Monday 29 June 2020

Illusionist Frog Attracts Mates Without Unwanted Attention From Predators - The simultaneous mating calls of the male pug-nosed tree frog confuses bats but not female frogs – via Herp Digest

By Alex Fox 
MAY 7, 2020
Male tungara frogs of Central and South America call out to potential mates with reckless abandon. During the rainy season, they wait for pockets of relative silence amid the cacophony of the rainforest and belt out a song that could attract females’ attention or get them eaten by an eavesdropping bat. Even worse, their most seductive calls are also more likely to turn them into someone’s dinner.
It might seem like a rough trade off, but trying to stand out from the acoustic lineup is typical among frogs, explains Ximena Bernal, an ecologist at Purdue University and researcher at the Smithsonian Tropical Research Institute in Panama.
In the rainforest’s dry season, another frog species has a more confusing way of flirting. When it’s time for male pug-nosed tree frogs to turn on the charm, they all call out at the same time.
“Synchronizing calls is like talking over other people which, as we all know, reduces our ability to understand what the person is saying,” says Bernal via email. Calling out at the same time seemed like a confusing strategy for pug-nosed frogs to get dates, but the tungara’s sometimes fatal bids for attention gave Bernal and her colleagues a clue.
After studying the pug-nosed frogs in the rainforests of Panama and in the lab, the researchers have found that the near-perfect synchrony of the frogs’ mating calls confuses their would-be predators—all while remaining plenty alluring to females, reports Pratik Pawa for Science News.
When one pug-nosed tree frog (Smilisca sila) trumpets his love song, other nearby males start their calls almost instantly. With all the frogs calling out at once, bats and most other vertebrates think the sound is all coming from the frog that started the chorus.
“Humans experience this illusion too, it’s called the ‘Precedence Effect’. When we hear two short sounds in quick succession, we think the sound is only coming from the location of the first sound,” says Bernal, who is also affiliated with Purdue University in Indiana, in a statement.
This auditory illusion obscures the locations of all the frogs who joined in late and protects them from predators, the researchers report in the journal American Naturalist.
This places the poor saps leading the call at a big disadvantage, which drives each frog to hold its note as long as possible—resulting in gulfs of silence between the bouts of song, Bernal tells Science News.
But what do the female frogs think? Surprisingly, the team’s experiments suggest females don’t show any preference for the bold males who initiated the calls. What remains a mystery is how the females avoid falling prey to their species’ own illusory tactics and remain capable of choosing their mate. 
This phenomenon is something Bernal hopes to explore in future research. “Is there something specific about their hearing mechanisms that allows them to detect and accurately locate two signals even though they are produced milliseconds apart?” she wonders.Synchronous calls aren’t this illusionist amphibian’s only tactics for evading predators. Males are known to prefer to sing near waterfalls. This placement isn’t just for ambiance; the sound of the rushing water overlaps with the frequency of the males’ calls and helps obscure them to hungry bats.
Prior research has also shown they vary their calls in accordance with the moon. Males are more vocal on nights when moonlight is brighter and they can more easily spot marauding bats, and quieter when it’s darker.
Bernal speculates that the pug-nosed frog’s choice of mating season may account for its multiple strategies for avoiding predators: “This is the main species calling in the dry season so it may be that it is under strong selection from many frog-eating beasts.”

New study reveals how metamorphosis has shaped the evolution of salamanders

JUNE 23, 2020
A team of scientists, led by Natural History Museum postdoctoral researcher Dr. Anne-Claire Fabre, have conducted the first study on how metamorphosis has influenced the evolution of salamanders.
Using micro-CT scanning to study the skulls of this group of animals, the team were able to build a huge dataset of 148 species of salamanders and used cutting-edge methods to describe the shape of the skull with nearly 1000 reference points, known as landmarks.
Dr. Fabre said, "Most studies of this kind are limited to just a few dozen landmarks. Our study is the first large-scale investigation of this incredibly diverse group. We have captured the shape of the skull in such great detail that it has allowed us to learn more than ever before about how these creatures evolved."
The results showed that the ancestor of all salamanders was metamorphic but that different life cycles have evolved at least 11 times across the group. Even more interesting, when different life cycles evolve, salamanders show a burst of rapid evolution, showing that shifts in life cycle promoted the evolution of new forms and increased their diversity.
Prof. Anjali Goswami, a research leader at the Natural History Museum, who is the senior author of the study, said, "We can see that metamorphosis has profoundly influenced salamander evolution, allowing for more independent evolution of the parts of the skull related to feeding and ultimately resulting in a greater diversity of skull shapes. This means that metamorphosis, and repeated changes from metamorphosis to other life cycles like live birth or losing the larval or adult stage entirely, have been key drivers of the diversity of salamanders over the past 180 million years."


