how many years have frogs existed

how many years have frogs existed

how many years have frogs existed

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how many years have frogs existed
how many years have frogs existed

Frog Fun Facts

Part of the Frogs: A Chorus of Colors exhibition.

General

  • There is evidence that frogs have roamed the Earth for more than 200 million years, at least as long as the dinosaurs.
  • The world‘s largest frog is the goliath frog of West Africa—it can grow to 15 inches and weigh up to 7 pounds. A goliath frog skeleton is featured in Frogs: A Chorus of Colors.
  • One of the smallest is the Cuban tree toad, which grows to half an inch long.
  • While the life spans of frogs in the wild are unknown, frogs in captivity have been known to live more than 20 years.
  • There are over 6,000 species of frogs worldwide. Scientists continue to search for new ones.
  • Toads are frogs. The word “toad” is usually used for frogs that have warty and dry skin, as well as shorter hind legs.

Frog Physiology

  • Frogs have excellent night vision and are very sensitive to movement. The bulging eyes of most frogs allow them to see in front, to the sides, and partially behind them. When a frog swallows food, it pulls its eyes down into the roof of its mouth, to help push the food down its throat.
  • Frogs were the first land animals with vocal cords. Male frogs have vocal sacs—pouches of skin that fill with air. These balloons resonate sounds like a megaphone, and some frog sounds can be heard from a mile away.

Locomotion

  • Launched by their long legs, many frogs can leap more than 20 times their body length.
  • The Costa Rican flying tree frog soars from branch to branch with the help of its feet. Webbing between the frog’s fingers and toes extends out, helping the frog glide.

Camouflage

  • To blend into the environment, the Budgett’s frog is muddy brown in color, while the Vietnamese mossy frog has spotty skin and bumps to make them look like little clumps of moss or lichen.
  • Many poisonous frogs, such as the golden poison frog and dyeing poison frog, are boldly colored to warn predators of their dangerous toxic skins. Some colorful frogs, such as the Fort Randolph robber frog, have developed the same coloring as a coexisting poisonous species. Although their skins are not toxic, these mimics may gain protection from predators by looking dangerous.

Surviving Extremes

  • Like all amphibians, frogs are cold-blooded, meaning their body temperatures change with the temperature of their surroundings. When temperatures drop, some frogs dig burrows underground or in the mud at the bottom of ponds. They hibernate in these burrows until spring, completely still and scarcely breathing.
  • The wood frog can live north of the Arctic Circle, surviving for weeks with 65 percent of its body frozen. This frog uses glucose in its blood as a kind of antifreeze that concentrates in its vital organs, protecting them from damage while the rest of the body freezes solid.
  • The Australian water-holding frog is a desert dweller that can wait up to seven years for rain. It burrows underground and surrounds itself in a transparent cocoon made of its own shed skin.
  • Frogs are freshwater creatures, although some frogs such as the Florida leopard frog are able to live in brackish or nearly completely salt waters.

Mating and Hatching

  • Almost all frogs fertilize the eggs outside of the female’s body. The male holds the female around the waist in a mating hug called amplexus. He fertilizes the eggs as the female lays them. Amplexus can last hours or days. One pair of Andean toads stayed in amplexus for four months.
  • The marsupial frog keeps her eggs in a pouch like a kangaroo. When the eggs hatch into tadpoles, she opens the pouch with her toes and spills them into the water.
  • Pipa pipa, the Suriname toad of South America (an enlarged model of a female with froglets is featured in the Museum’s Hall of Reptiles and Amphibians), carries her young embedded in the skin of her back. After mating, the eggs sink gradually into the female’s back, and a skin pad forms over the eggs. The developing juvenile frogs are visible inside their pockets for several days before hatching. They emerge over a period of days, thrusting their head and forelegs out first, then struggling free.
  • The gastric brooding frog of Australia swallows her fertilized eggs. The tadpoles remain in her stomach for up to eight weeks, finally hopping out of her mouth as little frogs. During the brooding period, gastric secretions cease—otherwise she would digest her own offspring.
  • Among Darwin frogs, it is the male who swallows and stores the developing tadpoles in his vocal sac until juvenile frogs emerge.
  • how many years have frogs existed
    how many years have frogs existed

How Frogs Benefited From The Dinosaurs’ Extinction

The timing of this rapid diversification came as a surprise, University of California, Berkeley herpetologist and report co-author David Wake tells The Two-Way. It’s about 35 million years later than previous research suggested.

