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What do frogs eat — and other froggy facts you never wanted to know

Frogs are by far the most widespread amphibians — they make up almost 90% of all the current amphibian species. Frogs generally spend their time around bodies of freshwater, in areas that remain wet even during the summer. So, naturally, this influences their eating patterns.

Adult individuals of almost all species are carnivorous, most often preying on invertebrates such as worms, snails, slugs, and arthropods. It’s sometimes said that frogs are “insectivores”, but that’s not technically true. They’re often generalist carnivores, eating pretty much anything they can swallow. Sometimes, they will hunt reptiles, amphibians, even small mammals. They sometimes even engage in cannibalism, while some species mostly feed on plants.

When it comes to what frogs eat, the answer is both simple and complicated.

Image credits: Ed van duijn.

What frogs eat — the tadpole edition

Frogs typically have five life stages. They start out as eggs and then become tadpoles, tadpoles with legs, young frogs, and adult frogs. During their tadpole stage, they’re extremely different from their adult stage. Tadpoles generally lack limbs and have a tail, they breathe through gills and live exclusively in water. The metamorphosis from tadpole to frog involves some major biological changes, including a change in diet.

The diet of tadpoles is also different from that of adults. Tadpoles are typically herbivorous and their preferred food is algae. They also scrape leaves from the pond, if available. If you want to feed tadpoles (though you shouldn’t start randomly feeding tadpoles in the wild), greens are probably your best options. Lettuce, broccoli, baby spinach all work great.

However, tadpoles aren’t exactly picky. Most species are carnivorous at the tadpole stage, but in a pinch, almost all tadpoles would eat insects, mosquito larvae, smaller tadpoles, or even carcasses. In fact, several species have been found to be cannibalistic at the tadpole stage, and tadpoles that develop legs early are more likely to be eaten, so late bloomers are more likely to survive.

It’s a tough life for a tadpole, and being picky with food is a luxury you can’t really afford.

A curious (and probably hungry) tadpole. Image in public domain.

Adult frogs and what they eat

Frogs don’t really roam much; they tend to stick close to the water that is so crucial to them. Although some species can travel for several kilometers, it’s common for frogs to stay within a few hundred meters (usually less than 500 meters) around their pond area. As a result, they have to eat things that they can reliably catch around their area.

This being said, frogs will often eat any living thing they can fit into their mouths. If it flies, walks, or crawls and it’s not too big, frogs will often have a go at it. Aside from the common prey (bugs, worms, snails, slugs), they will eat smaller mammals, reptiles, fish, or even small marsupials. The list isn’t limited to only these. Frogs are true generalist predators, and anything small enough to be eaten by a frog could be eaten by a frog. Moths, butterflies, crickets, even bees — all could be found on frogs’ menus.

Frogs hunt by using their specialized tongue and spit. Frog spit is one of the stickiest substances on the planet, and frogs’ tongues can extend out at a whopping 4 meters per second, and can be retracted in 0.07 seconds — five times faster than you can blink.

Generally, frogs like to hunt. They don’t really like carrion or leftovers from other animals (though on very rare occasions, they might also eat it). When they eat things like slugs or other mollusks, they generally swallow the shell whole. They don’t really pay much attention, and if they’re hungry and they can snag something, they’ll generally go for it.

Drawing of several species of frogs. Image credits: Wiki Commons.

 This being said, a few species also eat plant matter; for instance, the tree frog Xenohyla truncata is partly herbivorous, and its diet includes a large proportion of fruit. Several other species of frogs have been found to consume significant quantities of plants, and the diet of Euphlyctis hexadactylus consists of 80% leaves and flowers (though its juveniles are insectivores.

During the winter, frogs hibernate, slowing their metabolism and surviving until spring from the food they’ve consumed. Some species dig a burrow for themselves, others bury themselves in leaves, while some merely sink to the bottom of the pond, half-covered in mud. During hibernation, they obviously don’t eat anything. Fun fact: some frogs can indeed freeze and survive frozen for months, coming back to life when they thaw.

What does the common frog eat

There are over 5,000 species of frogs, making up around 88% of all amphibian species on Earth, and researchers are constantly finding new species as well. Here, we’ve tried to address the question of what frogs eat generally, but let’s take a moment to talk about the common frog.

The common frog (Rana temporaria), true to its name, can be found across most of Europe, including Scandinavia, Ireland, and the Balkans. It can also be found across vast swaths from Asia, up to Japan. By and large, it’s the most common frog species out there.

The common frog’s eating patterns are greatly influenced by the time of year, and like many other frogs, they also enter a type of hibernation. When they are active, they mostly eat invertebrates: snails, worms, wood lice, and spiders. They have a keen sense of smell and can detect worms or other prey of interest. They also eat larvae from other common frogs.

What about toads, what do toads eat?

Although the difference between toads and frogs seems significant, and you occasionally come across someone who’s quick to point that out, the use of the name toads and frogs has no taxonomic justification. It’s more of an esthetic consideration. ‘Frog’ usually refers to species that are either fully aquatic or semi-aquatic and have moise, smooth skins, while toads are terrestrial and have dry, warty skins (although there are exceptions).

The European Common Frog (Rana temporaria, left) & European Toad (Bufo bufo, right) hanging out in a London garden. Image credits: Thomas Brown.

As a result, because toads and frogs are so similar, they eat kind of the same thing. Toads mainly eat insects and other arthropods. They often enjoy eating things like worms and crickets. Sometimes, toads will also hunt prey like small mammals or even other amphibians.

Notably, frogs and toads are useful as they can keep the insect population under control. But they can also cause substantial damage, and several species of frogs and toads are invasive. A notable example dates from 1935 when cane toads from Puerto Rico were brought to Australia to control the sugarcane beetle population. The idea backfired spectacularly. Out of 102 toads that were introduced, their numbers grew to over 2 billion. They killed the beetles alright, but they killed a ton of native species as well and have become a major environmental problem.

At the end of the day, there’s a bunch of different frogs out there, with different eating patterns. Generally, frogs are indiscriminate predators, but some have more varied preferences. Undoubtedly, there’s still a lot left to learn about species of frogs, especially species from remote areas.

Frogs are also faced with a number of environmental threats; the common frog may be common, but other species are under a great deal of pressure. Out of the around 5,000 species of frogs we know, 737 species are endangered and 549 are critically endangered, and over 100 have probably gone extinct in recent times already (that we know of — the reality is quite possibly even worse). Among the biggest environmental threats, frogs are faced with are habitat destruction and other invasive species.

Researchers successfully regrow limbs on frogs. They want to do the same thing with humans

Most animals have pretty good injury repair capabilities, but when it comes to lost limbs, only a select few can regrow them. The rest, including humans, have little they can do to repair such injuries. But as a new study shows, with the right treatments, our bodies may be hacked and “convinced” to regrow lost limbs. Although the study focused on frogs, which are obviously very different from humans, the proof-of-concept study suggests that this approach could work on many animals, including humans.

The African clawed frog (Xenopus laevis). Image via Wiki Commons.

Limb regeneration is a new frontier in biomedical science. It’s something we’ve long considered outside the realm of possibility, restricted only to superheroes and myth, but research is bringing it closer and closer to reality.

While many things differentiate humans from frogs, neither we nor they are able to regenerate limbs. So researchers at Tufts University and Harvard University’s Wyss Institute used frogs (specifically, the African clawed frog or Xenopus laevis) as a proof of concept. X. laevis is often used in research as it is easy to handle, lays eggs throughout the year, and for a model organism, shares a close evolutionary relationship with humans.

The researchers triggered the regrowth of a lost leg using a five-drug cocktail that they applied in a wearable silicone bioreactor dome that sealed the drugs over the stump for just 24 hours. After the treatment was administered, the regenerative process was kickstarted, and over the course of an 18-month period, the frogs regrew an almost fully functional leg.

“It’s exciting to see that the drugs we selected were helping to create an almost complete limb,” said Nirosha Murugan, research affiliate at the Allen Discovery Center at Tufts and first author of the paper. “The fact that it required only a brief exposure to the drugs to set in motion a months-long regeneration process suggests that frogs and perhaps other animals may have dormant regenerative capabilities that can be triggered into action.”

