Glass frog protects eggs, video


This 3 July 2017 National Geographic video says about itself:

The Glass Frog: Ultimate Ninja Dad | Animal 24

3 July 2017

A male glass frog is the lone protector of his eggs 24/7 until they hatch. Sometimes this means protecting them from their worst enemy.

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Dinosaurs extinct, frogs survived


This 2016 video is called Frogs: National Geographic Documentary HD.

From the University of California – Berkeley in the USA:

Dinosaurs’ loss was frogs’ gain: The upside of a mass extinction

88 percent of living frogs originated from an evolutionary radiation beginning at K-Pg boundary

July 3, 2017

Summary: Based on earlier studies, biologists believed that the vast majority of today’s frogs originated in a blossoming of new species 100 million years ago. New and more complete genetic data pinpoints this radiation much earlier: 66 million years ago at the Cretaceous-Paleogene boundary, precisely when much of life on Earth was wiped out by a comet or asteroid. Frogs took advantage of flourishing angiosperms to escape to the treetops into many more ecological niches.

Most of the frogs alive today owe a big thank you to the asteroid or comet that delivered the coup de grace to the dinosaurs.

A new study by Chinese and American biologists shows that if the calamity had not wiped the planet clean of most terrestrial life 66 million years ago, 88 percent of today’s frog species wouldn’t be here. Nearly nine out of 10 species of frog today have descended from just three lineages that survived the mass extinction.

The results, to be published this week in the journal Proceedings of the National Academy of Sciences, are a surprise, because previous studies of frog evolution pinpointed the blossoming of the main frog lineages today to about 35 million years earlier, in the middle of the Mesozoic era [rather: closer to the middle].

The new analysis of 95 genes from frogs within 44 of 55 living families shows that these three lineages started to take off precisely at the boundary between the Cretaceous and Paleogene periods — the K-Pg boundary, formerly called the KT boundary — when the last mass extinction occurred, and not 100 million years ago.

According to herpetologist and co-author David Wake, a University of California, Berkeley professor of the graduate school and a curator of the Museum of Vertebrate Zoology, new frog species likely radiated rapidly throughout the world because so many environmental niches were available after the animals occupying them disappeared.

“We think the world was quite impoverished as a result of the KT event, and when the vegetation came back, angiosperms dominated. That’s when trees evolved to their full flowering,” Wake said. “Frogs started becoming arboreal. It was the arboreality that led to the great radiation in South America in particular.”

Trees are an ideal habitat for frogs not only because they allow them to escape from terrestrial predators, but also because their fallen leaves provide protection while the frogs are on the ground, breeding habitat and plenty of food, such as insects. Trees and other flowering plants took off in the late Cretaceous, and were ready for exploitation by frogs after they recovered from the extinction.

Another adaptation that became popular was direct development, that is, producing young without a tadpole stage, which is standard for about half of all frog species today.

“The majority of the frogs that thrive now are thriving because of direct development of eggs in terrestrial situations,” he said. “It is a combination of direct development and use of arboreal habitat that accounts for a great deal of the radiation.”

Previous genetic analyses of frog evolution focused on mitochondrial DNA and how long the molecular clock had been ticking for mitochrondrial genes. However, analysis of molecular evolution in mitochondrial DNA often produces dates for lineage divergence that are too old. In the case of frogs, such analysis pinpointed the radiation of most living frogs at about 100 million years ago, which was a puzzle, since Earth’s environment was stable at that time. A changing environment typically drives evolution.

The new analysis, based on data assembled primarily by graduate student Yan-Jie Feng at Sun Yat-Sen University in Guangzhou, China, focused on the sequences of 95 genes located on chromosomes in the nucleus and how they changed over time. He and his colleagues gathered genetic data from 156 frog species and combined this with earlier information about two genes from 145 different frogs, for a total of 301 distinct frog species from all 55 families of frogs. The data were calibrated using 20 dates derived from fossils and Earth historical events.

The team, which includes scientists from the Florida Museum of Natural History at the University of Florida and the University of Texas, Austin, concluded that perhaps 10 groups of frogs survived the extinction, but only three of them (Hyloidea, Microhylidae, and Natatanura) flourished and diversified to claim habitats and niches around the world.

Nothing other than luck distinguishes the survivors, Wake said. Remnants of the other surviving lineages are scattered in isolated spots around the world, but are just as diverse today in their habitats and breeding strategies as the 88 percent.

Two of the three surviving lineages that subsequently radiated widely came out of Africa, which remained intact as the continents shifted around over the ensuing eons, with the breakup of Pangea and then Gondwana to form the continents we see today. The African rift zone and mountain building in West Africa generated new habitats for the evolving frogs, Wake noted. The third, Hyloidea, radiated throughout what became South America.