As the Chinese and American researchers noted in a press release, the previous estimate was puzzling, “since Earth’s environment was stable at that time. A changing environment typically drives evolution.” They say that “analysis of molecular evolution in mitochondrial DNA [like in previous studies] often produces dates for lineage divergence that are too old.”

The new research focuses on nuclear genes instead, which Wake says can provide a “much clearer picture of what’s happening.”

Frogs are “master survivors,” Wake says, able to go underground and live through long periods of inactivity.

The scientists aren’t sure why three main lineages ultimately outperformed all the others that were living at at the time of the asteroid strike.

There continue to be remnants of other pre-asteroid lineages around the world, the scientists say, and they’re “just as diverse today in their habitats and breeding strategies” as those descended from the three dominant lineages.

frog species

Many of the new frog species also started to lay their eggs on land, skipping the tadpole phase and growing directly into a small frog. There are currently about 6,775 known frog species, and Wake says this trait is now found in about half of them.

What this research shows, Wake says, is that frogs have the proven ability to “[take] advantage of opportunities — in this case [an] ecological vacuum that existed following the mass extinction.”

Now, the scientists want to study what it was about these lineages that allowed them to perform so much better than the others that survived the extinction event.

Extinction event that wiped out dinosaurs cleared way for frogs

Unexpectedly, their analyses showed three major lineages of modern frogs — about 88 percent of living species — appeared simultaneously, evolving on the heels of the extinction event that marked the end of the Cretaceous Period and the beginning of the Paleogene 66 million years ago. Previous research suggested a more ancient origin of many of these modern frog groups.

“Frogs have been around for well over 200 million years, but this study shows it wasn’t until the extinction of the dinosaurs that we had this burst of frog diversity that resulted in the vast majority of frogs we see today,” said study co-author David Blackburn, associate curator of amphibians and reptiles at the Florida Museum of Natural History on the University of Florida campus. “This finding was totally unexpected.”

Herpetologist David Blackburn, shown with a Goliath frog from the museum’s collection, co-authored a study that presents a new frog tree of life.

FLORIDA MUSEUM OF NATURAL HISTORY PHOTO BY KRISTEN GRACE

The speed at which frogs diversified after the asteroid or comet impact that triggered a massive die-off of most plant and animal life suggests the survivors were probably filling up new niches on Earth, Blackburn said.

“We think there were massive alterations of ecosystems at that time, including widespread destruction of forests,” he said. “But frogs are pretty good at eking out a living in microhabitats, and as forests and tropical ecosystems rebounded, they quickly took advantage of those new ecological opportunities.”

Frogs rose to become one of the most diverse groups of vertebrates, with more than 6,700 described species. But sparse genetic data has hindered scientists from reliably tracing their evolutionary history and the links between frog families.

Blackburn joined researchers from Sun Yat-Sen University, the University of Texas at Austin and the University of California, Berkeley to tackle the mystery of frog evolution with a dataset seven times larger than that used in prior research. The team sampled a core set of 95 nuclear genes from 156 frog species, combining this with previously published genetic data on an additional 145 species to produce the strongest-supported evolutionary tree, or phylogeny, to date. The tree represents all 55 known families of frogs and generates a new timeline of frog evolution.

 

history

The researchers then used fossil records to translate genetic differences between frog lineages into dates at which they likely diverged from one another. When the analyses pointed to a simultaneous evolution of the three major frog clades — Hyloidea, Microhylidae and Natatanura — the researchers initially eyed the finding with skepticism, said Peng Zhang, a corresponding study author and professor in the department of biochemistry and molecular biology at Sun Yat-Sen University in China.

how many years have frogs existed
how many years have frogs existed
The analyses that generated this frog tree of life showed 88 percent of modern frogs evolved after the mass extinction that killed non-avian dinosaurs, marked here by a dotted red line.

GRAPHIC BY FENG ET AL. IN PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES

“Nobody had seen this result before,” he said. “We redid the analysis using different parameter settings, but the result remained the same. I realized the signal was very strong in our data. What I saw could not be a false thing.”

When examined in the context of the evolution of other animals, however, the finding makes sense, Blackburn said.

 

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“Looking at bird or mammal phylogenies, we can see a reflection of Earth’s history — its climatic and geologic events,” he said. “You’d expect these major events — mass extinction and the breakup of continents — would have impact on frog evolution and that divergences between major lineages would relate to those in some respect. We see that in this phylogeny.”

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