Global turtle study highlights extinction risk and roadmap to recovery

JUNE 23, 2020

A Western Sydney University researcher has contributed to the first global and comprehensive assessment of the world's turtle and tortoise species. The study found half of all 360 turtle and tortoise species worldwide face imminent extinction, but action undertaken now could reverse the decline and save many species.
Published today in Current Biology, 51 experts with the International Union for Conservation of Nature's (IUCN) Tortoise and Freshwater Turtle Specialist Group, are calling for the end of the trade of wild turtles for food and pets as key to a global conservation strategy.
Hundreds of thousands of turtles and tortoises are collected for the wildlife trade every year. Turtles and tortoises are long-living and slow-growing species, which means they can't reproduce fast enough to replenish populations that are taken from the wild. Three species of turtles and tortoises have gone extinct in the last two centuries, but that number will climb if the trade isn't curbed.
Co-author, Associate Professor Ricky Spencer from the School of Science at Western Sydney University, said Australia is not immune to the impacts of turtle trading, and attacks from invasive predators, road mortality, habitat destruction and drought, are all factors contributing to the decline of Australia's most common turtle species by up to 91 per cent.
"In Australia, we are seeing no signs of turtles in some areas, where we previously recorded them in huge numbers. Foxes are the main persistent source of predation, with growing urbanisation, poor water quality and habitation destruction compounding the issues turtles face," explained Associate Professor Spencer.
"The exotic pet trade and illegal smuggling of wildlife both in and out of Australia is also a contributing factor. It is big business."
The study reinforces the essential roles turtles play in the world's ecosystems. They provide critical services such as energy flow, nutrient recycling, scavenging, soil dynamics and seed dispersal in the terrestrial, freshwater, and marine ecosystems in which they occur.
"The research we are conducting at the Experimental Wetland Facility on the University's Hawkesbury campus shows that without turtles in our rivers, water quality would reach toxic levels during our hot summers. During the recent fish kills in the Murray-Darling River system, turtles were likely instrumental in cleaning up the river," said Associate Professor Spencer.
The researchers recommend captive breeding and head starting programs as ways to help certain species of turtles and tortoises. But to be effective, there must be natural habitat remaining to release the animals into. Species like the Australian western swamp turtle were rescued from near extinction by captive breeding efforts, but it is difficult to breed some species in captivity.

In the wild, chimpanzees are more motivated to cooperate than bonobos

JUNE 24, 2020

We humans have unique cooperative systems allowing us to cooperate in large numbers. Furthermore, we provide help to others, even outside the family unit. How we developed these cooperative abilities and helping behavior during our evolutionary past remains highly debated. According to one prominent theory, the interdependence hypothesis, the cognitive skills underlying unique human cooperative abilities evolved when several individuals needed to coordinate their actions to achieve a common goal, for example when hunting large prey or during conflict with other groups. This hypothesis also predicts that humans who rely more on each other to achieve such goals, will be more likely to provide help and support to one another in other situations.
"While we cannot study the behavior of our human ancestors," explains Roman Wittig, a senior author and head of the Taï Chimpanzee Project, "we can learn how relying on others may influence helping behavior in our ancestors by studying our closest living relatives, chimpanzees and bonobos." Chimpanzees are more territorial than bonobos and in some populations engage more frequently in group hunts. According to the interdependence hypothesis, chimpanzees should thus have evolved a higher tendency to cooperate and help others in the group.
To test this hypothesis, researchers from the Max Planck Institute for Evolutionary Anthropology, Harvard University and Liverpool John Moores University, presented 82 chimpanzees and bonobos from five different communities with a model of a Gaboon viper, a deadly snake. During the experiment the apes could cooperate with each other by producing alarm calls to inform conspecifics about the snake. This represents the first experimental study ever conducted in wild bonobos. "This experimental study is a novel and promising approach to probe bonobo's mind," says Gottfried Hohmann, a senior author on the study and head of the LuiKotale bonobo project. Martin Surbeck, co-author on the paper adds: "This study should stimulate several more experimental studies on wild bonobo cooperation, cognition, and communication."