Today’s frogs, comprising more than 6,700 known species, as well as many other animal and plant species are under severe stress around the world because of habitat destruction, human population explosion and climate change, possibly heralding a new period of mass extinction. The new study provides one clear message for future generations.

“These frogs made it through on luck, perhaps because they were either underground or could stay underground for long periods of time,” Wake said. “This certainly draws renewed attention to the positive aspects of mass extinctions: They provide ecological opportunity for new things. Just wait for the next grand extinction and life will take off again. In which direction it will take off, you don’t know.”

Ranidae frog evolution: here.

Tree frog on video


This June 26 video is about a tree frog basking in the sun in Meijendel nature reserve in the Netherlands.

Fish to amphibian evolution, new research


This video says about itself:

The Evolution of Amphibians

23 January 2016

The first major groups of amphibians developed in the Devonian period, around 370 million years ago, from lobe-finned fish which were similar to the modern coelacanth and lungfish.

These ancient lobe-finned fish had evolved multi-jointed leg-like fins with digits that enabled them to crawl along the sea bottom. Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required.

Eventually, their bony fins would evolve into limbs and they would become the ancestors to all tetrapods, including modern amphibians, reptiles, birds, and mammals. Despite being able to crawl on land, many of these prehistoric tetrapodomorph fish still spent most of their time in the water. They had started to develop lungs, but still breathed predominantly with gills.

From the University of Calgary in Canada:

Fossil holds new insights into how fish evolved onto land

‘It’s like a snake on the outside, but a fish on the inside’

June 21, 2017

The fossil of an early snake-like animal — called Lethiscus stocki — has kept its evolutionary secrets for the last 340 million years.

Now, an international team of researchers, led by the University of Calgary, has revealed new insights into the ancient Scottish fossil that dramatically challenge our understanding of the early evolution of tetrapods, or four-limbed animals with backbones.

Their findings have just been published in the research journal Nature. “It forces a radical rethink of what evolution was capable of among the first tetrapods,” said project lead Jason Anderson, a paleontologist and Professor at the University of Calgary Faculty of Veterinary Medicine (UCVM).

Before this study, ancient tetrapods — the ancestors of humans and other modern-day vertebrates — were thought to have evolved very slowly from fish to animals with limbs.

“We used to think that the fin-to-limb transition was a slow evolution to becoming gradually less fish like,” he said. “But Lethiscus shows immediate, and dramatic, evolutionary experimentation. The lineage shrunk in size, and lost limbs almost immediately after they first evolved. It’s like a snake on the outside but a fish on the inside.”

Lethicus’ secrets revealed with 3D medical imaging

Using micro-computer tomography (CT) scanners and advanced computing software, Anderson and study lead author Jason Pardo, a doctoral student supervised by Anderson, got a close look at the internal anatomy of the fossilized Lethiscus. After reconstructing CT scans its entire skull was revealed, with extraordinary results.

“The anatomy didn’t fit with our expectations,” explains Pardo. “Many body structures didn’t make sense in the context of amphibian or reptile anatomy.” But the anatomy did make sense when it was compared to early fish.

“We could see the entirety of the skull. We could see where the brain was, the inner ear cavities. It was all extremely fish-like,” explains Pardo, outlining anatomy that’s common in fish but unknown in tetrapods except in the very first. The anatomy of the paddlefish, a modern fish with many primitive features, became a model for certain aspects of Lethiscus’ anatomy.

Changing position on the tetrapod ‘family tree’

When they included this new anatomical information into an analysis of its relationship to other animals, Lethiscus moved its position on the ‘family tree’, dropping into the earliest stages of the fin-to-limb transition. “It’s a very satisfying result, having them among other animals that lived at the same time,” says Anderson.

The results match better with the sequence of evolution implied by the geologic record. “Lethiscus also has broad impacts on evolutionary biology and people doing molecular clock reproductions of modern animals,” says Anderson. “They use fossils to calibrate the molecular clock. By removing Lethiscus from the immediate ancestry of modern tetrapods, it changes the calibration date used in those analyses.”

Dinosaur age caecilian amphibian ancestor discovered?


This video says about itself:

19 June 2017

A new analysis of a pair of tiny fossils found in the 1990s has helped scientists to uncover the backstory of the most mysterious amphibian alive. Researchers used 3D X-rays to map out the remains of a now-extinct species that walked the Earth [220] million years ago. They found that the species is a long-missing amphibious link that expands the known history of frogs, toads and salamanders by at least 15 million years. Chinlestegophis jenkinsi (artist’s impression) was a tiny subterranean carnivore.