The experiment was repeated on dozens of frogs, and while not all of them regrew limbs, most did — including bone tissue and even toe-like structures at the end of the limb (though these weren’t supported by bone). It’s not a magic elixir, and the treatment is not perfect, but the drug cocktail delivered through the wearable bioreactor really does seem capable of regrowing limbs.

Regrowth of soft tissue. The MDT group (bottom) represents the five-drug cocktail treatment. Image credits: Murugan et al (2022).

The researchers essentially hacked the biological pathways that enable the growth and organization of tissue — much like in an embryo. This is why the treatment was only applied once, over the course of a day; meanwhile, other approaches involve numerous interventions over the course of the process.

“The remarkable complexity of functional limbs suggests that the fastest path toward this goal may lie in triggering native, self-limiting modules of organogenesis, not continuous micromanagement of the lengthy process at the cell and molecular levels,” the researchers write in the study. “We implemented this via a short exposure of limb amputation wounds to a wearable bioreactor containing a payload of five select biochemical factors.”

The first stage is the formation of a mass of stem cells at the end of the stump, which was then used to gradually reconstruct the limb. It’s essential that this structure is covered with the dome as quickly as possible after amputation to ensure its protection and activation. This treatment would be ideally applied right after amputation.

“Mammals and other regenerating animals will usually have their injuries exposed to air or making contact with the ground, and they can take days to weeks to close up with scar tissue,” said David Kaplan, Stern Family Professor of Engineering at Tufts and co-author of the study. “Using the BioDome cap in the first 24 hours helps mimic an amniotic-like environment which, along with the right drugs, allows the rebuilding process to proceed without the interference of scar tissue.”

At first, researchers tried using the protective dome with a single drug, progesterone. Progesterone is a steroid hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. This alone triggered some limb growth, but the resulting limb was essentially a non-functional spike. Each of the other four drugs fills a different role, ranging from reducing inflammation and the stopping of scar tissue formation to the promotion of growth of new nerves, blood vessels, and muscles. It’s the combination of all these together that leads to a nigh-functional limb.

Researchers note that while the limbs weren’t 100% identical to “normal” limbs, they featured digits, webbing, and detailed skeletal and muscular features. Overall, the results show the successful “kickstarting” of regenerative pathways

The plan now is to move on to mammal research. Despite the differences between frogs and mammals, researchers say that the biggest difference lies in the “early events of wound healing” — if these early processes can be understood and replicated, then there’s no apparent reason why this couldn’t be applied to mammals, and ultimately humans as well.

“The goal of triggering latent tissue-building routines to regrow limbs in humans may be achieved by identifying and exploiting principles observed in highly regenerative organisms,” the researchers conclude.

The study was published in the journal Science Advances.

The world’s first ‘living machines’ can move, carry loads, and repair themselves

Researchers at the University of Vermont have repurposed living cells into entirely new life-forms — which they call “xenobots”.

The xenobot designs (top) and real-life counterparts (bottom).
Image credits Douglas Blackiston / Tufts University.

These “living machines” are built from frog embryo cells that have been repurposed, ‘welded’ together into body forms never seen in nature. The millimeter-wide xenobots are also fully-functional: they can move, perform tasks such as carrying objects and healing themselves after sustaining damage.

This is the first time anyone “designs completely biological machines from the ground up,” the team writes in their new study.

It’s alive!

“These are novel living machines,” says Joshua Bongard, a professor in UVM’s Department of Computer Science and Complex Systems Center and co-lead author of the study. “They’re neither a traditional robot nor a known species of animal. It’s a new class of artifact: a living, programmable organism.”

“It’s a step toward using computer-designed organisms for intelligent drug delivery.”

The xenobots were designed with the Deep Green supercomputer cluster at UVM using an evolutionary algorithm to create thousands of candidate body forms. The researchers, led by doctoral student Sam Kriegman, the paper’s lead author, would assign the computer certain tasks for the design — such as achieving locomotion in one direction — and the computer would reassemble a few hundred simulated cells into different body shapes to achieve that goal. The software had a basic set of rules regarding what the cells could and couldn’t do and tested each design against these parameters. After a hundred runs of the algorithm, the team selected the most promising of the successful designs and set about building them.

The design of the xenobots.
Image credits Sam Kriegman, Douglas Blackiston, Michael Levin, Josh Bongard, (2020), PNAS.

This task was handled by a team of researchers at Tufts University led by co-lead author Michael Levin, who directs the Center for Regenerative and Developmental Biology at Tufts. First, they gathered and incubated stem cells from embryos of African frogs (Xenopus laevis, hence the name “xenobots”). Finally, these cells were cut and joined together under a microscope in a close approximation of the computer-generated designs.

The team reports that the cells began working together after ‘assembly’. They developed a passive skin-like layer and synchronized the contractions of their (heart) muscle cells to achieve motion. The xenobots were able to move in a coherent fashion up to days or weeks at a time, the team found, powered by embryonic energy stores.

Later tests showed that groups of xenobots would move around in circles, pushing pellets into a central location, spontaneously and collectively. Some of the xenobots were designed with a hole through the center to reduce drag but the team was able to repurpose it so that the bots could carry an object.

It’s still alive… but on its back?

A manufactured quadruped organism, 650-750 microns in diameter.
Image credits Douglas Blackiston / Tufts University.

One of the most fascinating parts of this already-fascinating work, for me, is the resilience of these xenobots.

“The downside of living tissue is that it’s weak and it degrades,” says Bongard. “That’s why we use steel. But organisms have 4.5 billion years of practice at regenerating themselves and going on for decades. We slice [a xenobot] almost in half and it stitches itself back up and keeps going. This is something you can’t do with typical machines.”

“These xenobots are fully biodegradable,” he adds, “when they’re done with their job after seven days, they’re just dead skin cells.”

However, none of the team’s designs was able to turn itself over when flipped on its back. It’s an almost comical little Achilles’ Heel for such capable biomachines.

The manufacturing process of the xenobots.
Image credits Sam Kriegman, Douglas Blackiston, Michael Levin, Josh Bongard, (2020), PNAS.

Still, they have a lot to teach us about how cells communicate and connect, the team writes.

“The big question in biology is to understand the algorithms that determine form and function,” says Levin. “The genome encodes proteins, but transformative applications await our discovery of how that hardware enables cells to cooperate toward making functional anatomies under very different conditions.”

“[Living cells] run on DNA-specified hardware,” he adds, “and these processes are reconfigurable, enabling novel living forms.”

Levin says that being fearful of what complex biological manipulations can bring about is “not unreasonable”, and are very likely going to result in at least some “unintended consequences”, but explains that the current research aims to get a handle on such consequences. The findings are also applicable to other areas of science and technologies were complex systems arise from simple units, he explains, such as the self-driving cars and autonomous systems that will increasingly shape the human experience.

“If humanity is going to survive into the future, we need to better understand how complex properties, somehow, emerge from simple rules,” says Levin. “If you wanted an anthill with two chimneys instead of one, how do you modify the ants? We’d have no idea.”

“I think it’s an absolute necessity for society going forward to get a better handle on systems where the outcome is very complex. A first step towards doing that is to explore: how do living systems decide what an overall behavior should be and how do we manipulate the pieces to get the behaviors we want?”

The paper “A scalable pipeline for designing reconfigurable organisms” has been published in the journal PNAS.

The slimy difference between toads and frogs

Can you tell the difference between a frog and a toad? You might think that it’s easy, toads are warty and frogs have smooth, slimy skin. However, it’s not always as straightforward as it seems.

In general, there are some key differences between toads and frogs that make it possible to distinguish between them quite easily. If you’ve seen a frog, it’s probably been in or near a pond, while you’re more likely to encounter toads in drier areas. Toads crawl, have bumpy skin, and usually lay their eggs in large strands. Frogs jump around, have smooth skin, and lay their eggs in clumps. There are a few more physical differences that aren’t possible to spot so easily: toads have poison glands behind their eyes, distinctive chest cartilage, and lack teeth.

A typical frog and toad. Image credits: Thomas Brown.

What we consider toads are the “true toads”, which are part of a single family, Bufonidae, made up of 600 species. Most of them have the typical traits that we expect in toads. However, there are over 7,000 species of toads and frogs in the world and it can easily get quite confusing to know what is a frog and what is a toad. They have similar features because they both make up the order Anura in the animal kingdom. Toads actually make up one group of frogs, so all toads are frogs, but not all frogs are toads.

The TOAD Atelopus certus. Image credits: Brian Gratwicke.

