Dinosaur age and modern frog discoveries


This 14 June 2018 video says about itself:

Frogs trapped in amber for 99 million years are giving a glimpse of a lost world. The tiny creatures have been preserved in sticky tree resin from the later part of the Age of the Dinosaurs.

From the Florida Museum of Natural History in the USA:

Amber fossils provide oldest evidence of frogs in wet, tropical forests

June 14, 2018

Summary: 99-million-year-old amber fossils from Myanmar provide the earliest evidence of frogs in wet, tropical forests.

About 99 million years ago, a tiny juvenile frog in present-day Myanmar was suddenly trapped in sap with a beetle, perhaps its intended next meal.

Unlucky for the frog, but lucky for science.

An extinct species now named Electrorana limoae, it’s one of four fossils that provide the earliest direct evidence of frogs living in wet, tropical forests and are the oldest-known examples of frogs preserved in amber.

“It’s almost unheard of to get a fossil frog from this time period that is small, has preservation of small bones and is mostly three-dimensional. This is pretty special,” said David Blackburn, study co-author and the associate curator of herpetology at the Florida Museum of Natural History. “But what’s most exciting about this animal is its context. 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.”

The findings and species description were published today in Nature’s Scientific Reports.

Frogs have been around for at least 200 million years, but glimpsing their early heyday is tough. Often small and lightly built, frogs don’t tend to preserve well. The frog fossil record skews toward more robust species from arid, seasonal environments, although the bulk of frog diversity today lives in tropical forests.

“Ask any kid what lives in a rainforest, and frogs are on the list”, Blackburn said. “But surprisingly, we have almost nothing from the fossil record to say that’s a longstanding association.”

The amber deposits of northern Myanmar in Southeast Asia provide a unique record of ancient forest ecosystems, with fossil evidence of mosses, bamboo-like plants, aquatic spiders and velvet worms. The discovery of Electrorana and the other fossils, the first frogs to be recovered from these deposits, help add to our understanding of frogs in the Cretaceous period, showing they have inhabited wet, tropical forests for at least 99 million years.

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

Less than an inch long, Electrorana is the most well-preserved of the group. Clearly visible in the amber are the frog’s skull, its forelimbs, part of its backbone, a partial hind limb and the unidentified beetle. The other amber fossils contain two hands and an imprint of a frog that likely decayed inside the resin.

But Electrorana raises more questions than it answers, Blackburn said.

Many characteristics herpetologists use to discern details of a frog’s life history and determine how it’s related to other frogs — wrist bones, the pelvis, hip bones, the inner ear, the top of the backbone — are either missing or were not yet fully developed in the juvenile frog.

The existing bones provide clues about Electrorana’s possible living relatives, Blackburn said, but the results are puzzling: Species that have similar features include fire-bellied toads and midwife toads — Eurasian species that live in temperate, not tropical, ecosystems.

Gathering CT skeletal data for both living and extinct frogs, one of Blackburn’s long-term projects, could help illuminate ancient evolutionary relationships, possibly clarifying how Electrorana fits into the frog tree of life.

In the meantime, Blackburn nurtures the hope that other frogs in amber will be discovered, making Electrorana more than a one-hit wonder.

“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.”

In a new study, researchers have investigated how the endocrine-disrupting substance linuron affects reproduction in the West African clawed frog, Xenopus tropicalis. The scientists found that linuron, which is used as a pesticicide, impaired the males’ fertility, and that tadpoles developed ovaries instead of testicles to a greater extent, which caused a female-biased sex ratio: here.

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Poison dart frogs’ colours, also camouflage


This 2016 terrarium video says about itself:

Dendrobates tinctorius ‘Powder Blue’ Calling.

Male dart frog vocalizing while female (barely seen) climbs the glass attempting to get to him.

From the University of Bristol in England:

Bright warning colors on poison dart frogs also act as camouflage

June 4, 2018

Poison dart frogs are well known for their deadly toxins and bright colours, which have made them a classic example of warning coloration.