From Science News:

New fossils shake up history of amphibians with no legs

Tiny skulls and other bits hint at unexpected backstory for today’s snake-shaped caecilians

by Susan Milius

3:30pm, June 19, 2017

Newly named fossils suggest that a weird and varied chapter in amphibian deep history isn’t totally over.

Small fossils about 220 million years old found along steep red slopes in Colorado represent a near-relative of modern animals called caecilians, says vertebrate paleontologist Adam Huttenlocker of the University of Southern California in Los Angeles.

Caecilians today have long wormy bodies with either shrunken legs or none at all. Yet the nearly 200 modern species of these toothy, burrow-dwelling tropical oddballs are genuine amphibians. The fossil creatures, newly named Chinlestegophis jenkinsi, still had legs but could be the oldest known near-relatives of caecilians, Huttenlocker and colleagues suggest.

A popular view of the amphibian family tree has put caecilians on their own long, peculiar branch beside the ancient frogs and salamanders. But a close look at the new fossils suggests a much earlier split from ancestral frogs and salamanders, the researchers propose June 19 in Proceedings of the National Academy of Sciences. The move puts the caecilians into “a strange but incredibly diverse” group, the stereospondyls, Huttenlocker says. These species included elongated, short-legged beasts with heads shaped like toilet lids.

Among the many stereospondyls, Huttenlocker speculates that caecilians came from “an aberrant branch of miniaturized forms that went subterranean.” And today’s legless burrowers could be this once-flourishing group’s sole survivors.

Promiscuous salamander reproduction research


This 2015 video is called Ambystoma andersoni, Anderson’s Salamander.

From the University of Iowa in the USA:

Promiscuous salamander found to use genes from three partners equally

Finding points to the inventive ways animals balance genetics and reproduction so their species will thrive

June 12, 2017

Summary: A study shows that a unique all-female lineage of salamander equally balances genes from the males of three other salamander species. The findings highlight the bizarre ways some animals reproduce in order to preserve their species.

A promiscuous salamander has found a simple genetic formula for success: Mate with multiple males and use equal parts of each partner’s genetic material in her offspring.

A University of Iowa-led team of biologists analyzed the genome of Ambystoma, a six-million-year-old salamander lineage that produces only female offspring. The team found most of its genetic profile is made up of equal contributions from males of three separate salamander species — Ambystoma laterale, Ambystoma texanum, and Ambystoma tigrinum.

The researchers think the all-female salamander’s balanced genome points to the bizarre ways some animals — from all-female populations of fish, lizards, and others — can use their genomes to maximize their chances of success.

“We’re hypothesizing the successful individuals have balanced gene expression,” says Maurine Neiman, associate professor in biology at the UI and an author on the paper, published in the journal Genome Biology and Evolution. “This balance might have been a prerequisite for the emergence and continued success of this particular hybrid lineage.”

Sexual reproduction is dominant in the animal world. The unisexual Ambystoma salamander engages in sex, but with a slightly different purpose. When it mates, the female acquires the male’s genes and then keeps only some, discarding others. This is known as kleptogenesis, or the theft of genetic material from male donors for reproductive purposes.

The UI researchers wondered how choosy the unisexual female is about which genes it keeps and uses when mating with males from different sexual salamander species. Using a specimen from the lab of Ohio State University biologist and study co-author H. Lisle Gibbs, the team analyzed nearly 3,000 genes in a unisexual female with three genomes (called a triploid). Of that total, they found 72 percent of the genes provided by the three male partners were expressed equally.

In other words, the all-female salamander chose to use roughly the same number of genes from each salamander species.

“It’s mostly balanced. The three genomes are mostly being expressed equally in this hybrid,” says Kyle McElroy, a graduate student in Neiman’s lab and the paper’s corresponding author. “What we’d like to find out is how the choosing and using occurs, and how these genes from different sexual salamander species come together to make a successful hybrid.”

It could be a case of keeping things simple. McElroy likens it to a sports team having a roster of equally competent players, with no star athlete whose injury would cripple its success.

“If you have a team that’s unbalanced and loses a top player, you won’t win,” says McElroy, a fourth-year graduate student from St. Louis. “But if every player is equal, then you don’t lose as much.”

So, rather than the female salamander individually selecting genes from the thousands available to her — a complicated process — the salamander appears to have found a balanced ratio of genes from the males of the other three species that works for her, and has settled on that.

“It would be difficult to maintain without balance,” McElroy says, “and that may be the key to this hybrid’s success.”