Not all frogs and toads look or behave how we expect them. Some frogs look like toads with plain, bumpy skin, and some toads have smooth, brightly coloured skin. For example, the Harlequin Toads (genus Atelopus) are “true toads”, but you might think that they are frogs on first glance, because they are coloured in rich jewel shades and have smooth skin. They are often called frogs.

On the other hand, there are also frogs that get lumped in as “toads” just because they don’t adhere to typical frog beauty standards. This means that they could be drab-looking, have bumpy skin, and live more on land than near water. Indeed, hundreds of frogs from many different families, such as the Australian ground frogs (Myobatrachidae), fire-belly toads (Bombinatoridae), and the Asian toads (Megophryidae), get called toads although they are not.

The FROG Bombina variegata. Image credits: Miltos Gikas.

It can get confusing because the names “frog” and “toad” are used interchangeably in the common names for amphibians. For example, Bombina bombina is a frog but its common names include European fire-bellied toad, ringing frog, fiery toad, and fire frog. Therefore, some frogs are called toads although they are not, just because they look similar. The reverse also occurs, as Harlequin toads are often called Harlequin frogs. However, the easiest way to know is to look at the scientific family. If its in Bufonidae, it’s a “true toad”.

All in all, “true toads” are the only official toads and can usually be distinguished by their appearance. However, there are also some froggy toads and toady frogs.

Dead frog killed by Chytridiomycosis. Credit: Wikimedia Commons.

An amphibian fungus has caused the worst mass extinction in recent history

Dead frog killed by Chytridiomycosis. Credit: Wikimedia Commons.

Dead frog killed by Chytridiomycosis. Credit: Wikimedia Commons.

A fungus that gruesomely kills frogs and other amphibians is responsible for the biggest decline in wildlife in recorded history. In the past 50 years since the first outbreaks were signaled by biologists, the disease, known as chytridiomycosis, has caused the extinction of 90 species and wiped out 90% of the populations of another 124 species.

Chytridiomycosis is caused by a fungus called Batrachochytrium dendrobatidis — or Bd for short. The fungus is believed to have originated in Asia where it was confined to certain hotspots. However, it started to spread across the world in the early 20th century, during a period when international trade was booming. Along with spices, porcelain, and various other goods, Western sailors also carried Bd from port to port via infected stowaway animals. Today, Bd is present in over 60 countries across five continents.

Biologists first noticed in the ’70s and ’80s that amphibian populations began to suddenly decline or outright disappear. It wasn’t until 1998 that this decline was associated with Bd and the scope of the crisis became apparent. But a recent analysis suggests that the situation is even worse than some have feared. According to new data compiled by researchers at the Australian National University, the fungus is responsible for the decline of 501 species of frogs and other amphibians — that’s 6.5% of all known amphibians. Australia, Central America, and South America are particularly hard hit, say the authors.

“Highly virulent wildlife disease, including chytridiomycosis, is contributing to the Earth’s sixth mass extinction,” said Dr. Ben Scheele of The Australian National University in Canberra, the lead author of the new study.

“We’ve lost some really amazing species.”

Each bar represents a single species hit by the fungus. The color shows the extent of population decline or extinction. Credit: Scheele et al., Science.

Each bar represents a single species hit by the fungus. The color shows the extent of population decline or extinction. Credit: Scheele et al., Science.

The fungus is really after nutrients found on the amphibians’ skin. However, it also feasts on the tissue of the animals, eating away their skin and triggering fatal heart attacks. The disease spreads through the water and can persist outside the host which makes traditional tactics for fighting invasive species useless. This isn’t some feral cat or rodent, but a microorganism that virtually permeates the entire environment once it gets a footing.

“It’s a staggering thing to consider,” said one of the study’s authors, Jonathan Kolby, in an interview with the Washington Post. “We’ve never before had a single disease that had the power to make multiple species extinct, on multiple continents, all at the same time.”

There is a glimmer of hope, though. The findings suggest that 60 species have shown signs of recovery. Perhaps some sturdy individuals have the necessary adaptations to keep the disease at bay. But no one can tell for certain whether amphibians are starting to develop an evolutionary edge against the fungus or it’s just a matter of time before a new outbreak comes to deliver the killing blow.

As if Bd wasn’t enough, amphibian species across the world are threatened by habitat loss, exploitation, and climate change — these are still the main threats for thousands of species. The best thing we can do right now is to shelter currently untouched population from Bd by restricting access to sanctuaries. Some research groups are breeding individuals from contaminated habitats in captivity in hopes of averting a species’ total annihilation.

“It’s really hard to remove chytrid fungus from an ecosystem — if it is in an ecosystem, it’s pretty much there to stay unfortunately. This is partly because some species aren’t killed by the disease,” Scheele said.

“On the one hand, it’s lucky that some species are resistant to chytrid fungus; but on the other hand, it means that these species carry the fungus and act as a reservoir for it so there’s a constant source of the fungus in the environment.

But, the truth is that there is not one thing we can do to significantly improve the odds of survival of infected habitats or, for that matter, stave off the spread of Bd. And this makes this killer fungus incredibly scary.

Juliet with Teresa Camacho Badani. Credit: by Robin Moore, Global Wildlife Conservation.

Romeo, once the loneliest the frog in the world, finds a mate!

Romeo the bachelor Sehuencas water frog. Credit: Dirk Ercken and Arturo Muñoz.

More than ten years ago, biologists collected Romeo — a Sehuencas water frog — from a stream in Bolivia. They knew that the species was in big trouble and a conservation effort had to be urgently ramped up, but despite numerous subsequent searches, no other specimen had been found. Things were looking pretty bleak for the loneliest frog in the world until recently when an expedition formed by Global Wildlife Conservation and the Museo de Historia Natural Alcide d’Orbigny rescued five individuals: three males and two females. It looks Romeo may have found his Juliet after all!

“It is an incredible feeling to know that thanks to everyone who believes in true love and donated for Valentine’s Day last year, we have already found a mate for Romeo and can establish a conservation breeding program with more than a single pair,” Teresa Camacho Badani, the museum’s chief of herpetology and the expedition leader, said in a press release. “Now the real work begins—we know how to successfully care for this species in captivity, but now we will learn about its reproduction, while also getting back into the field to better understand if any more frogs may be left and if so, how many, where they are, and more about the threats they face. With this knowledge we can develop strategies to mitigate the threats to the species’ habitat, while working on a long-term plan to return Romeo’s future babies to their wild home, preventing the extinction of the Sehuencas water frog.”

The expedition team — which included Camacho Badani, veterinarian Ricardo Zurita Urgarte, Sophia Barrón Lavayen, the head of conservation breeding for the K’ayra Center; and researcher Stephane Knoll — spent months analyzing historical records of where the species had originally been found, in order to find the best spots.

Although the researchers looked for the frogs in streams that had the perfect conditions, including in a stream where Camacho Badani had found Sehuencas water frogs ten years ago, they came out empty handed. At the end of one fateful day, when the whole team was exhausted and wet, they decided to try their luck just one more time. So they investigated a waterfall at the end of a stream and much to everyone’s surprise, the daring explorers found the much-sought-after amphibians.

“I thought it was a Quechua Toad (Rhinella quechua), also called an Incachaca Toad, which is a threatened species. I told the team to stay alert because I planned to catch the frog to confirm it wasn’t a Sehuencas Water Frog, and then let it go. I got into the pond while the water splashed all over me and dove my hands into the bottom of the pond, where I managed to catch the frog. When I pulled it out, I saw an orange belly and suddenly realized that what I had in my hands was the long-awaited Sehuencas Water Frog. My first reaction was to yell “I found one!” and the team came running over to help me and pull the frog to safety,” Camacho Badani said in an interview for the Global Wildlife Conservation blog.

Juliet with Teresa Camacho Badani. Credit: by Robin Moore, Global Wildlife Conservation.

Juliet with Teresa Camacho Badani. Credit: by Robin Moore, Global Wildlife Conservation.

The Sehuencas water frog (Telmatobius yuracare) was once commonly found on the bottom of small streams or rivers in the inaccessible Bolivian mountain cloud forests. But a combination of pollution, climate change, and a contagious and deadly pathogen placed Telmatobius on the brink of extinction. The newly rescued frogs, among them a Juliet for Romeo, are currently in quarantine as they acclimate to an environment that replicates the conditions in the wild. Conservationists also want to make sure that the frogs aren’t affected by chytridiomycosis, the infectious disease that claimed most of the wild population.

