marine reptiles

A ‘Mysterious’ New Frog Species With Hidden Spots and an Insect-Like Call

Discovered in the Western Ghats of southern India, the species is unique enough to be placed in a newly-created genus as well.

It was after a heavy spell of rain during the 2015 monsoon that Sonali Garg walked out to a spot she had been visiting regularly, and unsuccessfully, for more than two years. A large muddy puddle.

But this time, she struck gold in the form of a new species of frog, Mysticellus franki sp. nov., which turned out to be so unique the study authors have assigned it to a newly created genus.

It all started in 2013 when Garg encountered “strange looking” tadpoles in that muddy puddle when conducting amphibian surveys for her PhD from Delhi University. It was clear the tadpoles belonged to the frog family Microhylidae, but beyond that, “we couldn’t pinpoint what species the tadpoles belonged to,” said Garg in an interview with Mongabay.

When the researchers sequenced the tadpoles and examined the DNA, it was clear that the tadpoles were of a hitherto unknown frog species.

“We have a library of sequences of frogs and other amphibians from the country and we could compare the sequence of the unknown tadpole against them,” said Garg. “To our surprise, the sequence did not match any frog species from the country; it fell into the family [Microhylidae], but beyond that, it did not match anything that was known from India.”

With no knowledge about the adult frog — where it was found, whether it was big or small. Garg and her team started visiting the puddle where they collected the tadpoles regularly. An adult specimen was needed to carry out the necessary morphological analyses to delve into the mysterious new species.

“For the next two years, we kept going back to the same spot. It was the only spot we were sure we would get it,” said Garg. “So we went back there at different seasons and different times of the year because we didn’t know when this frog would come out.”

“Eventually, after two years of this exercise of repeated searching, one monsoon, a couple of days after the monsoon hit, when there was sufficient water that collected on the ground, around the puddles … we saw the frogs. They were there in the hundreds, it was magical. It was as if the frogs were welcoming us,” she added, the excitement still palpable in her voice even after nearly four years.

The new species “was an accidental discovery,” said Garg and supervisor S.D. Biju. “We just happened to be at the right place, at the right time. And of course, often we fail to look closely. In this case, we looked closely at every tadpole, and that’s how this discovery happened!”

Male and female specimens of the newly discovered Mysticellus franki sp. Credit: S.D. Biju

A new species … and a new genus

After making careful notes from the field and recording the calls of the male frogs serenading for females in the puddles, the researchers collected specimens and brought them to the lab to carry out genetic analyses.

A combination of genetic, morphological and call data threw up the final diagnosis. The frog was definitely a new species, and sufficiently different from other members of the family Microhylidae found in India to be assigned to its own genus as well.

The new species belongs to sub family Microhylinae. The genus name Mysticellus is derived from the Latin mysticus, meaning mysterious, and ellus, which means diminutive. The name highlights “the ability of this small frog to remain out of sight despite its occurrence in wayside areas surrounding human settlements,” write the authors in the paper. The species name franki honours Franky Bossyut, a professor and amphibian biologist at Vrije Universiteit Brussel.

“I agree with assignment of the species status. The allocation of a genus status is motivated based on molecular evidence. The evidence is still tenuous because we have one member of the new genus,” said Karthikeyan Vasudevan, senior principal scientist at the Laboratory for the Conservation of Endangered Species (LACONES), Centre for Cellular and Molecular Biology.

“More than anything, it is surprising that it has not been already found and described. While very similar in shape, size, and colouration to other microhylid frogs in southeast Asia, there is nothing in the Western Ghats of India that resembles this,” said David Blackburn, the Associate Curator of Amphibians and Reptiles at the Florida Museum of Natural History. “It is only the secretive nature of these frogs that has resulted in them only now being known to science.”

The new species of frog was discovered when researchers came across a ‘strange’ looking tadpole. After continuously searching for an adult for two years, they spotted around 100 adult frogs around a roadside puddle. Credit: S.D. Biju

Hidden spots and an insect-like call

The researchers observed that the frogs started congregating in hundreds around temporary muddy puddles, two to three days after the first monsoon showers. After four to five days of intense breeding, the frogs disappeared completely, leaving the researchers mystified.

“After we first discovered this frog in 2015, we carried out several surveys in and around the region over a period of three years to study this frog. However, due to its secretive behaviour we were only able to locate it during a very short window of less than four days,” said the authors in an interview.

