Ancient retroviruses played a key role in the evolution of vertebrate brains

Researchers report February 15 in the journal Cell that ancient viruses may be to thank for myelin -- and, by extension, our large, complex brains. The team found that a retrovirus-derived genetic element or "retrotransposon" is essential for myelin production in mammals, amphibians, and fish. The gene sequence, which they dubbed "RetroMyelin," is likely a result of ancient viral infection, and comparisons of RetroMyelin in mammals, amphibians, and fish suggest that retroviral infection and genome-invasion events occurred separately in each of these groups.

"Retroviruses were required for vertebrate evolution to take off," says senior author and neuroscientist Robin Franklin of Altos Labs-Cambridge Institute of Science.

"If we didn't have retroviruses sticking their sequences into the vertebrate genome, then myelination wouldn't have happened, and without myelination, the whole diversity of vertebrates as we know it would never have happened."

Myelin is a complex, fatty tissue that ensheathes vertebrate nerve axons.

It enables rapid impulse conduction without needing to increase axonal diameter, which means nerves can be packed closer together.

It also provides metabolic support to nerves, which means nerves can be longer.

Myelin first appeared in the tree of life around the same time as jaws, and its importance in vertebrate evolution has long been recognized, but until now, it was unclear what molecular mechanisms triggered its appearance.

The researchers noticed RetroMyelin's role in myelin production when they were examining the gene networks utilized by oligodendrocytes, the cells that produce myelin in the central nervous system.

Specifically, the team was investigating the role of noncoding regions including retrotransposons in these gene networks -- something that hasn't previously been explored in the context of myelin biology.

"Retrotransposons compose about 40% of our genomes, but nothing is known about how they might have helped animals acquire specific characteristics during evolution," says first author Tanay Ghosh, a computational biologist at Altos Labs-Cambridge Institute of Science.

"Our motivation was to know how these molecules are helping evolutionary processes, specifically in the context of myelination."

In rodents, the researchers found that the RNA transcript of RetroMyelin regulates the expression of myelin basic protein, one of the key components of myelin.

When they experimentally inhibited RetroMyelin in oligodendrocytes and oligodendrocyte progenitor cells (the stem cells from which oligodendrocytes are derived), the cells could no longer produce myelin basic protein.

To examine whether RetroMyelin is present in other vertebrate species, the team searched for similar sequences within the genomes of jawed vertebrates, jawless vertebrates, and several invertebrate species.

They identified analogous sequences in all other classes of jawed vertebrates (birds, fish, reptiles, and amphibians) but did not find a similar sequence in jawless vertebrates or invertebrates.

"There's been an evolutionary drive to make impulse conduction of our axons quicker because having quicker impulse conduction means you can catch things or flee from things more rapidly," says Franklin.

Next, the researchers wanted to know whether RetroMyelin was incorporated once into the ancestor of all jawed vertebrates or whether there were separate retroviral invasions in the different branches.

To answer these questions, they constructed a phylogenetic tree from 22 jawed vertebrate species and compared their RetroMyelin sequences.

The analysis revealed that RetroMyelin sequences were more similar within than between species, which suggests that RetroMyelin was acquired multiple times through the process of convergent evolution.

The team also showed that RetroMyelin plays a functional role in myelination in fish and amphibians.

When they experimentally disrupted the RetroMyelin gene sequence in the fertilized eggs of zebrafish and frogs, they found that the developing fish and tadpoles produced significantly less myelin than usual.

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New geosciences study shows Triassic fossils that reveal origins of living amphibians

The smallest of newly found fossils can upend what paleontologists know about our history.

A team of paleontologists from Virginia Tech and the U.S. Petrified Forest National Park, among others, have discovered the first "unmistakable" Triassic-era caecilian fossil -- the oldest-known caecilian fossils -- thus extending the record of this small, burrowing animal by roughly 35 million years. The find also fills a gap of at least 87 million years in the known historical fossil record of the amphibian-like creature.

The fossil was first co-discovered by Ben Kligman, a doctoral student in the Department of Geosciences, part of the Virginia Tech College of Science, at Arizona's Petrified Forest National Park during a dig in 2019. Named by Kligman as Funcusvermis gilmorei, the fossil extends the history of caecilians 35 million years back to Triassic Period, roughly 250 million to 200 million years ago.