“We do not want Romeo to get sick on his first date! When the treatment is finished, we can finally give Romeo what we hope is a romantic encounter with his Juliet,” Camacho Badani said.

The expedition was launched after Global Wildlife Conservation completed a successful Valentine’s Day fundraiser last year. People from more than 32 countries were impressed by Romeo’s call for a mate in his Match profile and made donations. The funds were matched by Match for a total of $25,000.

In the future, the team plans to look for more frogs through March to better assess the state of the wild Sehuencas water frog population, as well as also to test for the presence of chytridiomycosis. This way, conservation efforts will be better equipped when the time is right to return Romeo’s offspring to the Bolivian mountain springs where they belong.

Previously, similar efforts successfully boosted endangered amphibian populations such as the Mallorcan midwife toad in Spain or the Kihansi spray toad in Tanzania.

City frogs are more attractive than their countriside cousins, new study shows

Living by the forest may be romantic, but living in a city makes you more attractive to the opposite sex — if you are a túngara frog, at least.

A calling male túngara frog with a large inflated vocal sac. Image credits: Adam Dunn.

Increasingly, recent studies have shown significant differences between urban animals and rural-dwelling creatures from the same species — and this makes a lot of sense. Mankind is causing dramatic changes over a wide range of environments and many creatures are slowly adapting to urban conditions. Just recently, researchers found that some urban spiders are no longer afraid of lights; now, a new study reports that city life makes male frogs more attractive.

The authors, led by Wouter Halfwerk from the Vrije Universiteit Amsterdam, compared the ‘chuck’ calls of frogs living in both urban areas and forests near the Panama Canal.

Previous research had found that creatures, such as birds, frogs, and grasshoppers sing or call differently in noisy urban areas, but it was unclear what the effects of these changes are.

“Urbanization can cause species to adjust their sexual displays, because the effectiveness of mating signals is influenced by environmental conditions,” researchers write in the study. “Despite many examples that show that mating signals in urban conditions differ from those in rural conditions, we do not know whether these differences provide a combined reproductive and survival benefit.”

Now, researchers found that urban frogs “sing” more often and use more complex calls than their rural counterparts. They then recorded these calls and played them back to female túngara frogs in the lab. They found that 75% of the females were more attracted to the more complex urban calls.

It’s not exactly clear why this happens, though researchers suspect it has a lot to with how safe the environment is. While calling out can help you get a mate, it can also draw in predators. Since cities generally have far fewer predators, frogs are free to let ‘er rip.

“It definitely shows that if you change the abundance of predators, parasites and mates, that induces a strong evolutionary response,” says Halfwerk.

However, city environments are also more fragmented, which means it’s more difficult to find a mate. So it’s possible that frogs developed their calls because they have to signal more often.

“It is harder for males to get mates in the city and so that is why they even have to work harder than their forest counterparts to get the females,” said Halfwerk.

The team now aims to carry out genetic studies, as well as a large-scale breeding project, to see how these characteristics are passed down through the generations.

However, an important takeaway is that human activity is rapidly changing natural habitats. Creatures are forced to adapt — and sometimes, some of them are very successful, but unfortunately, other times they are not — so urbanization has clearly become a strong selective agent.

The study was published in Nature Ecology and Evolution.

 

Frog pre-amputation.

Experimental bioreactor helps frogs regenerate lost limbs

We’re one leg closer to developing functional limb regeneration.

Frog pre-amputation.

Xenopus laevis pre-amputation
Image credits Celia Herrera-Rincon / Tufts University.

A team of researchers from the Tufts University wishes that everyone could lose a foot and have it, too. The group successfully “kick-started” partial tissue regrowth in adult African clawed frogs (Xenopus laevis) through the use of a bioreactor and electroceutical (electrical cell-stimulating) techniques.

The cradle of life

“At best, adult frogs normally grow back only a featureless, thin, cartilaginous spike,” says senior author Michael Levin, developmental biologist at the Tufts University’s Allen Discovery Center.

“Our procedure induced a regenerative response they normally never have, which resulted in bigger, more structured appendages. The bioreactor device triggered very complex downstream outcomes that bioengineers cannot yet micromanage directly.”

The scientists split up the frog models into three groups — one experimental, one control, and one ‘sham’ group. Each animal had one of its hindlimbs amputated for the trial. Next, they 3D printed a “wearable bioreactor” out of silicon and filled it with hydrogel (a tissue-like mix of water and polymers). This hydrogel was mixed with certain silk proteins that provided a “pro-regenerative environment” and “enhanc[ed] bone remodeling”, according to the authors.

Next came the trial proper: frogs in the experimental and sham groups received the bioreactor (which was sutured on) immediately after the amputation procedure. The difference between the two is that the hydrogel for the experimental group was further laced with progesterone. Progesterone is a hormone that works to prepare the body for pregnancy but has also been shown to promote tissue repair, from nerves to bone. The control group received no treatment. Twenty-four hours later, the devices were removed.

Observations carried out at various times over the following nine-and-a-half months show that the bioreactor induced a degree of regeneration in the experimental group that had no counterpart in the other two groups. Instead of the typical spike-like structure, frogs treated with the bioreactor-progesterone combo re-grew a paddle-like structure — closer to a fully formed limb than what unaided regeneration processes created.

Results comparison.

Image credits Celia Herrera-Rincon et al., 2018, Cell Reports.

“The bioreactor device created a supportive environment for the wound where the tissue could grow as it did during embryogenesis,” says Levin. “A very brief application of bioreactor and its payload triggered months of tissue growth and patterning.”

The regenerated structures of the experimental groups were thicker, had better-developed bones, nerve bundles, and blood vessels. Video footage of the frogs in their tanks also showed that these frogs could swim more like un-amputated ones, the team adds. Scarring and immune responses were also dampened in the bioreactor-treated frogs, suggesting that the progesterone limited the body’s natural reaction to injury in a way that benefited the regeneration process.

So, why exactly did the device work? Genetic tests performed by the team showed that the bioreactor-progesterone combo altered gene expression in cells at the amputation site. Genes involved in oxidative stress, serotonergic signaling, and white blood cell activity were upregulated, while some other signaling-related genes were downregulated.

Regeneration results 2.

Anatomical outcome (bottom) and X-ray images (top) of regenerates formed in adult Xenopus hindlimb amputation after no treatment (Ctrl, A) and after 24-hr combined treatment of drug-loaded device (Prog-device, B–D).
Image credits Celia Herrera-Rincon et al., 2018, Cell Reports.

“In both reproduction and its newly discovered role in brain functioning, progesterone’s actions are local or tissue-specific,” says first author Celia Herrera-Rincon, neuroscientist in Levin’s lab at Tufts University.

“What we are demonstrating with this approach is that maybe reproduction, brain processing, and regeneration are closer than we think. Maybe they share pathways and elements of a common — and so far, not completely understood — bioelectrical code.”

The team plans to expand their research in mammal subjects. Previous research hinted that mice can partially regenerate tissue (such as amputated fingertips) under the right conditions. Life on land, however, hinders this process. “Almost all good regenerators are aquatic,” Levin explains, adding that “a mouse that loses a finger or hand, and then grinds the delicate regenerative cells into the flooring material as it walks around, is unlikely to experience significant limb regeneration.” Still, let’s keep our fingers crossed that the team finds an elegant and efficient solution to this problem — it may, after all, be our limbs that we regrow one day!

But there’s much work to be done until then. Levin says the next step is to add sensors to the device for remote monitoring and optogenetic stimulation, which should give the team a degree of control over how tissues regenerate in the bioreactor. They also plan to expand on their work with bioelectric processes in the hopes of successfully inducing regeneration in the spinal cord, and to the merits of this approach for tumor reprogramming

The paper “Brief Local Application of Progesterone via a Wearable Bioreactor Induces Long-Term Regenerative Response in Adult Xenopus Hindlimb” has been published in the journal Cell Reports.

A 99-million-year-old amber fossil preserved the earliest frog from tropical forests

These 99-million-year-old amber fossils provide the earliest direct evidence of frogs living in wet, tropical forests. Credit: Lida Xing/China University of Geosciences.