After the frogs disappeared, the researchers were not able to locate “even a single individual” at any other time of the year. “We don’t know where it hides, lives, and what it does for the rest of the year. The frog’s external appearance does not show morphological adaptations for burrowing. At the same time, we doubt that it simply hides under leaf litter, rocks and stone (the usual hiding places for frogs during the non-breeding time). It’s still a mystery for us,” they said.

When the males called to attract females, they raised the hind part of the body to show off “a pair of black false-eye like spots.” The frogs did the same when the researchers tried to approach them, said Garg.

“The effect is quite startling,” she said. “When the animal is sitting down, the spots are hidden. When we were close to the animal, the frog raised the hind part of its body. This movement really made the spots very visible.”

“The best guess we have is that it’s a defensive mechanism,” she said.

The call of the frog is also quite distinct, observed the researchers. “It resembles an insect chorus,” write the authors in the press release.

The frogs probably had such a unique call to attract females in the most efficient manner, said Garg. “Even if a puddle is crowded with multiple frog species and multiple individuals of the same species, even if it’s pitch dark, the female needs to be able to find her way to the male,” she said. “This is one reason to have unique calls. Also, for this species, with such a short breeding window of four or five days, the pressure to get it right is much higher,” she added.

The frog has two distinct eye-like spots on its rear-end which probably serve as a self-defence feature. Credit: S.D. Biju

A mysterious past

A phylogeny (a sort of family tree) of all known genetic data known from the family Microhylidae shows that the closest relative of the subfamily Microhylinae is the subfamily Dyscophinae, which is restricted to Madagascar.

The available molecular evidence gives us this story. The family Microhylidae would have originated on Gondwanaland, the ancient supercontinent which would eventually break up to form most of South America, Africa, the Indian subcontinent, Australia and Antarctica. When Gondwanaland broke up, the subfamily Dyscophinae took up home in Madagascar and sub family Microhylinae moved on toward Asia on the Indian subcontinent. The split between Dyscophinae and Microhylinae happened about 67 million years ago, giving Microhylinae enough time to diversify in the Indian subcontinent as it drifted along towards Eurasia. Once the Indian subcontinent docked at Eurasia, frogs that make up the Microhylinae subfamily spread all over Asia.

For M. franki in particular, the closest relative on the family tree is the genus Micryletta, also belonging to subfamily Microhylinae but found in the Indo-Burma and Sunderland biodiversity hotspots in Southeast Asia and China.

Using algorithms that can parse out evolutionary timelines by considering the rate at which DNA changes over time, the researchers were able to give tentative dates to different nodes of the phylogeny.

The secretive frogs vanished after appearing for the breeding season which lasted for around four days. Credit: S.D. Biju

“Our study shows that the common ancestors of Mysticellus and Micryletta diverged about 40 million ago. Most likely they originally inhabited the Indian Peninsula and later diverged to give rise to both these genera,” said the authors.
The authors posit that the two genera are likely to have split when the Indian landmass moved close to mainland Southeast Asia through the Myanmar-Malay Peninsula during Middle/Late Eocene.

Karthikeyan Vasudevan from LACONES said, “Recent evidence from the study of arthropods in amber suggests that prior to the final collision at around 55 million years ago with Asia, India moved close to or had land connections with Africa and Europe.” Some models of continental drift show that species could have moved between the Indian subcontinent and Southeast Asia prior to the former’s collision with Asia, he added.

“This might help explain the presence of genera that are not present in the Eastern Himalayas, but are found in South India, Sri Lanka and Southeast Asia,” he added. He gave examples of the skink genus Dasia and the pit vipers (genus Tropidolaemus).

David Blackburn from the Florida Museum of Natural History agrees. “Clearly, some lineages must have survived on India as it moved across the Indian Ocean during the late Mesozoic and early Cenozoic, but several studies, including this one, now support that colonisation of the Indian subcontinent by animals from Asia before India had fully collided with the Asian mainland,” he said.

With inputs from Sahana Ghosh.

This article was first published on Mongabay. Read the original here.

Jaw Fossil From English Beach Belongs to Monstrous Marine Reptile

The newly discovered bone was 25 percent larger than the same bone in the largest ichthyosaur skeleton found till date.

Washington: A jawbone fossil found on a rocky English beach belongs to one of the biggest marine animals on record, a type of seagoing reptile called an ichthyosaur that scientists estimated at up to 85 feet (26 meters) long – approaching the size of a blue whale.

Scientists said on Monday this ichthyosaur, which appears to be the largest marine reptile ever discovered, lived 205 million years ago at the end of the Triassic Period, dominating the oceans just as dinosaurs were becoming the undisputed masters on land. The bone, called a surangular, was part of its lower jaw.

