from one ring to another, increasing from 5 to 10 to 15 and then 20 micrometers in diameter.

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http://www.sciencedaily.com/releases/2015/02/150216064745.htm

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* Unexpectedly speedy expansion of human, ape cerebellum

A new study published in the Cell Press journal Current Biology on October 2 could rewrite the story of ape and human brain evolution. While the neocortex of the brain has been called “the crowning achievement of evolution and the biological substrate of human mental prowess,” newly reported evolutionary rate comparisons show that the cerebellum expanded up to six times faster than anticipated throughout the evolution of apes, including humans. The findings suggest that technical intelligence was likely at least as important as social intelligence in human cognitive evolution, the researchers say. “Our results highlight a previously unappreciated role of the cerebellum in ape and human brain evolution that has the potential to refocus researchers’ thinking about how and why the brains in these species have become distinct and to shift attention away from an almost exclusive focus on the neocortex as the seat of our humanity,” says Robert Barton of Durham University in the United Kingdom. The cerebellum had been seen primarily as a brain region involved in movement control, adds Chris Venditti of the University of Reading. But more recent evidence has begun to suggest that the cerebellum has a broader range of functions. The cerebellum also contains an intriguingly large number of densely packed neurons. “In humans, the cerebellum contains about 70 billion neurons — four times more than in the neocortex,” Barton says. “Nobody really knows what all these neurons are for, but they must be doing something important.” The neocortex had gotten most of the attention in part because it is such a large structure to begin with. As a result, in looking at variation in the size of various brain regions, the neocortex appeared to show the most expansion. But much of that increase in size could be explained away by the size of the animal as a whole. Sperm whales have a neocortex that is proportionally larger than that of humans, for example. By using a comparative method that controlled for those differences in the way the two brain structures correlate, Barton and Venditti uncovered a striking pattern: both nonhuman apes and humans depart from the otherwise tight correlation in size between the cerebellum and neocortex found across other primates due to relatively rapid evolutionary expansion of the cerebellum. Barton and Venditti say that the cerebellum seems to be particularly involved in the temporal organization of complex behavioral sequences, such as those involved in making and using tools, for instance. Interestingly, evidence is now emerging for a critical role of the cerebellum in language, too.

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/10/141002123629.htm  Original web page at Science Daily

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Animals first flex their muscles: Earliest fossil evidence for animals with muscles

A new fossil discovery identifies the earliest evidence for animals with muscles. An unusual new fossil discovery of one of the earliest animals on earth may also provide the oldest evidence of muscle tissue — the bundles of cells that make movement in animals possible.

The fossil, dating from 560 million years ago, was discovered in Newfoundland, Canada. On the basis of its four-fold symmetry, morphological characteristics, and what appear to be some of the earliest impressions of muscular tissue, researchers from the University of Cambridge, in collaboration with the University of Oxford and the Memorial University of Newfoundland, have interpreted it as a cnidarian: the group which contains modern animals such as corals, sea anemones and jellyfish. The results are published today (27 August) in the journal Proceedings of the Royal Society B. Historically, the origin, evolution and spread of animals has been viewed as having begun during the Cambrian Explosion, a period of rapid evolutionary development starting 541 million years ago when most major animal groups first appear in the fossil record. “However, in recent decades, discoveries of preserved trackways and chemical evidence in older rocks, as well as molecular comparisons, have indirectly suggested that animals may have a much earlier origin than previously thought,” said Dr Alex Liu of Cambridge’s Department of Earth Sciences, lead author of the paper. “The problem is that although animals are now widely expected to have been present before the Cambrian Explosion, very few of the fossils found in older rocks possess features that can be used to convincingly identify them as animals,” said Liu. “Instead, we study aspects of their ecology, feeding or reproduction, in order to understand what they might have been.” The new fossil, named Haootia quadriformis, dates from the Ediacaran Period, an interval spanning 635 to 541 million years ago. It differs from any previously described Ediacaran fossil, as it comprisesof bundles of fibres in a broadly four-fold symmetrical arrangement: a body plan that is similar to that seen in modern cnidarians. The researchers determined that the similarities between Haootia quadriformis and both living and fossil cnidarians suggest that the organism was probably a cnidarian, and that the bundles represent muscular tissue. This would make it not only a rare example of an Ediacaran animal, but also one of the oldest fossils to show evidence of muscle anywhere in the world. “The evolution of muscular animals, in possession of muscle tissues that enabled them to precisely control their movements, paved the way for the exploration of a vast range of feeding strategies, environments, and ecological niches, allowing animals to become the dominant force in global ecosystems,” said Liu.

http://www.sciencedaily.com/  Science Daily

http://www.sciencedaily.com/releases/2014/08/140826205417.htm  Original web page at    Science Daily

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Evolutionary biology: Why cattle, pigs only have two toes