Millions of years ago, a juvenile frog was preparing to turn an unsuspecting beetle into a nice, juicy meal. Unfortunately for them, both frog and bug got trapped in sticky resin. Lucky for us, the sap turned to amber, beautifully preserving the fossil frog’s small bones and hints of its tropical environment. This is, in fact, the oldest frog we’ve ever found in a tropical environment — and the oldest frog trapped in amber, for that matter.

Nature’s time capsule

Although frogs have been around for at least 200 million years, being so small and mushy, scientists rarely find early fossils of them. The fossil record is skewed towards species from arid and seasonal environments, which are more robust. This is why the new 99-million-year-old amber fossils are so important to scientists — they provide a very rare insight into the lives of ancient frogs that used to live in wet environments. More than a third of the nearly 7,000 species of frogs live in these wet forests.

“Ask any kid what lives in a rainforest, and frogs are on the list,” said David Blackburn, study co-author and the associate curator of herpetology at the Florida Museum of Natural History, in a statement. “But surprisingly, we have almost nothing from the fossil record to say that’s a longstanding association.”

“These frogs were part of a tropical ecosystem that, in some ways, might not have been that different to what we find today—minus the dinosaurs,” he added.

The amber fossils were recovered from amber deposits in northern Myanmar, Southeast Asia, and have been dated to about 99 million years old. Besides ancient frog remains, the amber fossils also trapped plants, spiders, insects, and marine mollusks.

Amber is like nature’s time capsule. When the tree has a wound (like a broken branch) or if it is attacked by insects or fungi, it exudes the thick resin that plugs up the injury and prevents further damage. In certain conditions of pressure and temperature, typically after becoming covered in sediments, the resin can turn into a solid orange gem whose contents become preserved for millions of years.

For instance, the amber beautifully preserved the tiny frog, which is less than an inch long, visibly showing its skull, forelimbs, and part of its backbone and hind limb. Two other amber fossils contain two forelimbs and an imprint of a frog.

Frogs in amber are quite rare, with previous examples found in the Dominican Republic and Mexico and dating back to only about 40 million and 25 million years, respectively.

One of most well preserved amber fossils in the lot. It contains the skull, forelimbs, part of a backbone and a partial hind limb of an ancient juvenile frog.

One of the most well preserved amber fossils in the lot. It contains the skull, forelimbs, part of a backbone and a partial hind limb of an ancient juvenile frog. Credit: Lida Xing/China University of Geosciences.

The researchers performed a comparative analysis of the ancient frogs, which they dubbed Electrorana limoae, with similar species living today. They uncovered more common ground than differences, suggesting that frogs haven’t really changed that much across the eons. For instance, the ribs and a bone in the cartilaginous plate that supports the tongue suggest Electrorana l. closely resembled some of the species alive today, such as fire-bellied toads and midwife toads. But these are Eurasian species that live in temperate, not tropical, ecosystems.

What’s more puzzling is that the juvenile is missing or hadn’t yet had the chance to develop certain features that herpetologists usually look for in order to discern frog species. Features such as wrist bones, the pelvis, hip bones, the inner ear, the top of the backbone.

For now, Electrorana raises more questions than it answers but Blackburn and colleagues hope to find more specimens trapped in amber.

“We don’t have a lot of single-species frog communities in forests. It seems extremely unlikely that there’s only one. There could be a lot more fossils coming,” the authors wrote in the journal Scientific Reports. 

Scientific reference: Lida Xing et al, The earliest direct evidence of frogs in wet tropical forests from Cretaceous Burmese amber, Scientific Reports (2018). DOI: 10.1038/s41598-018-26848-w. 

Credit: Dirk Ercken and Arturo Muñoz.

Loneliest frog in the world is looking for a Match to save his species

Ten years ago, biologists found a male Sehuencas water frog in Bolivia — and to this day, no other specimen belonging to the same species has ever been seen. Our frog called Romeo is still alone and might as well be the sole surviving member of his species, for all we know. But biologists aren’t ready to give up.

Credit: Dirk Ercken and Arturo Muñoz.

Romeo the bachelor Sehuencas water frog. Credit: Dirk Ercken and Arturo Muñoz.

About a year after he was captured, Romeo started to call for a mate but those calls have slowed down over the years. Desperate times call for desperate measures. Yes, it was time for Romeo to try the online dating game. So a team of conservationists and researchers at Global Wildlife Conservation and the Bolivian Amphibian Initiative partnered with Match in order to find our frog a mate — for his own sake but also that of his entire species. No pressure, Romeo!

Match, the world’s largest dating business, has created a profile for the bachelor frog where prospective mates can learn more about Romeo. For instance, this handsome frog is more of a shy fellow, preferring to linger under rocks, peeking out only when his keepers are out serving him food — I actually know one or two ladies that match this description. Romeo’s favorite meals are earthworms, isopods, and snails. Romeo is also musical, bellowing a distinct breeding call.

“This campaign highlights the crisis that amphibians and even other vertebrate groups are facing in the world. Romeo is similar to some of the other species that came down to only one individual left. There were, and are, others like Lonesome George (the last male of the Pinta Island Tortoise), and Toughie (the last Rabbs’ Fringe-limbed Treefrog),” Arturo Muñoz, founder of the Bolivian Amphibian Initiative and associate conservation scientist of Global Wildlife Conservation, told ZME Science.

“For me personally, Romeo is a messenger, telling us: ‘Look this is happening to me, this is happening to my species, don’t let me go, don’t let my species disappear.’ We as conservationists and as humans have a great opportunity here. We can do something to help this species, and this campaign is an important part of those conservation efforts,” he added.

Credit: Dirk Ercken and Arturo Muñoz.

Ladies, prepare a meal of earthworms for two if you want to win your way to Romeo’s heart. Credit: Dirk Ercken and Arturo Muñoz.

If Romeo isn’t exactly your type, you’re still more than encouraged to donate to his cause. Match and GWC hope to raise $15,000 by Valentine’s Day — money which will fund ten expeditions to the species’ known habitat but also in new places where biologists have never looked. Each donation will be doubled by Match until Valentine’s day.

The Sehuencas water frog (Telmatobius yuracare) was once commonly found on the bottom of small streams or rivers in the montane forests of Bolivia. But a combination of pollution, climate change, all topped by a contagious and deadly pathogen placed Telmatobius on the brink of extinction.

“The species lives in an amazing area, but it is also very difficult to access. The streams of the Bolivian mountain cloud forests are found among very steep slopes and fast rivers, so it can be difficult to get to the best places to search for the frog. In addition, the frog fungal pathogen chytridiomicosis swept through some years ago, and practically all species of the genus in this ecoregion are gone or near extinction. When there may only be small pockets of a species out there, it makes them very difficult to find,” Muñoz said.

There isn’t much time left, however. There are plans to build a dam in the forested area which the Sehuencas water frog once called home and is named after. Besides looking for live specimens, like frogs and tadpoles, the scientists plan on sampling the water too in hope of identifying traces of DNA from the frogs. This way, even if no one spots them, but there’s evidence of their DNA, the team can renew their search afresh.

As things stand now, the future isn’t very bright for the Sehuencas water frog. If researchers do manage to find a female, however, there is still a chance for the species to make an unlikely comeback like the black-footed ferret, golden lion tamarin, and California condor have done in the past. What’s more, although the frog will technically become extinct if Romeo dies alone, the species won’t necessarily have to vanish.

“If all the efforts to find the species fails—which we really hope is not the case!—we are already coordinating with an Australian team that is interested in efforts to save this species through other means. They have the knowledge and tools to collect sperm and tissue for preservation, so we could explore artificial fertilization and even clonation. These are some options that we are starting to consider as a plan B to try to save this species from extinction. Realistically, if this frog dies, the species will likely go extinct. So these efforts—to find him a mate while also collecting sperm and tissue samples—represent our last best hope,” Muñoz said.

Beelzebufo ampinga munching on Cretaceous lunch. Credit: Wikimedia Commons.

Ancient frog with a big appetite may have preyed on small dinosaurs

When you say dinosaur, huge menacing lizards come to mind. Frogs, on the other hand — well, they’re mostly harmless. There are some exceptions, however, such as a few exotic species whose poison seems sourced straight out of hell. Though they might not look like much, frogs have survived T-Rex and all its kin. Moreover, there was a time when some frogs, albeit humongous by our standards, may have actually preyed on dinosaurs.