Prior to this new study, published today in the journal Nature, only 10 fossil caecilian occurrences were known, dating back to the Early Jurassic Period, about 183 million years ago. However, previous DNA studies estimated evolutionary origins of caecilians back to the Carboniferous or Permian eras, some 370 million to 270 million years ago, according to Kligman, marking that 87-million-year gap. However, no such fossils had been found.

"The discovery of the oldest caecilian fossils highlights the crucial nature of new fossil evidence. Many of the biggest outstanding questions in paleontology and evolution cannot be resolved without fossils like this," said Kligman, who previously discovered a 220-million-year-old species of cynodont or stem-mammal, a precursor of modern-day mammals. "Fossil caecilians are extraordinarily rare, and they are found accidentally when paleontologists are searching for the fossils of other more common animals. Our discovery of one was totally unexpected, and it transformed the trajectory of my scientific interests."

The discovery of the fossils was made in 2019 by Kligman and Petrified Forest National Park student intern Xavier Jenkins, now a Ph.D. student at Idaho State University, while the duo was processing fossiliferous sediment from the park's nicknamed Thunderstorm Ridge via a microscope. Funcusvermis was found in a layer of the Chinle Formation dated to approximately 220 million years ago, when Arizona was positioned near the equator at the central part of the supercontinent Pangaea, Kligman said. This region at the time was subject to a hot, humid climate. Today, Arizona is still hot, but has low humidity.

"Seeing the first jaw under the microscope, with its distinctive double row of teeth, sent chills down my back," Kligman said. "We immediately knew it was a caecilian, the oldest caecilian fossil ever found, and a once-in-a-lifetime discovery."

Previous to this find, the 87-million-year gap in the fossil record hid the early evolutionary history of caecilians, leading to a decades-long debate amongst scientists over the relationships of caecilians to their amphibian relatives, frogs and salamanders.

"Funcusvermis extends the humid equatorial pattern of occurrence seen in all known fossil and living caecilians, suggesting that the biogeographic history of caecilians has been guided by restriction to these ecological settings, likely due to physiological constraints linked to humidity, and constrained by the drift of continental plates into and out of the humid-equatorial zone after the fragmentation of Pangaea," Kligman said.

Modern caecilians are limbless amphibians with cylindrical bodies with a compact, bullet-shaped skull that helps them burrow underground. Now exclusively home to South and Central America, Africa, and southern Asia, caecilians spend their lives burrowing in leaf-litter or soil searching for prey such as worms and insects. This underground existence has made studying caecilians difficult for scientists. Kligman, tongue in cheek, describes modern caecilians as an "eyeless sock puppet with the body of a worm."

Funcusvermis actually shares skeletal features related more with early frog and salamander fossils, strengthening evidence for a shared origin and close evolutionary relationship between caecilians and these two groups. Funcusvermis also shares skeletal features with an ancient group of amphibians known to paleontologists as dissorophoid temnospondyls. Kligman adds, "Unlike living caecilians, Funcusvermis lacks many adaptations associated with burrowing underground, indicating a slower acquisition of features associated with an underground lifestyle in the early stages of caecilian evolution."

Name that tune

Now, here's the fun part: The genus name 'Funcusvermis' was inspired by the Ohio Players' 1972 song "Funky Worm" from their album Pleasure, a favorite song of the authors that was often played while excavating fossils at Thunderstorm Ridge. 'Funcus' is derived from the Latinized form of the English word Funky for the upbeat, rhythmic form of dance music, while 'vermis' is derived from the Latin word for worm. (It's an excellent song, by the way. Instant earworm, so to speak.)

The species name, gilmorei, honors Ned Gilmore, the collections manager at the Academy of Natural Sciences of Philadelphia's Drexel University. (Kligman is from Philadelphia and volunteered with Gilmore's herpetology wet collection as an undergraduate student. "He was an important mentor who helped inspire my interest in fossils and amphibians," Kligman said.)

