Frogs’ fluorescence, why?


This video says about itself:

17 March 2017

A group of Argentine and Brazilian researchers has discovered the first case of natural fluorescence in amphibians, in a species of tree frog that is frequently found in South America.

From Science News:

First fluorescent frogs might see each others’ glow

Natural Day-Glo may play a role in amphibian’s fights and flirtations

By Susan Milius

10:00am, April 3, 2017

Could fluorescence matter to a frog? Carlos Taboada wondered. They don’t have bedroom black lights, but their glow may still be about the night moves.

Taboada’s question is new to herpetology. No one had shown fluorescence in amphibians, or in any land vertebrate except parrots, until he and colleagues recently tested South American polka dot tree frogs. Under white light, male and female Hypsiboas punctatus frogs have translucent skin speckled with dark dots. But when the researchers spotlighted the frogs with an ultraviolet flashlight, the animals glowed blue-green. The intensity of the glow was “shocking,” says Taboada of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” in Buenos Aires.

And it is true fluorescence. Compounds in the frogs’ skin and lymph absorb the energy of shorter UV wavelengths and release it in longer wavelengths, the researchers report online March 13 in Proceedings of the National Academy of Sciences. But why bother, without a black bulb? Based on what he knows about a related tree frog’s vision, Taboada suggests that faint nocturnal light is enough to make the frogs more visible to their own kind. When twilight or moonlight reflects from their skin, the fluorescence accounts for 18 to 30 percent of light emanating from the frog, the researchers calculate.

Polka dot frogs, common in the Amazon Basin, have plenty to see in the tangled greenery where they breed. Males stake out multilevel territories in vast floating tangles of water hyacinths and other aquatic plants. When a territory holder spots a poaching male, frog grappling and wrestling ensues. Taboada can identify a distinctive short treble bleat “like the cry of a baby,” he says, indicating a frog fight.

Males discovering a female give a different call, which Taboada could not be coaxed to imitate over Skype. The polka dot frogs’ courtship is “complex and beautiful,” he says. For instance, a male has two kinds of secretion glands on the head and throat. During an embrace, he nudges and presses his alluring throat close to a female’s nose. If she breaks off the encounter, he goes back to clambering in rough figure eights among his hyacinths, patrolling for perhaps the blue-green ghost of another chance.

Glass frogs’ parental care, new research


This video says about itself:

Just a few hours of motherly attention help glass frog eggs survive | Science News

31 March 2017

Guarding her eggs, a glass frog stays with the brood despite annoying finger prods from scientists. This species provides the only prolonged maternal care yet found among glass frogs, but even short-term moms stayed on duty when researchers poked at them. Read more here.

Credit: Jesse Delia/Boston University

Moor frogs’ mating season


This 31 March 2017 video from the Netherlands is about the moor frogsmating season. Then, male moor frogs get a blue colour.

World’s first fluorescent frog discovered in Argentina


This video says about itself:

14 March 2017

World’s first fluorescent frog that glows bright green is found in Argentina

Under normal light the polka-dot tree frog is a dull green/brown colour.

But scientists stumbled upon the species’ rare ability under their UV torches.

It is rare for land animals to have fluorescent skin pigments.

The pigments absorb light and re-emit it at longer wavelengths.

Read more here.

See also here.

Scientific description of this new discovery about Hypsiboas punctatus frogs: here.

‘Extinct’ frog rediscovered in Zimbabwe


Cave squeaker frog, photo by Francois Becker

By Dominique Mosbergen, Reporter, The Huffington Post:

Tiny Frog Last Seen In 1962 Found In The Mountains Of Zimbabwe

Scientists were thrilled to find the inch-long “cave squeaker” alive and well.

02/07/2017 10:21 am ET

Francois Becker knows his frog calls ― and he knows them well. But in early December, while conducting research near the summit of a remote mountain in eastern Zimbabwe, the ecologist heard a call he could not quite place.

“When I first heard [it], I thought it might be an insect,” Becker, a graduate student at the University of Cape Town, told The Huffington Post over email on Monday. “It was a soft, high-pitched whistle repeated several times.”

But as he got closer to the sound, Becker determined that it wasn’t an insect at all. “The ‘texture’ of the call, for lack of a better word, confirmed that it was probably a frog,” he said. Specifically, a kind of Arthroleptis frog.

Arthroleptis is a genus of frogs endemic to tropical sub-Saharan Africa. They’re known for their high-pitched whistling calls and tiny stature (the largest species of the genus, Arthroleptis tanneri, grows to just two inches long). They are also direct breeders, meaning they ― unlike most other frogs — are born as fully formed froglets and not as tadpoles.

“Francois had done a great deal of work on [Arthroleptis frogs] in South Africa, and had paid particular attention to their calls,” Becker’s research colleague, Robert Hopkins, told The Zimbabwean in an interview last month. “He heard a call which he recognized as that of an Arthroleptis, but did not or could not identify it, so he tracked that call and ultimately found the first specimen.”

The source of the unusual whistle turned out to be an unimaginable treasure: a rare cave-dwelling frog that had not been seen in over 50 years.