Beelzebufo ampinga munching on Cretaceous lunch. Credit: Wikimedia Commons.

Beelzebufo ampinga munching on Cretaceous lunch. Credit: Wikimedia Commons.

A frog so big, it might have been a menace even to dinosaurs

This is according to an international team of researchers who studied the bite force of Beelzebufo ampinga, often called the ‘Devil Frog’, an extinct giant frog that lived up to 70 million years ago in Madagascar. It could weigh as much as 5 kg (11 pounds) and — based on bite force trials run on living frogs from the same Ceratophrys genus — researchers estimate it could shut its jaws with a force comparable to formidable mammalian predators such as wolves and female tigers.

The team, which included scientists from Australia, Europe, and the United States, specifically studied the bite force of South American horned frogs. These amphibians are easily recognizable thanks to their trademark round shape and big mouth, earning them the nickname ‘Pacman’. They’re actually too famous and adorable for their own good, being often captured for illegal pet trade.

horned frog

Pacman Frog, Argentine Wide-mouth Frog, Ceratophrys ornata. Credit: Mike Baird, Flickr.

Make no mistake, though — the horned frog can be quite mean. Hiding in the tropical rainforests and freshwater swamps of the Amazon Basin, the frog has no qualms ambushing prey as large as itself. Its diet is based on various types of frogs, snails, lizards, mice, and tadpoles of its own species. Speaking of which, the tadpoles are aggressive from the moment of birth and they often attack each other in the water.

Experimenting with small specimens with heads of about 4.5cm in width, researchers found these packed a biting force of 30 newtons (N) or about 3 kg or 6.6 lbs. Extrapolating for larger, adult specimens, rendered a bite force of almost 500 N. Given what we know about the extinct frog from the same genus, Beelzebufo, the scientists estimated it must have crushed prey between its jaws with a force of up to 2200 N. That’s comparable to the bite of many sizeable mammalian predators, the researchers wrote in Scientific Reports. 

“This would feel like having 50 litres of water balanced on your fingertip,” says Professor Kristopher Lappin, Professor of Biological Sciences at California State Polytechnic University, in a statement.

This means it could very well have preyed on dinosaurs, albeit the smaller, weaker variety.

“This is the first time bite force has been measured in a frog,” Professor Lappin told Phys.org. “And, speaking from experience, horned frogs have quite an impressive bite, and they tend not to let go. The bite of a large Beelzebufo would have been remarkable, definitely not something I would want to experience firsthand.”

Of course, there’s quite a lot of speculation involved. There’s no evidence the ancient frog ate small or juvenile dinosaurs, and there’s no way of telling for sure. Secondly, the assumption is that the frog had a similar jaw and muscle configuration to its living relatives. As such, these bite-force estimates should be taken with a grain of salt.

Still, it’s amazing to entertain the thought that somewhere, millions of years ago, frogs preyed on dinosaurs and not the other way around.

purple frog species

Adorable pig-nosed frog completely new to science found in India

An odd-looking frog that spends most its life underground and only comes outside when its ready to mate was recently discovered in India’s Western Ghats mountains. Its pointy snout, tiny eyes, and stumpy limbs might look funny but the truth is this is an extremely well-adapted creature to a life in the burrows.

purple frog species

Credit: JEGATH JANANI.

The frog is called Bhupathy’s purple frog (Nasikabatrachus bhupathi), in honor of Dr. Subramaniam Bhupathy, a well known Indian herpetologist who lost his life surveying the Western Ghats in 2014. Its appearance is characterized by a shiny purple coat, light blue rings around small eyes and a signature pig snout nose, according to researchers at the Centre for Cellular and Molecular Biology (CCMB) in Hyderabad.

With its long, fluted tongue, the frog gobbles up insects that live underground like termites and ants. Rarely does it leave the safety of the underground unless it rains during the monsoon season. This is the time for mating, as evidenced by the loud calls male Bhupathy’s purple frog bellow from under the sand in mountain streams.

In the same streams, the males court and mate with females, which deposit the fertilized eggs. Within a day or two, these are already ready to hatch into tadpoles. But even in this early life stage, the purple frogs are odd.

The tadpoles have sucker-fish like mouths which they use to cling to rocks behind waterfalls like leeches. Suspended from the wet rocks, the tadpoles can spend up to 120 days in the torrent which is the longest the species ever stays above ground during its whole lifespan. Once they’ve completed their transformation, the purple frogs ready themselves for a solitary subterranean existence, the authors reported in the journal Alytes. 

The findings are even more interesting once you realize this is only the second species in its family. The first is another purple frog described in 2003. Both species are very distant from their closest relatives, which live in Seychelles, likely because they had to evolve independently for millions of years.

“We confirmed it was a different species when we bar-coded its DNA and found that genetically it was very different from the Purple frog,” says Ramesh K Aggarwal, chief scientist at the CCMB and one of the five co-authors

This can only be yet another example of continental drift. About 65 million years ago, the Indian subcontinent was part of the ancient landmass of Gondwana before it split away from Seychelles.

If anything, this cute purple frog gives to show just how little we know about frogs or amphibians in general. There’s a whole world of unknown creatures out there and we can only rejoice at the opportunity to learn more about them on a daily basis.

The amazing see-through frog. Credit: Jaime Culebras.

Incredible new Amazon glass frog is so transparent you can see its beating heart

Deep in the Amazonian lowlands, biologists stumbled across a peculiar glass frog species completely new to science. What makes glass frogs so interesting, unique even, is their chest which varies in different levels of transparency. This trait is so pronounced in some individuals that you can see their beating hearts straight through the limpid chest. Unfortunately, the new species called Hyalinobatrachium yaku may already be threatened with extinction by oil exploitations in the area.

The amazing see-through frog. Credit: Jaime Culebras.

The amazing see-through frog. Credit: Jaime Culebras.

Glass frog or “see-through frog” is a unique type of frog that is named that way because of its translucent skin. These usually live in Central and South America, preferring tropical rainforests where they rest high in the treetops right above the water. These unique amphibians are usually tiny, typically 0.78 inches long, though some can reach 3 inches in length.

The body of the frog is usually bright green or olive green in color, and it’s the belly that’s covered in transparent skin. Liver, heart, and intestines can be seen when the glass frog is looked from the underneath.

Glass frogs are arboreal animals, meaning they spend most of their lives in trees and will come to the ground only during the mating season which takes place right after the rainy season. Females lay 20 to 30 eggs on the underside of leaves that hang right above the water. Males, on the other hand, guard the eggs until these are ready to hatch and fall on the below water stream. The males are also very protective of their mates’ eggs and will watch them 24/7. Nothing will sway the males from their jobs and no intrududer is intimidating enough for them. Some males have even been known to kick away wasps that get too close to the egg cluster!

More than 60 different species of glass frogs are known to science, the latest being Hyalinobatrachium yaku which was identified as unique by researchers at the Universidad San Francisco de Quito, in Ecuador. The team led by biologist Juan Guayasamin performed DNA sequencing on samples taken from the glass frog and found the genome didn’t match other species. They also found that the dark green spots on its back, its call, and reproductive behavior were different from other known frogs.

A juvenile H. yaku, stands out with its dark green spots and atypical reproductive behaviours.

A juvenile H. yaku, stands out with its dark green spots and atypical reproductive behaviours.

‘All species in this genus have a completely transparent ventral peritoneum, which means that organs are fully visible in ventral view,’ researchers explain in a new paper, published to ZooKeys.

‘The reproductive behaviour is also unusual, with males calling from the underside of leaves and providing parental care to egg clutches.’

Nobody’s sure why the see-through skin appeared in glass frogs but the discovery of H. yaku might help shed light in the matter. The more members scientists can draw on a family tree, the easier it becomes to identify out evolutionary traits and mechanisms.

Might be already endangered

All in all, Hyalinobatrachium yaku looks like a fine addition to the 100 to 200 of so new amphibian species discovered each year — far more than new birds or mammals. However, this joy might be short-lived. Like other glass frogs, this amphibian needs pristine streams to breed but these are beginning to dry up or get polluted from nearby oil wells.

“For example, even though a high proportion of the Ecuadorian Amazon is already concessioned to several extractive activities, the Government of Ecuador is planning to intensify oil extraction in the region,” the researchers wrote.