The fossil record shows that the first primitive even-toed ungulates had legs with five toes (=digits), just like modern mice and humans. During their evolution, the basic limb skeletal structure was significantly modified such that today’s hippopotami have four toes, while the second and fifth toe face backwards in pigs. During evolutionary diversification of vertebrate limbs, the number of toes in even-toed ungulates such as cattle and pigs was reduced and transformed into paired hooves. Scientists at the University of Basel have identified a gene regulatory switch that was key to evolutionary adaptation of limbs in ungulates. The study provides fascinating insights into the molecular history of evolution and is published by Nature today. The fossil record shows that the first primitive even-toed ungulates had legs with five toes (=digits), just like modern mice and humans. During their evolution, the basic limb skeletal structure was significantly modified such that today’s hippopotami have four toes, while the second and fifth toe face backwards in pigs. In cattle, the distal skeleton consists of two rudimentary dew claws and two symmetrical and elongated middle digits that form the cloven hoof, which provides good traction for walking and running on different terrains. A team led by Prof. Rolf Zeller from the Department of Biomedicine at the University of Basel has now investigated the molecular changes which could be responsible for the evolutionary adaptation of ungulate limbs. To this aim, they compared the activity of genes in mouse and cattle embryos which control the development of fingers and toes during embryonic development. The development of limbs in both species is initially strikingly similar and molecular differences only become apparent during hand and foot plate development: in mouse embryos the so-called Hox gene transcription factors are distributed asymmetrically in the limb buds which is crucial to the correct patterning of the distal skeleton. In contrast, their distribution becomes symmetrical from early stages onward in limb buds of cattle embryos: “We think this early loss of molecular asymmetry triggered the evolutionary changes that ultimately resulted in development of cloven-hoofed distal limb skeleton in cattle and other even-toed ungulates,” says Developmental Geneticist Prof. Rolf Zeller.

The scientists in the Department of Biomedicine then focused their attention on the Sonic Hedgehog (SHH) signaling pathway, as it controls Hox gene expression and the development of five fingers and toes in mice and humans. They discovered that the gene expression in limb buds of cattle embryos is altered, such that the cells giving rise to the distal skeleton fail to express the Hedgehog receptor, called Patched1. Normally, this receptor serves as an antenna for SHH, but without Patched1 the SHH signal cannot be received and the development of five distinct digits is disrupted. The researchers could establish that the altered genomic region — a so-called cis-regulatory module — is linked to the observed loss of Patched1 receptors and digit asymmetry in cattle embryos. “The identified genetic alterations affecting this regulatory switch offer unprecedented molecular insights into how the limbs of even-toed ungulates diverged from those of other mammals roughly 55 million years ago,” explains Rolf Zeller. At this stage, it is unclear what triggered inactivation of the Patched1 gene regulatory switch. “We assume that it is the result of progressive evolution, as this switch degenerated in cattle and other even-toed ungulates, while it remained fully functional in some vertebrates such as mice and humans.”

http://www.sciencedaily.com/  Science Daily

July 22, 2014

http://www.sciencedaily.com/releases/2014/06/140618131927.htm  Original web page at Science Daily

 

 

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A new toad from the ”warm valleys” of Peruvian Andes

A new species of toad was discovered hiding in the leaf litter of the Peruvian Yungas. The word is used widely by the locals to describe ecoregion of montane rainforests, and translates as “warm valley” in English. The new species Rhinella yunga was baptized after its habitat preference. The study was published in the open access journal ZooKeys. Like many other toads of the family Bufonidae the new species Rhinella yunga has a cryptic body coloration resembling the decaying leaves in the forest floor (“dead-leaf pattern”), which is in combination with expanded cranial crests and bony protrusions cleverly securing perfect camouflage. The different colors and shapes within the same species group however make the traditional morphological methods of taxonomic research hard to use to identify the real species diversity within the family. Nevertheless, Rhinella yunga is distinct from all related species in absence of a tympanic membrane, a round membranous part of hearing organ being normally visible on both sides of a toad’s head. “It appears that large number of still unnamed cryptic species remains hidden under some nominal species of the Rhinella margaritifera species group,” explains Dr Jiří Moravec, National Museum Prague, Czech Republic.

Among the other interesting characteristics of the true toads from the family Bufonidae are a typical warty, robust body and a pair of large poison excreting parotid glands on the back of their heads. The poison is excreted by the toads when stressed as a protective mechanism. Some toads, like the cane toad Rhinella marina, are more toxic than others. Male toads also possess a special organ, which after removing of testes becomes an active ovary and the toad, in effect, becomes female.

http://www.sciencedaily.com/  Science Daily February 4, 2014

http://www.sciencedaily.com/releases/2014/01/140117104033.htm  Original web page at Science Daily