The researchers estimated the animal’s length by comparing this surangular to the same bone in the largest ichthyosaur skeleton ever found, a species called Shonisaurus sikanniensis, from British Columbia that was 69 feet (21 meters) long. The newly discovered bone was 25% larger.

“This bone belonged to a giant,” said University of Manchester paleontologist Dean Lomax.

“The entire carcass was probably very similar to a whale fall, in which a dead whale drops to the bottom of the sea floor, where an entire ecosystem of animals feeds on the carcass for a very long time. After that, bones become separated, and we suspect that’s what happened to our isolated bone.”

Fossil collector Paul de la Salle, affiliated with the Etches Collection in Dorset, England, found the bone in 2016 at Lilstock on England’s Somerset coast along the Bristol Channel.

The jaw bone of a giant ichthyosaur found on an English beach is pictured in this undated handout photo. Credit: Dean Lomax, The University of Manchester/Handout via Reuters

“The structure was in the form of growth rings, like that of a tree, and I’d seen something similar before in the jaws of late Jurassic ichthyosaurs,” he said.

Ichthyosaurs swam the world’s oceans from 250 million years ago to 90 million years ago, preying on squid and fish. The biggest were larger than other huge marine reptiles of the dinosaur age like pliosaurs and mosasaurs. Only today’s filter-feeding baleen whales are larger. The blue whale, up to about 98 feet (30 meters) long, is the biggest animal alive today and the biggest marine animal ever.

The researchers estimated the new ichthyosaur at 66 to 85 feet long (20 to 26 meters).

It appears to have belonged to an ichthyosaur group called shastasaurids. Because the remains are so incomplete, it is unclear whether it represents a new ichthyosaur genus or is a member of a previously identified genus, said paleontologist Judy Massare of the State University of New York College at Brockport.

The research was published in the journal PLOS ONE.

(Reuters)

How Can We Stop the Feminisation of Sea Turtles in the Northern Great Barrier Reef?

Green sea turtles’ sensitivity to incubation temperatures is such that even a few degrees can dramatically change the sex ratio of hatchlings.

Green sea turtle. Credit: Flickr

In the northern part of Australia’s Great Barrier Reef, the future for green sea turtles appears to be turning female.

A recent study has revealed that climate change is rapidly leading to the feminisation of green turtles in one of the world’s largest populations. Only about 1% of these juvenile turtles are hatching male.

Among sea turtles, incubation temperatures above 29ºC produce more female offspring. When incubation temperatures approach 33ºC, 100% of the offspring are female. Cooler temperatures yield more males, up to 100% near a lower thermal limit of 23ºC. And if eggs incubate at temperatures outside the range of 23-33ºC the risk of embryo malformation and mortality becomes very high.

As current climate change models foresee increases in average global temperature of 2 to 3ºC by 2100, the future for these turtles is in danger. Worryingly, warmer temperatures will also lead to ocean expansion and sea-level rise, increasing the risk of flooding of nesting habitats.

How scientists are tackling the problem

Green sea turtles’ sensitivity to incubation temperatures is such that even a few degrees can dramatically change the sex ratio of hatchlings.

Sea turtles are particularly vulnerable because they have temperature-dependent sex determination, or TSD, meaning that the sex of the offspring depends on the incubation temperature of the eggs. This is the same mechanism that determines the sex of several other reptile species, such as the crocodilians, many lizards and freshwater turtles.

Scientists and conservationists are well aware of how future temperatures may threaten these species. For the past two decades they have been investigating the incubation conditions and resulting sex ratios at several sea turtle nesting beaches worldwide.

This is mostly done using temperature recording devices (roughly the size of an egg). These are placed inside nest chambers among the clutch of eggs, or buried in the sand at the same depth as the eggs. When a clutch hatches (after 50 to 60 days) the device is recovered and the temperatures recorded are analysed.

Research has revealed that most nesting beaches studied to date have sand temperatures that favour female hatchling production. But this female bias is not immediately a bad thing, because male sea turtles can mate with several females (polygyny). So having more females actually enhances the reproductive potential of a population (i.e. more females equals more eggs).

But given that climate change will likely soon increase this female bias, important questions arise. How much of a female bias is OK? Will there be enough males? What is the minimum proportion of males to keep a sustainable population?

These questions are being investigated. But, in the meantime, alarming reports of populations with more than 99% of hatchlings being female stress the urgency of science-based management strategies. These strategies must be designed to promote (or maintain) cooler incubation temperatures at key nesting beaches to prevent population decline or even extinction.