Co-authors on the study include Michelle Stocker, an assistant professor, and Sterling Nesbitt, an associate professor, in the Virginia Tech Department of Geosciences and members of the Global Change Center that is part of the Fralin Life Sciences Institute. Other authors include Adam Marsh, lead paleontologist; Matthew Smith, museum curator; and William Parker, chief of science and resource management, all at the Petrified Forest National Park; and Bryan Gee, postdoctoral fellow at the University of Washington's Burke Museum and Department of Biology.

"As the eponymous song says, it's the funkiest worm in the world," Marsh quipped.

Stocker added, "What we collect really determines what we can say about which animals that were present, how many of them there were, and what they looked like. Without using these methods for fossil collection and analysis we would be missing out on knowing so many important aspects of this Triassic ecosystem. Now that we have a search image of what bones to look for and how to look for them, it will be exciting to see what other fossil localities preserve these early lissamphibians."

Nesbitt said finds such as this can reset the game board on paleontology, in the best sense of the phrase. "This find clearly demonstrates that some fossils that you can barely see can greatly change our understanding of entire groups that you can see today," he said.

What's happened since 2019

At the Petrified Forest National Park, where the initial discovery was found in 2019, the lower jaws of at least 70 individuals of Funcusvermis have been recovered as of summer 2022, making the area "the most abundant fossil caecilian-producing bonebed ever discovered," Kligman said.

Only a handful of bones of Funcusvermis have been found, including upper and lower jaws, a vertebra, and part of a hind-limb, Kligman said. All of the found bones were disarticulated, not as complete skeletons. Without complete skeletons, Kligman and his fellow researchers cannot exactly determine the body length of Funcusvermis, but inferences from isolated elements, such as the lower jaw being less than a quarter of an inch long, indicate that Funcusvermis was a tiny animal.

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Solid salamander: Prehistoric amphibian was as heavy as a pygmy hippo

The last of the temnospondyls -- amphibians that look more like crocodiles -- became extinct during the Cretaceous period, about 120 million years ago, after thriving on Earth for more than 200 million years.

Now a team of scientists led by Lachlan Hart, a palaeontologist and PhD candidate in the School of Biological, Earth & Environmental Sciences at UNSW Sydney, has assessed various methods of estimating the weight of these unique extinct animals. The team's study is published in Palaeontology.

"Estimating mass in extinct animals presents a challenge, because we can't just weigh them like we could with a living thing," said Mr Hart. "We only have the fossils to tell us what an animal looked like, so we often need to look at living animals to get an idea about soft tissues, such as fat and skin."

Temnospondyls as case studies

Mr Hart said temnospondyls were "very strange animals."

"Some grew to enormous sizes, six or seven metres long. They went through a larval (tadpole) stage just like living amphibians. Some had very broad and round heads -- such as Australia's Koolasuchus, recently named as the Victorian State Fossil Emblem -- and others, like the temnospondyls we used in this study, had heads that were more croc-like."

The 1.8 metre-long Eryops megacephalus lived during the Permian period in what is now the USA, while the slightly longer Paracyclotosaurus davidi is known from the Triassic of Australia. The more aquatically inclined Paracyclotosaurus was the heftier of the two, tipping the scales at roughly 260 kilograms, where Eryops was a more modest 160 kilograms.

"The size of an animal is important for many aspects of their life," said Mr Hart. "It impacts what they feed on, how they move and even how they handle cold temperatures. So naturally, palaeontologists are interested in calculating the body mass of extinct creatures so we can learn more about how they lived.

"There have been several studies on body mass estimation in other groups of extinct animals, such as dinosaurs, but not extensively on temnospondyls.

"They survived two of Earth's Big Five mass extinction events which makes them a very interesting case study on how animals adapted following these global catastrophes," Mr Hart said.

Because temnospondyls have no direct living relatives, the team of scientists had to assemble a selection of five modern 'analogues' (such as the Chinese Giant Salamander and the Saltwater Crocodile) to test a total of 19 different body mass estimation techniques to determine their suitability for use in temnospondyls.