“Aside from obvious concerns such as water pollution, extraction of natural resources increased the level of regional road development, which could threaten populations of H. yaku.”

 

 

This YouTube time-lapse of cellular division in action will have you hitting replay again and again

We’ve often talked about cellular multiplication or division, but have you actually ever seen it in action? Well, through the magic of modern technology and the cinematic flair of YouTuber francischeefilms, you’re about to have a front-row seat to the show.

Their time-lapse video shows a Rana temporaria / common frog tadpole egg on its journey from a humble four cells to several million, all in just 20 seconds.

That’s much faster than in real life. According to francischeefilms, the video took “about 33 hours at 15-17C approximately” to make.

“The whole microscope sits on anti-vibration table. [I]t doesn’t matter too much what microscope people use to perform this,” francischeefilms further explains on their YouTube page.

“There are countless other variables involved in performing this tricky shot, such as: the ambient temperature during shooting; the time at which the eggs were collected; the handling skills of the operator; the type of water used; lenses; quality of camera etc.”

The YouTuber had to design and put together his own equipment to capture these incredible shots, as well as get the lighting and microscope set-up exactly right.

But all that hard work certainly paid off — seeing a life just starting out with such enthusiasm is nothing short of amazing. So the next time division comes into discussion, you’ll know exactly what it looks like.

 

Frog spit is one of the stickiest things you can find

New research showed that frog saliva is tailor-made to catch bugs. It’s sticky and perfectly designed to keep frog prey on its tongue and it could lead to creating better adhesives.

Frog attack captured using high-speed photography. Image credits: Alexis Noel et al, 2017.

Frogs snatch prey out of the air at incredible speeds, hanging on to them with only their tongues. Researchers have been wondering for quite a while how the frog manages to do that without losing hold of the bugs and now they’ve found the answer: it’s a combination of unique reversible saliva in combination with a super soft tongue.

To prove this, researchers from George Tech had to go through a pretty gross process — collecting frog saliva.

“I actually got 15 frogs, and scraped their tongues for a couple of hours one night,” says Alexis Noel, a PhD student at the Georgia Institute of Technology who led the study, “It was pretty disgusting.”

But at the end of the day, it was all worth it. Using high-speed photography and an instrument called a Rheometer to analyze frog saliva, they found that when reaches the prey, the saliva suddenly changes properties. Initially, the saliva is thick like honey, but with the force of impact, it liquefies and spreads over the entire insect. Then, it solidifies again trapping the poor creature so that it can be pulled towards the frog.

A similar phenomenon happens to paint. It’s fairly thick when it’s in the can, but becomes much smoother as you apply it to the brush. Then, as you apply it to the wall (or whatever you’re painting on), it becomes sticky again, sticking to the surface. Unlike water or honey, the paint’s (and the frog’s saliva) changes its viscosity with shear rate. This is what is called a non-Newtonian fluid.

The highly flexible and powerful tongue makes all of this possible.

“The tongue acts like a bungee cord once it latches onto its prey,” Alexis Noel added. “It deforms itself as it pulls back toward the mouth, continually storing the intense applied forces in its stretchy tissue and dissipating them in its internal damping.”

Frog attack captured using high-speed photography. Image credits: Alexis Noel et al, 2017.

Yet one question still remained — how does the frog take its prey off of the super-sticky tongue? Well, using its eyeballs of course. They force their eyeballs onto their tongue, liquefying the saliva once again.

“They actually bring their eyeballs into their mouth cavity and push down on the insect against the tongue,” Noel says.

David Hu, a professor in the George W. Woodruff School of Mechanical Engineering, is Noel’s advisor. He believes that this frog study could help engineers develop better adhesives.

“Most adhesives that have been created are stiff, especially tape,” said Hu, who is also a faculty member in the School of Biological Sciences. “Frog tongues can attach and reattach with soft, special properties that are extremely stickier than typical materials. Perhaps this technology could be used for new Band-Aids. Or it could be used to create new materials in soft manufacturing.”

The study, “Frogs use a viscoelastic tongue and non-Newtonian saliva to catch prey,” is published in the Journal of the Royal Society Interface.

Females are not rational when it comes to choosing their mates – at least in frogs

Picking a mate is one of the most important decisions anyone (human or animal) makes in a lifetime, so it’s important to weigh all the pros and cons and make a rational decision. But that doesn’t go for frogs. Female túngara frogs often exhibit irrational behavior when choosing a mate. This challenges many previously held beliefs as well as several biological behavior models.

The Tungara Frog females sometimes make irrational decisions when it comes to mating. Image via Wikipedia.

If you live in central America, the odds are you’ve seen (or at the very least, heard) túngara frogs, as they can live everywhere from thick forests to urban puddles. They’re only 2 cm long, but they can be very loud – the males use these loud calls to lure mates. Amanda M. Lea and Michael J. Ryan, two behavioral biologists working at the University of Texas (Ryan lab), studied their calls in detail to see what turns females on. They found that there’s a specific type of call they prefer.

“They tend to like longer calls. They also like lower-frequency calls,” says Lea. “Then, the other thing that’s a really big one for these gals is the ‘call rate.’ They love faster call rates. The faster a male can call, the better.”

But that’s only a general rule, and in real life, love calls can be very complicated. So they set up a controlled environment, in which females were placed in a room with some loudspeakers. From one speaker the scientists played a recording of frog call that had a really fast rate, but other features in its voice were less attractive. They then played another call which was slower, but featured other attractive features. In other words, they made the females choose between two “grey” options.

“They have two traits to evaluate,” Lea explains. “They have the call rate and they have the attractiveness of the call.”

The females consistently chose the fast guy, crawling repeatedly towards that speaker. But then, scientists added a third option: a call just like the slow, rejected one, except this one was much slower. The two other calls remained unchanged. What happened was surprising.

The females didn’t chose the third option, but its mere presence was enough to dissuade them from their original choice, rejecting the fast guy, and now choosing the slower one. The other, least attractive call, made the unattractive option seem more attractive.

“They actually switch their preferences,” says Lea. “So now call rate is no longer the most important thing.”

This is irrational and makes no sense – an option that should have no impact on anything actually makes females change their primary mating option; so far, there’s no explanation for that. The most unattractive guys just act as decoys.

“This is the first time we’ve found evidence for irrational mating behavior,” says Lea. “If they aren’t making rational decisions, then these [behavioral] models don’t hold up.”

So think about it guys, if you’re unattractive and want to pick up some girls, just have a more unattractive wingman. That has to work – at least if you’re a frog.

Journal Reference: Amanda M. Lea, Michael J. Ryan. Irrationality in mate choice revealed by túngara frogs. DOI: 10.1126/science.aab2012

First species of venomous frog found in Brazil

The first venomous (yes, venomous – not poisonous) frog was discovered in Brazil by mistake. A frog head-butted Carlos Jared in the hand, and after a while he started feeling a strange pain; it took him a while to connect the dots and realize that the frog was responsible for the pain he was feeling and decided to find out what he was dealing with.

venomous frog

A closeup of C. greeningi frog skin that reveals the spikes on its head. Image credits: Carlos Jared.

‘Venomous’ and ‘poisonous’ are sometimes used interchangeably, but they are different terms. Some frogs are poisonous when eaten and even when touched, but they don’t have a delivery mechanism – in other words, they’re not really venomous. Also, frogs have no fangs (like snakes do), so delivering venom would be quite difficult for them. However, two species of frog in Brazil have been found to be capable of injecting poison using horns on their head. They charge on their opponent and headbutt them, injecting the venom through the horns. This was not only surprising, but raised significant questions about animal toxicology. The study that describes the species writes:

“These frogs have well-developed delivery mechanisms, utilising bony spines on the skull that pierce the skin in areas with concentrations of glands,” the study said. “Because even tiny amounts of these secretions introduced into a wound caused by the head spines could be dangerous, these frogs are capable of using their skin toxins as venoms against their would-be predators.”

Edmund Brodie of Utah State University in the United States explains:

“Discovering a truly venomous frog is nothing any of us expected and finding frogs with skin secretions more venomous than those of the deadly pit vipers … was astounding,” Dr Brodie said.