Sea turtle. Credit: Reuters

The challenge of reversing feminisation

There are two general approaches to the problem:

mitigate impacts at the most endangered nesting beaches
identify and protect sites that naturally produce higher proportions of males.

Several studies emphasise that the natural shading native vegetation provides is essential to maintain cooler incubation temperatures. Thus, a key conservation action is to protect beach vegetation, or reforest nesting beaches.

Coastal vegetation also protects the nesting beach against wave erosion during storms, which will worsen under climate change. This strategy further requires coastal development to allow for buffer zones. Construction setback regulations should be enforced or implemented.

When natural shading is not an option, clutches of eggs can be moved either to more suitable beaches, or to hatcheries with artificial shading. Researchers have tested the use of synthetic shade cloth and found it is effective in reducing sand and nest temperatures.

Other potential strategies involve adding light-coloured sand on top of nests. This can help by absorbing less solar radiation (heat) compared to darker sand. Beach sprinklers have also been tested to simulate the cooling effect of rainfall.

The effectiveness of these actions has yet to be fully tested, but there is concern about some potential negative side effects. For example, excess water from sprinklers may cause fungal infections on eggs.

Finally, as much as mitigation measures are important, these are always short-term solutions. In the long run, prevention is always the best strategy, i.e. protecting the nesting beaches that currently produce more males from deforestation, development and habitat degradation.

Our recent research on the largest green turtle population in Africa reports unusually high male hatchling production. We found almost balanced hatchling sex ratios (1 female to 1.2 males). We attributed this mostly to the cooling effect of the native forest.

This, and similar nesting beaches, should be designated as priority conservation sites, as they will be key to ensuring the future of sea turtles under projected global warming scenarios.

Sea turtles face an uncertain future

Sea turtles are resilient creatures. They have been around for over 200 million years, surviving the mass extinction that included the dinosaurs, and enduring dramatic climatic changes in the past.

There is potential for these creatures to adapt, as they did before. This could be through, for example, shifting the timing of nesting to cooler periods, changing their distribution to more suitable habitats, or evolution of critical incubation temperatures that produce males.

But the climate today is changing at an unprecedented rate. Along with the feminisation of these turtles in the northern Great Barrier Reef, sea turtles globally face many threats from humans. These include problems associated with by-catch, poaching, habitat degradation and coastal development, plus a history of intense human exploitation.

In 2018, the prevalence of these species depends now more than ever on the effectiveness of conservation measures.

Ana Rita Patricio, Postdoctoral research fellow, University of Exeter.

This article was originally published on The Conversation. Read the original article.

Remarkably Complete 150 Million Year Old Marine Reptile Fossil Found in Gujarat

This is the oldest and most complete fossil of an ichthyosaur to have been found in India, and it may shed new light on the evolution and range of these ancient reptiles.

An illustration of an ophthalmosaurus. Credit: Nobu Tamura/Wikimedia Commons, CC BY-SA 3.0

Lakshmi Supriya is a freelance science writer based in Bengaluru.

When dinosaurs roamed on land, and the archaeopteryx flew in the skies, a large, fish-like marine reptile, the ichthyosaur, swam in the waters off the coast of ancient India. We now know this because an almost complete fossil of the ancient animal was recently found in the Kutch (or Kachchh) region of Gujarat. This is the oldest and most complete fossil of an ichthyosaur to have been found in India, and it may shed new light on the evolution and range of these ancient reptiles.

“The find is very interesting because there is a bias,” Valentin Fischer, a palaeontologist at the University of Liege, Belgium, told The Wire. “Most of the data we have on diversity on Jurassic ichthyosaurs comes from a limited series of localities: western Europe and western Russia mainly, then North and South America. We really need the data from India and Africa to better understand the evolution of these animals.” Fischer was not part of the find.

There are only a handful of marine reptiles today. Saltwater crocodiles, sea turtles and sea snakes come to mind. These animals live and hunt in the water but need to surface to breathe. About 250 million years ago, there were plenty of them in Earth’s warm and humid oceans, and cruised the waters of the globe. It was in these conditions that the ichthyosaur first appeared in the form of an eel-like creature. Over the next 40 million years, it evolved to adapt itself perfectly to living in the ocean, with a streamlined body and flippers almost like those of a dolphin, swimming fast and deep.

The first notable ichthyosaur fossil discovery was made in the early 19th century, around the limestone cliffs of Dorset, UK, by Mary Anning. Since then, several fossils of the reptile have been found in Germany, Russia, Norway and North America. These modern nations were part of the northern landmass called Laurasia during the Jurassic period, about 200 million years ago. A few fossils have been found in South America as well, and younger fragments from Australia and Madagascar. These latter regions were then part of the southern continent, Gondwanaland, separated from Laurasia by an ocean called Tethys. India was then part of Gondwanaland; it would later separate and collide with the Eurasian landmass 40-50 million years ago.