This is Arthroleptis troglodytes, also known as a “cave squeaker.” Becker took the first photos of the species ever.

The cave squeaker was last spotted in the rocky Chimanimani mountains of eastern Zimbabwe in 1962, the year it was first discovered. The minuscule animal measures no more than an inch long, and scientists assumed it was extinct after several unsuccessful searches, including a 2010 expedition.

Hopkins, a 75-year-old researcher with Zimbabwe’s Natural History Museum, had been searching for the frog since 1998, to no avail.

In a last-ditch attempt to find the elusive animal, he applied for a grant from the Mohamed bin Zayed Species Conservation Fund last year to conduct another search. He roped in Becker and a Zimbabwean entomologist named Scott Herbst. In December, the group headed to the mountains of Chimanimani, the only place the frog was known to exist.

Hopkins, who has cancer, was not able to participate in the search effort due to his age and illness, he explained in a research report. So he was in Chimanimani village on Dec. 2 when he received a phone call from a “very excited” Becker.

“[H]e had located an Arthroleptis troglodytes,” wrote Hopkins in the report. “It was great surprise and release after all these years.”

Remarkably, Becker didn’t just find one lonesome cave squeaker that day, but several.

He said it had taken him about 45 minutes to track down the first frog after hearing its call. “I was so excited when I saw it that my hands were shaking, and I let it slip away,” he recalled. “It hopped into a deep crevice and I could no longer see it. However, by this time I had recorded the call and was playing it back to them, to prompt other nearby males to start calling. It took me about another 40 minutes to find the next one.”

Becker and his team, which also included two local guides, collected three males and one female that day.

Hopkins said they gathered a “great deal of data,” including DNA samples that have been sent for analysis. Hopkins said the cave squeakers appear to be “breeding well” in the Chimanimani mountains.

There seems to be a very viable population,” he wrote in the report. The exact number of frogs, however, remains unknown.

Scientists are now considering conservation strategies for the frog species. Hopkins told The Zimbabwean that he, together with the Zimbabwe Parks and Wildlife Management Authority, are mulling over the possibility of breeding cave squeakers in his laboratory and releasing them back into the wild.

Hopkins worries that the recent discovery will prompt people to illegally capture and export cave squeakers from Chimanimani. A Parks Authority spokeswoman told The Associated Press this week that experts are devising a management plan to protect the animal. 

“We are expecting an influx of scientists looking for it,” said Caroline Washaya-Moyo. “We will do everything in our power to protect and conserve the frog.”

Amphibians, including frogs, are one of the most threatened groups of animals on the planet. According to the International Union for Conservation of Nature, about 1 in 3 amphibians face the threat of extinction. Climate change, habitat destruction and disease are some of the greatest threats facing frogs and other amphibians.

A 2011 study found that amphibians may not be evolving fast enough to deal with the “enormous” human-induced changes to the environment over the past 100 years.

“With a permeable skin and exposure to both aquatic and terrestrial problems, amphibians face a double whammy,” zoologist Andrew Blaustein, co-author of the study, told LiveScience at the time. “Because of this, mammals, fish and birds have not [yet] experienced population impacts as severely as amphibians.”

World Frog Day

Frogs’ tongues, new research


This video says about itself:

How are frog tongues so sticky? | Science News

1 February 2017

Here’s what puts the grip in a frog’s high-speed strike: quick-change saliva and a tongue softer than a marshmallow.

From Science News:

What gives frog tongues the gift of grab

Quick-switch saliva, squishy tissue combine to catch prey

By Susan Milius

7:05pm, January 31, 2017

Frogs’ remarkable power to tongue-grab prey — some as big as mice or as oddly shaped as tarantulas — stems from a combo of peculiar saliva and a supersquishy tongue.

The first detailed analysis of the stickiness of frog saliva shows that the fluid can shift rather abruptly from gooey to runny, says mechanical engineer Alexis Noel of Georgia Tech in Atlanta. Those quick changes come in handy during the various phases of a single tongue strike. And it all works because the tongue itself is so soft, Noel and colleagues report February 1 in Journal of the Royal Society Interface.

Internet videos of frogs feasting sparked Noel’s curiosity about their ability “to eat furry things, hairy things, slimy things,” she says, and to do so with speed and power. A frog tongue strikes five times more quickly than a human can blink.

But frog tongue tissue is so soft that none of the standard equipment on campus could measure it without special modifications. Noel eventually discovered that this tissue is as soft as a brain, which is itself naturally softer than a marshmallow.

When the tongue shoots out at, say, a fly, the soft frog tissue splats on impact, spreading and curling around the prey. This action “massively increases the contact area” of frog tissue that can stick to the fly, enhancing grip, Noel says. Then frog saliva intensifies the effect.

Frogs don’t have salivary glands spread around inside their mouths that drip saliva on their tongues. Instead, the tongue itself secretes the saliva. To see how sticky frog saliva might be, Noel spent several hours per sample scraping some 15 frog tongues to put together enough spit for a single test.