Jared, now at the Butantan Institute in São Paulo, had to investigate the frogs under a microscope to realize how this mechanism works. Basically, bone spikes erupt near the venom glands, and as the frog’s lips curl back, the glands dribble the venom onto the spikes sticking out of the skull. Then, it’s simply a matter of poking the spikes against the foe.

venomous frog

Corythomantis greeningi frogs carry potent venom in their pouts. (Carlos Jared)

“This is very, very cool. Unprecedented would actually be an understatement,” says Bryan Fry, a molecular biologist at the University of Queensland who was not affiliated with the study. But if we already knew frogs could be poisonous, why is this discovery such a big deal? The answer lies in the often-misunderstood difference between poison and venom.

The venomous traits of the two species, Corythomantis greeningi and Aparasphenodon brunoi actually have a very strong venom; pound per pound, it’s almost twice as dangerous to mammals as typical venom of the fearedBothrops pit vipers, scientists explain. Tests have shown that one gram is capable of killing more than 300 000 mice or about 80 people. However, they produce it in much smaller quantities.

“It is unlikely that a frog of this species produces this much toxin and only very small amounts would be transferred by the spines into a wound. Regardless, we have been unwilling to test this by allowing a frog to jab us with its spines,” Dr Brodie said.

Finding this species shows just how much we still have to learn about animal toxins and venom. Venoms have popped up some 30 times in the tree of life, usually from usual enzymes. For example, spider venom originated from a harmless hormone—the spider version of insulin. Over time, evolution favors individual with more potent venoms. But in the case of the frogs, this came as a complete surprise.

“Even the most recent book on Brazilian frogs lists them as nontoxic,” says study co-author Edmund Brodie.

Journal Reference.

Scientists find “punk” shape shifting frog

For the first time, researchers have discovered a vertebrate able to change the texture of its skin from smooth to spiny. The new frog species was found in Ecuador in the plentiful moss surrounding the native forest.

frog

When researcher Katherine Krynak and her husband Tim spotted what seemed to be a new species of frog, they put it in a cup to study it the next morning. But when they returned, they observed something unexpected: the frog turned all punk, changing its skin from smooth to spiky. But it got even stranger: as they placed it on a napkin to take some photos, the skin smoothened up again.

“I then put the frog back in the cup and added some moss,” says Katherine, a PhD student at Case Western Reserve University in Ohio. “The spines came back… we simply couldn’t believe our eyes, our frog changed skin texture! I put the frog back on the smooth white background [and] its skin became smooth.”

According to their research, which was published in The Zoological Journal of the Linnean Society, the scientists discovered that a related species of frog could change its skin in a similar manner, raising further questions about how this trait evolved.

“Either these two different species from two different clades evolved the same trait, or all species had it and then lost the trait, or other species in this clade do this, too, and it’s just never been documented,” Dr. Krynak said.

There are obvious advantages to this – camouflage and avoiding predators. But while the camouflage part works really fine, it remains to be seen if this behavior actually scares off predators.

“The spines and coloration help them blend into mossy habitats, making it hard for us to see them,” said Katherine in a press releasefrom Case Western University. “But whether the texture really helps them elude predators still needs to be tested.” It’s also not clear how exactly mutabilis changes its skin texture.

Researchers will now work to determine how this happens.

 

Gardiners-Seychelles-frog

This frog hears through its mouth

One of the smallest amphibians in the world, the  Gardiner’s Seychelles frog, is also one of the most eccentric. The frog doesn’t stand out through an over-glamorous coloring or some unique, wild mating call, but rather as a result of one of its weird biological features. This frog doesn’t have ears – yet it can hear. How? By receiving sound waves through its mouth.

Gardiners-Seychelles-frogAll frogs actually hear in a different way from all the other animals, in the sense they don’t have  an external cartilaginous sounding board – instead frogs have eardrums placed directly under the skin. But Seychelles frogs don’t even have this. Can it hear in the first place? Well, a team of researchers from a variety of French universities tested the Seychelles hearing range. They placed a frog in a room where they played recorded calls from other frogs through a speaker. The frog responded to these calls, signifying it could hear them.

Talk with your ears, listen with your mouth

The mystery deepened even further after the scientists had the frogs X-rayed and saw that their bones didn’t conduct sound, like human jawbones do for instance. So scientists made a wild guess: what if the frog could hear through its mouth by directing sound to its inner ear – a cavity within the frog’s skull that hosts reverberated noises?They performed a simulation  and, indeed, it showed that the frog was indeed capable of hearing through this method. This doesn’t mean it hears in this manner though – it just demonstrates that it could.

The Seychelles frog can only be found on a few islands in the Seychelles, off the coast of Madagascar. Scientists suspect that due to its isolation, the species’ hearing has evolved very little. Advanced hearing, characterized by the evolution of eardrums, dates back from the time of  the separation of Gondwana, an ancient supercontinent. Studying Sechelles frogs, researchers hope not only to unravel how this peculiar animal performs basic biological functions, but also how Gondwana animals might had looked and behaved like.

via PopSci

 

The gastric brooding frog incubates and hatches its eggs in its gut. The hatchlings then exit through the frog's mouth. (c) Australian Government Department of the Environment, Water, Heritage and the Arts

Scientists resurrect extinct frog species that gives birth through its mouth

The gastric brooding frog incubates and hatches its eggs in its gut. The hatchlings then exit through the frog's mouth. (c) Australian Government Department of the Environment, Water, Heritage and the Arts

The gastric brooding frog incubates and hatches its eggs in its gut. The hatchlings then exit through the frog’s mouth. (c) Australian Government Department of the Environment, Water, Heritage and the Arts

In a great leap forward towards reviving extinct animal species, scientists at University of New South Wales, Australia have grown embryos that contain the genetic markup of a rather peculiar, yet unfortunately extinct frog species native to Australia. The frog died off in the 1980s due to parasites, loss of habitat, invasive weeds and fungus, and was one of the few animals known in the world to give birth through its mouth.

Birth through its mouth? Well, we’ve heard of weirder uses of the oral cavity, like urinating, but the gastric-brooding frog’s breeding trick is quite nifty. When this frog used to lay eggs, these were coated in a substance called prostaglandin, which breaks off the gastric acid in the stomach, making it a hospitable place for just about anything, including eggs. Naturally, the frog swallows these eggs, incubates them directly in the gut and when they hatch, the little baby frogs crawl out through the mouth.

Alas, both subspecies of frog – the the northern and souther gastric-brooding frog – went extinct sometime in the mid ’80s, yet genetics is not keen of farewells. Aptly named the Lazarus project, scientists have inserted dead genetic material of the extinct amphibian (conveniently, frozen specimens were kept in a common household freezer) into the donor eggs of another related species of living frog  – the great barred frog, which also lives in Queensland.

“In the beginning, the single cell eggs just sat there. But then, all of a sudden, one of the cells divided, and then it divided again, and again,” said University of NSW palaeontologist Mike Archer.

“There were a lot of high fives around the laboratory at that point.”

Resurrecting  the extinct back to life

The eggs continued to grow into three-day-old embryos, which scientists refer to as blastulas. They didn’t survive afterwards, unfortunately,  it was confirmed however that these embryos contain genetic information from the gastric-brooding frog. Still, their findings mark a big step forward in research efforts directed towards riving extinct animals. The Newcastle researchers are confident that this is a purely technical, not biological problem and in future attempts they’ll be able to breed a gastric-brooding frog to adulthood.

“This is the first time this technique has been achieved for an extinct species,” conservation biologist Michael Mahony told the Sydney Morning Herald.

The researchers hope that someday they’ll be able to revive a slew of currently extinct species  – a flicker of hope that humanity’s monstrous mistakes might be mended –  such as the woolly mammoth, dodo, Cuban red macaw and New Zealand’s giant moa.

“We are watching Lazarus arise from the dead, step by exciting step,” says the leader of the Lazarus Project team, Professor Mike Archer, of the University of New South Wales, Sydney. “We’ve reactivated dead cells into living ones and revived the extinct frog’s genome in the process. Now we have fresh cryo-preserved cells of the extinct frog to use in future cloning experiments.

“We’re increasingly confident that the hurdles ahead are technological and not biological and that we will succeed. Importantly, we’ve demonstrated already the great promise this technology has as a conservation tool when hundreds of the world’s amphibian species are in catastrophic decline.”

Professor Archer spoke last week at the TEDx DeExtinction event  when the Lazarus Project was publicly discussed for the first time. Archer also expressed his ongoing interest in cloning the extinct Tasmanian tiger, which died off almost a century ago.