The Dyeing Dart Frog, for example, is highly toxic and warns its predators with a bright yellow-and-black pattern.

However, new research led by scientists at the University of Bristol has revealed that the colour pattern does more than simply signal “danger.” Counterintuitively, it also works as camouflage.

Lead author, Jim Barnett completed this research, published today in the journal Proceedings of the National Academy of Sciences, while studying for a PhD at Bristol. He is now based at McGill University in Canada.

He said: “Effective as warning signals are, it’s not necessarily the best strategy to be maximally conspicuous.

Certain predators have evolved tolerance of toxins that would be deadly for humans, and some individual predators may have not encountered the warning signal prey before (a dangerous mistake for the predator, but also for the frog).

“So, colour patterns that could be distinctive close-up, but work as camouflage from a distance, would provide a clear advantage.”

Combining fieldwork in the jungles of French Guiana, computational modelling, and laboratory visual search experiments, Barnett and colleagues from the University of Bristol’s School of Biological Sciences and the School of Experimental Psychology investigated how the Dyeing Dart Frog uses its colours to balance the benefits of effective warning signals with the advantages of concealment.

They found that, despite being highly conspicuous at close range, the particular colours and their arrangement allow the pattern to blend together to form background-matching camouflage when viewed from a distance.

The frog’s pattern, therefore, allows it to get the best of both worlds: high fidelity camouflage until a predator discovers it, at which point its bright, highly salient, warning signal becomes clear.

Co-author Professor Innes Cuthill from the University of Bristol added: “How many other animals use ‘distance-dependent coloration’ to balance competing evolutionary pressures is yet to be explored.

“Being able to signal when close to a would-be mate, whilst remaining inconspicuous to more distant predators would seem beneficial. So too for human applications such as military camouflage, where recognition by allies is as important as concealment from foes. Also, signage that only need be clear at the distance where the information is needed, but might be distracting if detected earlier.”

Tree frog wakes up, video


This April 2018 video is about a tree frog waking up near the Loonse en Drunense Duinen nature reserve in North Brabant province in the Netherlands.

Toby Bissels made this video.

Moor frogs gathering


This April 2018 video shows blueish male moor frogs gathering in Twente region in the Netherlands for the mating season.

Harry Brummelhuis made this video.

Mating common frogs video


This is a video about mating common frogs in Wageningen, the Netherlands.

Some Panamanian frogs recovering from epidemic


This video says about itself:

Frogs vs. Fungus | National Geographic

22 September 2009

Panama’s golden frog is a symbol of good luck and prosperity. Now researchers are fighting to save the rare amphibian from a naturally occuring – and deadly – fungus.

That was then. And now …

From Science, 30 March 2018:

Shifts in disease dynamics in a tropical amphibian assemblage are not due to pathogen attenuation

Resistance is not futile

The fungal disease chytridiomycosis has wreaked havoc on amphibians worldwide. The disease is caused by the organism Batrachochytrium dendrobatidis and was first identified in the late 1990s. Voyles et al. revisited protected areas in Panama where catastrophic amphibian losses were recorded a decade ago (see the Perspective by Collins). Although disease theory predicts that epidemics should result in reduced pathogenicity, they found no evidence for such a reduction. Despite this, the amphibian community is displaying signs of recovery—including some species presumed extinct after the outbreak. Increased host resistance may be responsible for this recovery.

Abstract

Infectious diseases rarely end in extinction. Yet the mechanisms that explain how epidemics subside are difficult to pinpoint. We investigated host-pathogen interactions after the emergence of a lethal fungal pathogen in a tropical amphibian assemblage. Some amphibian host species are recovering, but the pathogen is still present and is as pathogenic today as it was almost a decade ago. In addition, some species have defenses that are more effective now than they were before the epidemic. These results suggest that host recoveries are not caused by pathogen attenuation and may be due to shifts in host responses. Our findings provide insights into the mechanisms underlying disease transitions, which are increasingly important to understand in an era of emerging infectious diseases and unprecedented global pandemics.