"We found several methods which gave us consistently accurate body mass estimations in our five living animals, which included using mathematical equations and 3-dimensional digital models of the animals," said Dr Nicolas Campione from the University of New England, Armidale, an authority on body mass estimation who was also involved in the study. "We hypothesised that as these methods are accurate for animals which lived and looked like temnospondyls, they would also be appropriate for use with temnospondyls."

Dr Matthew McCurry, Senior Lecturer in Earth Science at UNSW, and co-author on the study said, "This work has shown there are multiple methods for estimating mass in temnospondyls.

Read more at Science Daily

Vocal communication originated over 400 million years ago

The use of vocalizations as a resource for communication is common among several groups of vertebrates: singing birds, croacking frogs, or barking dogs are some well-known examples. These vocalizations play a fundamental role in parental care, mate attraction and various other behaviors. Despite its importance, little is known about when and at what stage in the evolutionary history of vertebrates this behavior first appeared. Comparative analyses can provide insights into the evolutionary origin of acoustic communication, but they are often plagued by missing information from key groups that have not been broadly studied.

Acoustic abilities are widespread in land vertebrates

An international research team led by the University of Zurich (UZH) has therefore focused on species that have never been accessed before. Their study includes evidence for 53 species of four major clades of land vertebrates -- turtles, tuataras, caecilians and lungfishes -- in the form of vocal recordings and contextual behavioral information accompanying sound production. "This, along with a broad literature-based dataset including 1800 different species covering the entire spectrum shows that vocal communication is not only widespread in land vertebrates, but also evidence acoustic abilities in several groups previously considered non-vocal," says first author Gabriel Jorgewich-Cohen, PhD student at the Paleontological Institute and Museum of UZH. Many turtles, for example, which were thought to be mute are in fact showing broad and complex acoustic repertoires.

Last common ancestor lived about 407 million years ago

To investigate the evolutionary origins of acoustic communication in vertebrates, the researchers combined relevant data on the vocalization abilities of species like lizards, snakes, salamanders, amphibians, and dipnoi with phylogenetic trait reconstruction methods. Combined with data of well-known acoustic clades like mammals, birds, and frogs, the researchers were able to map vocal communication in the vertebrate tree of life. "We were able to reconstruct acoustic communication as a shared trait among these animals, which is at least as old as their last common ancestor that lived approximately 407 million years before present," explains Marcelo Sánchez, who led the study.

Read more at Science Daily

Beavers may help amphibians threatened by climate change

 The recovery of beavers may have beneficial consequences for amphibians because beaver dams can create the unique habitats that amphibians need.

That finding was reported by four WSU Vancouver scientists in a paper published in the journal Freshwater Biology. The research took place in the Gifford Pinchot National Forest of the Cascade Range, where the researchers identified 49 study sites either with or without beaver dams. The researchers found the beaver-dammed sites were 2.7 times higher in amphibian species richness than the undammed sites.

Certain types of amphibians, particularly those that develop more slowly, such as red-legged frogs and northwestern salamanders, were detected almost exclusively in dammed sites.

"Beaver-dammed wetlands support more of the amphibian species that need a long time to develop in water as larvae before they are able to live on land as adults," said Jonah Piovia-Scott, assistant professor in the School of Biological Sciences and one of the authors of the article.

Beavers, once abundant in the Pacific Northwest, were hunted nearly to extinction in the 19th century. But, in an effort to improve wildlife habitat and mitigate the effects of climate extremes, some land managers are relocating beavers into places they occupied in the past, and beavers' numbers are slowly recovering, which is also benefiting amphibians, according to the study.

Red-legged frogs and northwestern salamanders are also the species most threatened by climate change, which is projected to bring drier summer conditions to streams and wetlands in the Cascade Range. By expanding existing ponds and increasing the time before they dry up, beaver dams are allowing such species more time to reproduce and develop.

"Beavers may be a key component of ecological resilience to climate change in these ecosystems," Piovia-Scott said.

In addition to Piovia-Scott, the authors of the study are Kevan Moffett, assistant professor in the School of the Environment; John Romansic, former postdoctoral scholar in the School of Biological Sciences; and Nicolette Nelson, former graduate student in the School of Biological Sciences.