The world in the late Jurassic period. The part known as India today is marked at no. 13. The route that the ichthyosaur could have taken from Laurasia to Gondwanaland is shown in pink. Source: PLOS

“The present find from the Kachchh is 152 million years old, which is later Jurassic in geological terms, and it is a nearly complete skeleton,” Guntupalli Prasad, a palaeontologist at the University of Delhi and lead author of the study describing their discovery, said to The Wire. The Kutch, a seasonally dry and arid area today, was at that time under the ocean. And although this area is known for its ancient fossils, vertebrate fossils are rare.

Geological and location map of the Upper Jurassic ichthyosaur site of Kutch, Gujarat. Caption and source: PLOS

In January 2016, researchers digging near Lodai village in Gujarat had been looking for invertebrate fossils when they found a bone that looked it belonged to a dinosaur; dinosaurs are vertebrates. This was unusual because the area was thought not to harbour fossils of vertebrate animals.

Field photograph (A) accompanied with a sketch (B) of the excavated ichthyosaur skeleton in the Katrol Formation near Lodai village. Caption and source: PLOS

So Prasad and his colleagues dug for about 10 days and gradually unearthed the ribs, forefin, tail, a part of the snout and finally the skull – all in that order, as if the ichthyosaur to which these bones belonged to had been trapped while diving down. In all, only a part of the skull, the end of the tail and the hind fins were missing. Although ichthyosaur fossils have been found before in India in the Kaveri basin, they were only in the form of isolated teeth and a few backbone fragments. The new find, on the other hand, is remarkable in terms of its completeness, even showing the curve of the backbone and the near-perfect placement of the forefins.

The team identified the fossil as an ichthyosaur’s because of certain distinguishing features, according to Prasad. The presence of fins instead of feet was key, and the arrangement of its fingers distinguished it from the other marine reptiles of its times. Another key feature was the presence of double-headed ribs – ribs that are attached to the backbone at two points. The total length of the assemblage skeleton was about 3.6 metres, which meant the adult ichthyosaur was large, about 5.5 metres long (when the missing parts were accounted for).

The new fossil has been identified as belonging to the family of opthalmosaurus, or “eye-lizard,” because of their extremely large eyes – the biggest of any known vertebrate. This enabled better vision that enabled these beasts dive deeper in ocean waters to hunt. In fact, this is one reason they thrived in the oceans. Another was their ability to give birth to live young ones instead of laying eggs as modern marine reptiles do. Scientists were able to attest to this feature using fossils discovered in China in 2014: they showed a mother ichthyosaur with an embryo inside her and one stuck in her pelvis.

Marine reptiles are known to have thrived between about 250 and 90 million years ago. But there are gaps in the knowledge of their ranges and how they evolved in different locations, mainly because fossil records have been concentrated in the northern hemisphere; there have been few findings in the south. “Indian localities provide access to the ichthyosaurs living in the southern margin of the Tethys ocean and, thus, of their shape, diversity, and palaeogeography. These findings provide the best specimens so far from this region and help detail the possible palaeogeographic routes these animals took during the Jurassic,” Fischer said.

Since the fossil from Kutch is closely related to fossils found in the UK, Prasad suggested that ichthyosaurs from the southern oceans, off the coasts of South America, western India and Madagascar, could have swum up north via the Tethys ocean. However, “this is a hypothesis, this needs to be tested,” he added.

Additionally, the well-preserved teeth of the ichthyosaur provide some clues about its diet. They show wear marks characteristic of eating hard food. According to Prasad, this suggests that the ichthyosaur was a top-tier predator in the oceans and fed on hard-shelled molluscs, such as the extinct ammonites and belemnites whose remains were found along with the ichthyosaur fossil. Or even small marine reptiles.

The real work has only begun. Prasad said that the next step is to prepare the skeleton for further study by removing the iron deposits on it and freeing it from its rock matrix. This will allow its species category to be identified with more precision. “The new fossil has demonstrated the potential of the Kutch Jurassic rocks for the discovery of marine reptiles,” he said.

He and his team also want to systematically explore the region further, studying the various geological formations in search of marine reptiles and other vertebrate fossils. He wondered if this was the only ichthyosaur that wandered near India – or if there could be many of its kind around the subcontinent. “That, of course, we have to explore further.”