Sunday 28 June 2020

Eat Rat, Make New Body: Easy Stuff for Pythons - The extreme metabolism of some snakes could provide leads on how to regenerate human tissue. via Herp Digest

By Carl Zimmer, Photographs by Wes Frazer, New York Times, 5/12/15
 TUSCALOOSA, Ala. — On a cold, gray winter day, Stephen Secor drove to the outskirts of town to catch up with some old friends. He pulled into the driveway of David and Amber Nelson, who welcomed him into their converted basement, filled with stacks of refrigerator-size, glass-doored cages. Each cage contained a massive snake. Some of the Nelsons’ pythons and boa constrictors were recent adoptions from Dr. Secor’s lab, a few miles to the west at the University of Alabama.
 Dr. Secor and Mr. Nelson, a product manager at a local car parts factory, hoisted the snakes one at a time out of their cages.
 “Hello, Monty, how’s my sweetheart?” Dr. Secor asked a tan Burmese python as it slithered up his shoulders. “Monty’s a good snake, aren’t you?”
“Oh yeah,” Mr. Nelson said, as if he was referring to his toy Pomeranian upstairs. But Mr. Nelson never let his guard down, even as he let another snake flick its tongue over his eyebrow. “Any of these could kill you if you let it,” he said, somehow cheerfully.
It was feeding day. The snakes had not eaten for two weeks. They were now about to perform one of the most extraordinary acts of metabolism in the animal kingdom — a feat that Dr. Secor has been exploring for a quarter of a century.
He has been finding adaptations throughout the snake’s entire body, such as the ability to rapidly expand organs and then shrink them back down. His findings offer tantalizing clues that might someday be applied to our own bodies as medical treatments.
Mr. Nelson opened the cage that held a dark gray Burmese python named Haydee, and heaved in a large rat.
The rat stood frozen in the corner, but Haydee ignored her new roommate for several minutes. She slowly raised her metallic-colored head, indifferently flicking her tongue. And suddenly Haydee became a missile.
She shot across the cage, snagged the rat with her upper teeth and wrapped her thick midriff around her victim. Between Haydee’s coils, the upended rat was still visible, its back legs and tail jerking in the air. It heaved for a while with rapid breaths, then stopped.
Haydee loosened her grip and raised her head to the door, as if wondering if more rats were in the offing. Then she turned back to her prey, nose to nose, and opened her mouth wide.
 She used her side teeth to pull her head over the dead rodent. Her jaws stretched apart to make room, and she worked the rat into her expanding throat. She arched her head up toward the door, as if offering her human audience a chance to say farewell to the rat as its hind legs and tail slid into its esophagus.
But Haydee’s performance was far from over. Pythons and several other kinds of snakes regularly eat a quarter of their body weight at once. Sometimes a meal will outweigh them. Over the next few days, they break their prey down and absorb almost all of it.
Dr. Secor started studying how these snakes alternate between fasts and feasts since graduate school, and has been developing new ways to study them. These days, he is collaborating with genome experts to investigate the animals in molecular detail. Together the scientists are finding that snakes perform a genetic symphony, producing a torrent of new proteins that enable their body too quickly turn into an unrivaled digestion machine.
“I am a huge fan — they’re taking state-of-the-art genomics and pushing the boundaries on what we can understand,” said Harry Greene, a Cornell University snake expert who is not involved in the project. “It’s not too preposterous to imagine that could have fantastic human health implications.”
As a graduate student, Dr. Secor studied how sidewinder rattlesnakes survived as they went from long fasts to gulping down whole animals. He wondered how much energy they needed to digest a meal.
When he came to U.C.L.A. as a postdoctoral researcher, he decided to find out. He fed mice to his rattlesnakes and then put them in a sealed box. He could analyze samples of air from the box to track how much oxygen they breathed to burn fuel.
“In two days, I had these numbers that made no sense,” he said.
When mammals feed, their metabolic rate goes up between 25 and 50 percent. The rattlesnakes jumped about 700 percent.
Dr. Secor switched to pythons and found that they reached even greater extremes. If a python eats a quarter of its body weight, its metabolic rate jumps 1,000 percent. But pythons can eat their whole body weight if Dr. Secor has enough rats on hand. In those cases, their metabolic rate can soar by 4,400 percent, the highest ever recorded for an animal.
For comparison, a horse in full gallop increases its metabolic rate by about 3,500 percent. But whereas a horse may gallop for a couple minutes in the Kentucky Derby, a python can keep its metabolic rate at its extreme elevation for two weeks.
Dr. Secor has spent years investigating what the snakes are doing with all that extra fuel. For one thing: making stomach acid.
We add some acid to our stomach a few times a day to handle our regular meals. But when a python is fasting, its stomach contains no acid at all. Its pH is the same as water.
Within a few hours of swallowing an animal, Dr. Secor found, a snake produces a torrent of acid that will remain in its stomach for days, breaking down the snake’s prey.
Meanwhile, the snake’s intestines go through a remarkable growth spurt. Intestinal cells have fingerlike projections that soak up sugar and other nutrients. In a snake, those cells swell, their fingers growing five times longer. A python can triple the mass of its small intestines overnight. Suddenly its digestive tract can handle the huge wave of food coming its way.