From Science Daily

First evidence of snake-like venom glands found in amphibians

Caecilians are limbless amphibians that, to the untrained eye, can be easily mistaken for snakes. Though caecilians are only distantly related to their reptilian cousins, researchers in a study appearing July 3 in the journal iScience describe specialized glands found along the teeth of the ringed caecilian (Siphonops annulatus), which have the same biological origin and possibly similar function to the venom glands of snakes. If further research can confirm that the glands contain venom, caecilians may represent the oldest land-dwelling vertebrate animal with oral venom glands.

Caecilians are peculiar creatures, being nearly blind and using a combination of facial tentacles and slime to navigate their underground tunnels. "These animals produce two types of secretions -- one is found mostly in the tail that is poisonous, while the head produces a mucus to help with crawling through the earth," says senior author Carlos Jared, a biologist and Director of the Structural Biology Lab at the Butantan Institute in São Paulo. "Because caecilians are one of the least-studied vertebrates, their biology is a black box full of surprises."

"It is while examining the mucous glands of the ringed caecilian that I stumbled upon a never before described set of glands closer to the teeth," says first author Pedro Luiz Mailho-Fontana, a post-doctoral student in the Structural Biology Lab at the Butantan Institute.

What Mailho-Fontana found were a series of small fluid-filled glands in the upper and lower jaw, with long ducts that opened at the base of each tooth. Using embryonic analysis, he found that these oral glands originated from a different tissue than the slime and poison glands found in the caecilian's skin. "The poisonous skin glands of the ringed caecilian form from the epidermis, but these oral glands develop from the dental tissue, and this is the same developmental origin we find in the venom glands of reptiles," says Mailho-Fontana. This marks the first time glands of this kind have been found in an amphibian.

Researchers suspect that the ringed caecilian may use the secretions from these snake-like oral glands to incapacitate its prey. "Since caecilians have no arms or legs, the mouth is the only tool they have to hunt," says co-author Marta Maria Antoniazzi, an evolutionary biologist at the Butantan Institute. "We believe they activate their oral glands the moment they bite down, and specialized biomolecules are incorporated into their secretions.

A preliminary chemical analysis of the oral gland secretions of the ringed caecilian found high activity of phospholipase A2, a common protein found in the toxins of venomous animals. "The phospholipase A2 protein is uncommon in non-venomous species, but we do find it in the venom of bees, wasps, and many kinds of reptiles," says Mailho-Fontana. In fact, the biological activity of phospholipase A2 found in the ringed caecilian was higher than what is found in some rattlesnakes. Still, more biochemical analysis is needed to confirm whether the glandular secretions are toxic.

If future work can verify the secretions are toxic, caecilian oral glands could indicate an early evolutionary design of oral venom organs. "Unlike snakes which have few glands with a large bank of venom, the ringed caecilian has many small glands with minor amounts of fluid. Perhaps caecilians represent a more primitive form of venom gland evolution. Snakes appeared in the Cretaceous probably 100 million years ago, but caecilians are far older, being roughly 250 million years old," Jared says.

Read more at Science Daily

Giant Chinese salamander is at least five distinct species, all heading toward extinction

This photograph shows one living Chinese giant salamander from Guangxi Province.

With individuals weighing in at more than 140 pounds, the critically endangered Chinese giant salamander is well known as the world's largest amphibian. But researchers reporting in the journal Current Biology on May 21 now find that those giant salamanders aren't one species, but five, and possibly as many as eight. The bad news as highlighted by another report appearing in the same issue is that all of the salamanders -- once thought to occur widely across China -- now face the imminent threat of extinction in the wild, due in no small part to demand for the amphibians as luxury food.

The discoveries highlight the importance of genetic assessments to properly identify the salamanders, the researchers say. It also suggests that the farming and release of giant salamanders back into the wild without any regard for their genetic differences is putting the salamanders' already dire future at even greater risk. In fact, some of the five newly identified species may already be extinct in the wild.

"We were not surprised to discover more than one species, as an earlier study suggested, but the extent of diversity -- perhaps up to eight species -- uncovered by the analyses sat us back in our chairs," says Jing Che from the Kunming Institute of Zoology, Chinese Academy of Sciences. "This was not expected."