Noel and colleagues found that this saliva is what’s called a shear-thinning liquid, which grows thinner and easier to stir or smear around when force is applied. Smacking into a fly jolts saliva from its sticky phase — more viscous than honey, she says — into the more “liquidy” phase “flowing into all the small cracks” of the insect body. As the tongue returns to the mouth, the spit thickens again, intensifying the grip.

During that tongue jerk, acceleration can surge to 12 times the pull of Earth’s gravity. Still, in spite of the spit’s stickiness, the insect could be flung loose at this point, Noel calculated. But the soft stretchiness of the tongue, a natural bungee cord that retracts without too much of a jolt, prevents the loss, she says.

But once the fly is in the mouth, the tongue’s grip needs to loosen so the fly can slide down the gullet. “Frogs actually use their eyeballs while swallowing,” Noel says. Eyeballs sink from bulges to barely bumps, dipping inside the head and pushing food back toward the throat. The eyes’ impact jars the saliva into a runnier phase, easing its grip on the prey.

Frogs aren’t the only hunters that tongue-snatch their prey. Chameleon tongues also can be very sticky, says Pascal Damman, who studies the physics of soft matter (including chameleon tongues) at the University of Mons in Belgium. The new findings remind him of how chameleons catch prey using gooey mucus and a stretchy tongue, he says.

New frog species discovery in India


This video from India says about itself:

Euphlyctis karaavali: CR Naik

25 December 2016

Video clip of Karaavali skittering frog. This is part of supplementary video clip of the article published in Asian Herpetological Research 2016, 7(4): 229–241; DOI: 10.16373/j.cnki.ahr.160020

From BirdLife:

The frog we thought was a kingfisher

By Tim Knight, 24 Jan 2017

A coastal survey in western India has spawned the discovery of a new species hiding in plain sight.

Tadpoles turning into frogs are nothing new, but when a bird is miraculously transformed into an amphibian – and a previously unknown one at that – it’s time to sit up and take notice. In a bizarre turn of events that gives a whole new meaning to the term ‘metamorphosis’, a frog whose call was initially mistaken for the more familiar sound made by a white-throated kingfisher has just been confirmed as a new species.

It was citizen science that first shed light on the true identity of the Karaavali skittering frog, named after the region where it was first recorded. In the local Kannada language widely spoken in the state of Karnataka, Karaavali is the name for India’s west coast.

A local forester, C R Naik, was monitoring the biodiversity around his coastal village in order to document the bird, snake and frog species in the vicinity. Having realised that the kingfisher-like call was actually being emitted by a frog, he had the presence of mind to record it on his mobile phone. During subsequent fieldwork in the Western Ghats he played back the recording to a team of scientists, including several herpetologists, who naturally assumed that they were listening to a bird.

Leap of the imagination

Among them was Seshadri K S, winner of a 2010 Conservation Leadership Programme (CLP) award who is currently studying for a PhD at the National University of Singapore. Intrigued by Naik’s claim that the call belonged to a frog and not, in fact, to the commonly heard White-throated Kingfisher Halcyon gularis, Seshadri resolved to visit the coastal site and investigate the mystery for himself. Sure enough, a few hours of nocturnal detective work amid flooded paddy fields in the company of Naik revealed that the forester’s story was not an elaborate hoax. Subsequent analysis of the call helped to confirm that the species was indeed new to science.

“Often, such scientific discoveries happen because there are foot soldiers like Mr Naik working hard in the field”, Seshadri observed. “Him being a forest official and making observations on nature makes this discovery special. We hope this discovery will inspire the staff of the forest departments and research is encouraged. By joining hands with researchers, Naik has come to the forefront of biodiversity conservation. Such efforts will [help to put] biological research in India on a par with [the rest] of the world.”

In a wonderful example of the results that can be achieved when enthusiastic and knowledgeable citizens join forces with experts, Naik is among the co-authors of a paper recently published in the December 2016 issue of Asian Herpetological Research, which brought the Karaavali skittering frog discovery to the attention of the wider scientific community.

Public engagement

Dr Gururaj K V, a renowned frog researcher and another co-author of the recent paper, who performed the bioacoustics analysis of the call, is a strong advocate of the need to engage the general public in scientific pursuits and was therefore particularly gratified that citizen science had played such a key role in the discovery: “We were certain that the call was of a bird and [that] he was taking us for a ride; however, Mr Naik was adamant. We conceded that the call ought to be explored more and asked Naik to make a video next time he heard it. He immediately got to work and sent us short video clips and said this was a new species of frog.”

Naik himself was equally elated: “I am so happy that a new frog [has been] discovered from my native place and I am doubly delighted to be part of this discovery. I am thankful for the entire team of scientists who took trusted in me. This discovery has motivated me and I will continue making observations, not only about frogs, but in other [areas of] natural history. Such observations can help in creating awareness among citizens about nature.”

The newly discovered species is already threatened by nearby infrastructure development in the shape of highway construction and conversion of agricultural land. The paper’s authors highlight the fact that the frog appears to be restricted to just three districts in the coastal plains of Karnataka, and recommend that it should be officially classified as Endangered on the IUCN Red List.

See also here.