Once all that food is circulating through the snake’s bloodstream, its other organs have to cope with it. Dr. Secor and his colleagues have found that the rest of a snake’s body responds in a similarly impressive fashion. Its liver and kidney double in weight, and its heart increases 40 percent.
By the time the rat in Haydee’s esophagus makes it to the end of her large intestines, all that remains is a packet of hair. Everything else will be coursing through her body, much of it destined to end up as long strips of fat. In the meantime, her gut will shrink, her stomach will turn watery again and her other organs will return to their previous size.
From an evolutionary point of view, Dr. Secor could see how this drastic reversal made sense. “Running all this stuff is a tremendous waste of energy,” he said. “Why keep things up and running when you don’t use them?”
But how snakes managed this feat was harder for Dr. Secor to explain. Other scientists couldn’t help him.
When he showed pictures of shrinking snake intestines to pathologists, they were baffled. “They’d say, ‘Your animals are sick. They’re dying. They have parasites that are ravaging their intestines,’” Dr. Secor said. “I’d say, ‘No, they’re healthy.’ They just shook their heads and sent me on my way.”
Measuring their oxygen intake and looking at their intestines under microscopes could only take Dr. Secor so far. He asked colleagues who studied DNA what it would take to track how snake genes turned on and off during digestion.
“And they’d say, ‘You couldn’t do it,’” Dr. Secor recalled. “It would take years and years and years, because you’d have to pull each one out, and then you have to find out what it was.”
Then in 2010, Dr. Secor met Todd Castoe, an expert on sequencing reptile DNA, who jumped at the chance to help Dr. Secor make sense of his snakes.
“The metabolism is crazy — so much of this is extreme and unexpected,” said Dr. Castoe, who now teaches at the University of Texas at Arlington.
Dr. Castoe and Dr. Secor launched a collaboration to understand snakes at the molecular level. In 2013, they and their colleagues published the genome of the Burmese python. Now they had a catalog of every gene that snakes might use during digestion.
 Since then, the scientists have tracked how the snakes use these genes. Dr. Secor and his students dissect snakes either during a fast or after they have had a meal. The researchers examine every organ and preserve samples for later study.
 “Everything is pickled or frozen,” Dr. Secor said.
He ships some of the material to Dr. Castoe in Texas, who cracks open the snake cells. Dr. Castoe’s team then finds molecular clues to which genes are active in different organs.
The researchers were shocked to find that, within 12 hours of swallowing prey, a vast number of genes become active in different parts of a snake. “You might expect maybe 20 or 30 genes to change,” said Dr. Castoe. “Not 2,000 or 3,000.”
A number of the genes are involved in growth, the researchers have found, while others respond to stress and repair damaged DNA.
It is a strange combination that scientists have not seen in animals before. Dr. Castoe speculates that snakes use their growth genes far more intensely than, say, a growing human child would.
That overdrive allows the snakes to double the size of organs in a matter of hours and days. But it may also come at a cost: The cells are growing and dividing so fast that they don’t have time to be careful. Along the way, they produce a lot of malformed proteins that damage the cells.
When the swollen organs shrink back to normal, it appears that the snakes may simply shut down their repair genes, so that their cells are no longer shielded from their self-inflicted damage.
“The whole growth thing collapses,” Dr. Castoe speculated.
Even among snakes, the fast-and-feast way of life is unusual, having independently evolved only a few times.
By looking at other such fasting snakes, the scientists have found some of the same changes in gene activity. They are focusing on this smaller set of genes.
“It’s like we’re cutting away pieces of the pie, and we just want the juiciest part,” said Dr. Castoe.
If he and Dr. Secor can figure out what happens in snakes, it might be possible to elicit some of their powers in our own bodies, since we share many genes in common with animals.
The scientists suspect that the snakes orchestrate their transformation with a few molecular triggers. Some genes may cause many other genes to switch on in an organ and make it grow. If scientists could find those triggers, they might be able to regenerate damaged tissue in people.
Alternatively, doctors might mimic the way that snakes rapidly — but safely — reverse their growth. There might be clues in their biology for how to stop the uncontrolled growth of cancers.
“If you knew the answers to all that, you’d probably have drugs that could cure dozens of diseases,” Dr. Castoe said.
But Dr. Castoe sees a lot of work ahead before any such benefits emerge. For now, he and his colleagues have no idea what the triggers are in snakes.
To find out, they are now looking at snakes within just a few hours of catching prey. They can see changes in the snake cells. But those changes occur too quickly to be the result of switching on genes. It is possible that the snakes are refolding the proteins that already exist in their cells, so that they do new things.
“I’d love to put together the whole pathway,” Dr. Secor said. “But we’re not even close to figuring this all out.”