"The overexploitation of these incredible animals for human consumption has had a catastrophic effect on their numbers in the wild over an amazingly short time span," adds Samuel Turvey, from ZSL (Zoological Society of London. "Unless coordinated conservation measures are put in place as a matter of urgency, the future of the world's largest amphibian is in serious jeopardy."

The researchers were surprised to learn just how much movement of salamanders has already occurred due to human intervention. Salamander farms have sought to "maximize variation" by exchanging salamanders from distant areas, without realizing they are in fact distinct species, Che explains. As a result, she says, wild populations may now be at risk of becoming locally maladapted due to hybridization across species boundaries.

The researchers including Ya-Ping Zhang and Robert Murphy suspected Chinese giant salamanders might represent distinct species despite their similar appearances. That's because the salamanders inhabit three primary rivers in China, and several smaller ones, they explain. Each runs independently to sea.

Given that giant salamanders can't move across the land, they suspected that salamanders living in different river systems might have had opportunity to diverge over time into what should now be recognized as distinct species. And, indeed, that's exactly what the genetic evidence now suggests.

In the second study, Turvey and colleagues conducted field surveys and interviews from 2013 and 2016, in an effort that was possibly the largest wildlife survey ever conducted in China. The data revealed that populations of this once-widespread species are now critically depleted or extirpated across all surveyed areas of their range, and illegal poaching is widespread. The researchers were unable to confirm survival of wild salamanders at any survey site.

While the harvesting of wild salamanders is already prohibited, the findings show that farming practices and existing conservation activities that treat all salamander populations as a single species are potentially doing great damage, the researchers say.

"Conservation strategies for the Chinese giant salamander require urgent updating," Che says. She says it is especially critical to reconsider the design of reserves to protect the salamanders and an effort that has already released thousands of farm-started baby salamanders back into the wild.

Read more at Science Daily

Sea turtle crisis: Moisture, not just heat impacts sex of sea turtle hatchlings

A sea turtle hatchling emerges from an egg on a beach in Palm Beach County in southeast Florida. Since 2002, researchers have found that 97 to 100 percent of the hatchlings have been female.

Alarming results from a recent gender ratio study revealed that 99 percent of young green turtles from Australia's Northern Great Barrier Reef are female and that male sea turtles are disappearing. Closer to home, researchers from Florida Atlantic University have documented a similar trend in sea turtle hatchlings in southeast Florida. Since 2002, they have studied sea turtles in Palm Beach County and discovered that 97 to 100 percent of the hatchlings have been female.

Unlike humans, turtles and other reptiles like crocodiles who lay their eggs do not have sex chromosomes. In sea turtles, sex is determined by the nest's environment: warmer temperatures produce females and cooler temperatures produce males.

However, it is not just temperature that affects embryogenesis and the phenotype of the resulting hatchlings. Moisture changes the microclimate experienced by the eggs inside the nest and can significantly affect their development. Wetter substrates tend to produce more males and drier substrates tend to produce more females.

In a study published in Zoology, FAU researchers are the first to show why and how moisture conditions inside the nest affect the development and sex ratios of turtle embryos. They are the first to estimate sex ratios using a male-specific, transcriptional molecular marker Sox9, a marker of testis development in sea turtles and freshwater turtles.

The researchers found that the coolest and the wettest substrates produce 100 percent males compared to 42 percent males from the warmest and driest treatment. They also found that embryonic growth appears to be more sensitive to temperature at earlier stages of development and to moisture at later stages.

"During incubation, the turtle embryo grows inside the nest from a few cells to a fully formed and independent organism at hatching," said Jeanette Wyneken, Ph.D., author of the study and a professor of biological sciences in FAU's Charles E. Schmidt College of Science. "For proper development, embryos require an appropriate range of temperature, moisture, salinity, and respiratory gases."

Using their novel experimental design, Wyneken and study collaborators Sarah L. Milton, Ph.D., an associate professor of biological sciences at FAU, Itzel Sifuentes-Romero, Ph.D., a Fulbright postdoctoral fellow at FAU, and Boris M. Tezak, a Ph.D. candidate at FAU, found differences in developmental rates, egg mass and sex ratios. Results show that embryos developed slowly in cooler and wetter sand substrates while water uptake by the eggs was significantly greater on wetter substrates.