See also here.

New frog species discovery in Indonesia


This video says about itself:

Borneo Eared Frog or Bony Headed Flying Frog – Polypedates otilophus

30 January 2014

This interesting frog species can be found in Borneo, Sumatra and other Indonesian islands. Read more about various frog species here. This frog has interesting shaped legs which give it the ability to glide. The flying frog of Borneo also has bony protrusions behind its eyes which give it the appearance of having ears. It is also sometimes called the File-eared tree frog. In this video I show a few different frogs. This was taken at a chorus of colors exhibit.

From ScienceDaily:

Life in the fast flow: Tadpoles of new species rely on ‘suction cups’ to keep up

The frogs living in the rainforest of Sumatra also represent a new genus

March 12, 2018

Summary: The young of two new species and a genus of frog found to inhabit Sumatra’s rainforests have developed a unique ability to latch onto rocks in the fast-flowing rivers, using bellies crafted by evolution into ‘suction cups’. Herpetologists use their remarkable discovery to highlight the unique biodiversity of the island, which is under imminent threat due to rampant habitat modification and deforestation.

Indonesia, a megadiverse country spanning over 17,000 islands located between Australia and mainland Asia, is home to more than 16% of the world’s known amphibian and reptile species, with almost half of the amphibians found nowhere else in the world. Unsurprisingly, biodiversity scientists have been feverishly discovering and describing fascinating new animals from the exotic island in recent years.

Such is the case of an international team from the University of Hamburg, Germany, University of Texas at Arlington, USA, University of Bern, Switzerland and Bandung Institute of Technology, Indonesia, who came across a curious tadpole while collecting amphibian larvae from fast-flowing streams as part of an arduous expedition in the remote forests on the island of Sumatra.

To the amazement of the scientists, it turned out that the tadpoles possess a peculiar cup-like structure on their bellies, in addition to the regular oral disk found in typical tadpoles. As a result, the team described two new species and a genus in the open access journal Zoosystematics and Evolution. A previously known, but misplaced in an unsuitable genus, frog was also added to the group, after it was proved that it takes advantage of the same modification.

“This phenomenon where tadpoles display ‘belly suckers’ is known as gastromyzophory and, albeit not unheard of, is a rare adaptation that is only found in certain toads in the Americas and frogs in Asia”, explains lead author Umilaela Arifin.

The abdominal sucker, it is hypothesized, helps these tadpoles to exploit a very special niche — fast-flowing streams — where the water would otherwise be too turbulent and rapid to hang around. Gastromyzophorous species, however, rely on the suction provided by their modified bellies to secure an exclusive access to plentiful food, such as algae, while the less adapted are simply washed away.

When the scientists took a closer look at the peculiar tadpoles and their adult forms, using a powerful combination of molecular and morphological data, they realized that they had not only stumbled upon a rare amphibian trait, but had also discovered two brand new species of frogs in the process.

Moreover, the animals turned out so distinct in their evolutionary makeup, compared to all other frogs, that the scientists had to create a whole new genus to accommodate them. Formally named Sumaterana, the genus is to be commonly referred to as Sumatran Cascade Frogs.

“We decided to call the new genus Sumaterana after Sumatra, to reflect the fact that these new species, with their rare evolutionary adaptation are endemic to Sumatra’s rainforests and, in a sense, are emblematic of the exceptional diversity of animals and plants on the island,” says co-author Dr. Utpal Smart. “Tragically, all of them are in peril today, given the current rate of deforestation.”

The authors agree that much more taxonomic work is still needed to determine and describe Sumatra’s herpetofaunal diversity, some of which they fear, could be irreversibly lost well before biologists have the chance to discover it.