Student discovers 18 new species of aquatic beetle in South America

JUNE 22, 2020

by Brendan M. Lynch, University of Kansas
It would be striking for a seasoned entomologist with decades of fieldwork to discover such a large number of species unknown to science. But for University of Kansas student Rachel Smith, an undergraduate majoring in ecology & evolutionary biology, the find is extraordinary: Smith recently published a description of 18 new species of aquatic water beetle from the genus Chasmogenus in the peer-reviewed journal ZooKeys.
"The average size of these beetles, I would say, is about the size of a capital 'O' in a 12-point font," said Smith of the collection of new species. "They spend a lot of their life in forest streams and pools. They're aquatic, so they're all great swimmers—and they can fly."
The research involved Smith traveling to Suriname to perform fieldwork as well as passing countless hours in the lab of Andrew Short, associate professor of ecology & evolutionary biology and associate curator with KU's Biodiversity Institute, who co-wrote the new paper.
Smith said many of the aquatic beetle species are virtually indistinguishable simply by looking at them, even under a microscope.
"Something unique and fascinating about this genus, particularly the ones I worked on, is that many look almost exactly the same," she said. "Even to my trained eye, it's hard to tell them apart just based on external morphology. Their uniqueness is in there but kind of hidden in this very uniform external morphology."
To identify the new species, Smith compared DNA evidence from the aquatic beetles with a few external morphological differences that could be observed. But this was not enough: Much of Smith's work also hinged on dissecting these tiny specimens collected in northeastern South America to spot key differences in their internal anatomy.
"Because it's difficult to tell them apart from external morphology, you kind of have to go inside," she said. "I ended up doing over 100 dissections of these beetles to extract the male genitalia and look at it under a microscope. That really was the true way to tell them apart. Ultimately, it came down to male genitalia and genetic divergence that I used to delimit many of these species."

Are protected areas effective at maintaining large carnivore populations?

JUNE 22, 2020

A recent study, led by the University of Helsinki, used a novel combination of statistical methods and an exceptional data set collected by hunters to assess the role of protected areas for carnivore conservation in Finland.

Overall, protected areas do not harbor higher densities of large carnivore species than unprotected lands. These areas even had declining wolverine densities within their limits while populations outside remained overall stable over a 30-year study period. The study was published in the journal Nature Communications.

The international group of authors, led by Dr. Julien Terraube from the Faculty of Biological and Environmental Sciences at the University of Helsinki, proposes that the results do not indicate that protected areas are unimportant for carnivore conservation, as they may support seasonal habitats and prey for these highly mobile species. However, the outcomes highlight complex socio-ecological pressures on carnivore populations that vary in both time and space and affect the conservation outcomes of protected areas. For example, the largest Finnish protected areas are located in Lapland, and due to their sizes these areas are most suitable for large carnivores. However, the areas seem unable to maintain stable wolverine populations, which may be linked to increased conflicts with herders in the reindeer husbandry area.

Related Posts with Thumbnails