"We found that development differences were due to moisture interacting with temperature where increased water content of the sand resulted in temperatures that were 2 to 3 degrees Celsius lower than air temperatures," said Wyneken.

For the study, the researchers incubated eggs from the Trachemys scripta elegans, a semi-aquatic turtle, under different temperature and moisture regimes to study the effect of the two environmental factors on developmental rate, egg mass, embryo mass and length, and sex ratio. They monitored embryonic development until stage 22 when their sex is determined. Turtle embryonic development is divided into 27 stages. The pivotal temperature is the constant temperature (29 degrees Celsius or 84.2 degrees Fahrenheit) at which 50:50 sex ratio is expected. Sex ratio was based on expression levels of Sox9 and all data were tested for normality and for homogeneity before statistical analysis.

This laboratory study is consistent with field studies of freshwater turtles and sea turtles. Results of the study also are relevant when considering nesting phenology in the wild because conditions such as temperature and rainfall often vary depending across the nesting season.

"Our study demonstrates how moisture may change the incubation conditions inside nests by changing the temperature experienced by eggs, which affects development, growth and sex ratios," said Wyneken. "Furthermore, results of our study highlight the importance of including moisture conditions when predicting embryo growth and sex ratios and in developing proxies of embryonic development. Improving accuracy is particularly important when trying to assess the impact of climate change in species with temperature-dependent sex determination and other forms of environmental determination."

Read more at Science Daily

Ancient amphibian had mouthful of teeth ready to grab you

A thematic diagram showing a cut across the skull showing the position of the denticulate plates that covered the soft palate. On the left is at resting stage, on the right, ventral movement of the soft palate by retraction of the eyeballs, during feeding

The idea of being bitten by a nearly toothless modern frog or salamander sounds laughable, but their ancient ancestors had a full array of teeth, large fangs and thousands of tiny hook-like structures called denticles on the roofs of their mouths that would snare prey, according to new research by paleontologists at the University of Toronto Mississauga (UTM).

In research published online in a recent issue of PeerJ, an open access journal, Professor Robert Reisz, Distinguished Professor of Paleontology at UTM, explains that the presence of such an extensive field of teeth provides clues to how the intriguing feeding mechanism seen in modern amphibians was also likely used by their ancient ancestors.

They believe that the tooth-bearing plates "were ideally suited for holding on to prey, such as insects or smaller tetrapods, may have facilitated a method of swallowing prey items via retraction of the eyeballs into the mouth, as some amphibians do today.

In many vertebrates, ranging from fish to early synapsids (ancestors of mammals), denticles are commonly found in dense concentrations on the bones of the hard palate (roof of the mouth). However, in one group of tetrapods, temnospondyls (which are thought to be the ancestors of modern amphibians) these denticles were also found on small, bony plates that filled the large soft part of the palate. The entire roof of the mouth was covered with literally thousands of these tiny teeth that they used to grab prey. Since these toothy plates were suspended in soft tissue, they are often lost or scattered during fossilization.

Denticles are significantly smaller than the teeth around the margin of the mouth -- on the order of dozens to a couple hundred microns in length. They are actually true teeth, rather than just protrusions in the mouths of these tetrapods, says Reisz and his colleagues, Bryan Gee and Yara Haridy, both graduate students in paleontology.

"Denticles have all of the features of the large teeth that are found on the margin of the mouth," says Reisz. "In examining tetrapod specimens dating back ~289 million years, we discovered that the denticles display essentially all of the main features that are considered to define teeth, including enamel and dentine, pulp cavity and peridontia."

In reaching these conclusions, the researchers analyzed specimens unearthed from the fossil-rich Dolese Brothers Limestone Quarry near Richards Spur, Oklahoma. They were extraordinarily well preserved, making them ideal candidates for study.

The researchers extracted and isolated the denticle-bearing plates, created thin section slides and examined them under the microscope -- no small feat since denticles on this animal were only about 100 microns long.

Read more at Science Daily

Deadly Snake Lures Frogs With Its Forked Tongue

Africa's deadly puff adder is a serious ambush predator, with fierce fangs and powerful venom. However, it turns out the striking reptile has another weapon. Its tongue is a forked instrument of deception, if you're a frog.

That was the discovery made by a pair of University of the Witwatersrand (Wits) researchers, who recorded and then pored over thousands of hours of video of puff adders hunting. The footage revealed a bit of trickery the snakes were using to draw frogs closer to them – just close enough to strike and snare the poor amphibians.

In a process called "lingual luring," the snakes were essentially fooling frogs into thinking their tongues were something the frog would like to eat - a tasty invertebrate such as a worm. Curious, and hungry, the frogs hopped too close, and then it was too late for them to beat a retreat.

"We know that snakes use their tongues to pick up scent cues in their environment," explained Wits researcher Xavier Glaudas, in a statement. "But these snakes were extending their tongues out of their mouths for up to 30 seconds, which is dramatically longer to what they do when they are just using their tongues to 'smell' their environment."

Although other animals – some wading birds, aquatic snakes and alligator snapping turtles – use tongue luring, "this is the first time that it is reported in a terrestrial snake," Glaudas said.

What's more, only frogs got the lingual luring treatment. Glaudas and research partner Graham Alexander never caught the snakes using the hunting maneuver on other kinds of prey, such as small mammals. That told the scientists that the snakes were making foraging decisions based on the type of potential food within view, which indicated that snakes might have more going on upstairs than typically thought.

"Our study reveals the diverse predatory strategies and complex decision-making process used by 'sit-and-wait' predators, such as ambush-foraging snakes, to catch prey, and indicates that snakes may have higher cognitive abilities than those usually afforded to them," Glaudas and Alexander wrote, in a paper on their findings published in the journal Behavioral Ecology and Social Biology.

Read more at Discovery News

Philippines Island of Mindanao a Biodiversity Hot Spot

The Caraga region of northeast Mindanao, an island in the southern Philippines, has been identified as the top biodiversity hot spot for amphibians and reptiles in the country, the region boasting more species, for an area of its size, than any other in the Philippines.

That's according to researchers who have just documented 126 species in the area — including an array of frogs, snakes, lizards, turtles and crocodiles — in a new study in the online journal ZooKeys.

The island, with a history of environment loss, thanks largely to illegal logging in the timber-rich location, made for a challenging study subject, in terms of species location and documentation.

"Mindanao is a place where, unfortunately, the original forest cover was more than 85 percent, but now it's down to 6 percent original forest, and 15 percent is second-growth vegetation," said study co-author Rafe Brown, University of Kansas curator-in-charge of herpetology, in a statement.

"Mindanao has extensive mineral resources and forests with valuable timber," Brown explained. "Tropical rainforest soils are also very fertile, making the lowlands attractive to agribusiness. There's been conflict over those resources for hundreds of years."

Nonetheless, Brown and his colleagues forged on. Their efforts to explore the region paid off, to the tune of cataloging 49 lizards, 40 frogs, 35 snakes, a crocodile and a freshwater turtle.

And what efforts. It's one thing to ponder the number of species and another to actually have to go find them.

"We typically dig around tree trunks looking for animals that live underground," Brown said. "We search rivers and streams, turning over rocks, splitting open decaying logs looking for lizards or frogs. We climb trees, looking for tree-dwelling lizards, or place pitfall traps in the ground to catch lizards and small snakes that live in the leaf litter. We also use sticky traps like people use to catch pests in homes."

Here are a few of the critters Brown and his colleagues documented:

A white-lined water snake (Rhabdophis auriculata auriculata):

A frilled tree frog (Kurixalus appendiculatus):

And this cool, two-spotted flying lizard (Draco bimaculatus):

"The biodiversity is so high in this one pocket of northeast Mindanao, largely because the ranges of so many species in the archipelago overlap in this one area," said Brown. "We knew it was really diverse, but we didn't have a sense of this one area being the bull's-eye, the epicenter of this diversity."

Read more at Discovery News