FROGS
Frogs are generally found in the water while toads are generally found on land. Frogs are usually spend more time in water but are comfortable on land. They have clammy skin without scales and lay masses of eggs in a jelly-like mass. Both their skin and eggs are highly permeable. [Source: Virginia Morell, National Geographic, May 2001]
Frogs first emerged 190 million years ago. Today there are more than 3,500 species of frog and toads. Scientist discover about 50 new species a year. The live all over the wold, including the driest deserts, Arctic tundra, seawater mangrove swamps and up to 18,000 feet on the Tibetan plateau.
Frogs generally have sleek, slippery and smooth skin while toads are covered with rough warts. Frogs zip around with long jumps, while toads prefer to amble along with a slow walk, although when pressed they can execute short hops.
See Separate Article: AMPHIBIANS: CHARACTERISTICS, TYPES, THREATS factsanddetails.com
Toads
Toads are slow-moving creatures. They are generally not fast enough to escape predators. Instead they defend themselves with small organs called parotid glands that release poison and are found behind the ridges of their eyes or are arranged along the backs of the toad are two parallel rows. When stimulated these glands release a milky liquid which contain powerful poisons called bufotoxins. The poisons are powerful enough to paralyze a small dog, cat, weasel or fox. They can cause death if squirted into the mouth of a small animal. If you handle a toad wash your hands afterwards.
Toads feed on worms, spiders, pill bugs, centipedes, ground beetles, earthworms, and other crawling creatures, insects and small animals. Relaying an camouflage to hide their presence, they like to ambush their prey, lying still waiting for it pass and then zap its with a sudden movement from their sticky tongue — sort of like a chameleon — to lasso their prey. Potential predators that feed on toads include snakes, weasels, dogs and cats.
Toad mating and egg-laying take place in shallow ponds. The process usually takes place in the spring, beginning with long wrestling matches that can last for days between males trying to win the right to mate with the females. Sometimes the males try to mate with the females while simultaneously wrestling with several male rivals.
The fighting stops when the female finally lays her eggs which are fertilized outside her body by males who squirt their sperms over the eggs. As the eggs emerge, females secrete a jelly-like substance that surrounds and protects the eggs. The spawn is produced in the form of long, thin gelatinous ropes, which contain several thousand eggs. A few weeks later tadpoles appear and stay in the water for several months and eventually crawl out as baby toads.
Frog Characteristics
Frogs feed on mosquitos, aquatic insects, worms, crawfish, small fish and occasionally the chicks of small waterbirds. Frogs have long sticky tongues. They can open their mouth, snag an insect with their tongue and pull it into their mouths fast than the blink of an eye. The circles behind the eyes are the drumheads of the ears.
Laura Geggel wrote in Live Science: Frogs are famous for their fast tongues, and for good reason. More than 4,000 frog species can grab objects with their tongues faster than the human eye can blink, according to Alexis Noel, a research engineer at the Georgia Tech Research Institute who studies frog and cat tongues, previously reported on her website. She noted that frog mouths have a unique anatomy: "Unlike humans, frog tongues are connected at the front of the lower jaw, rather than at the back of the throat." In addition to its speed, the frog tongue is strong. The tongue of the horned frog can pull objects that are about 1.4 times the frog's body weight, a 2014 study in the journal Scientific Reports found. [Source Laura Geggel, Live Science, July 11, 2024]
Frogs are powerful swimmers and good jumpers. They are generally solitary, and usually most active at night, particularly on rainy nights. Some frogs hibernate by burrowing in the mud. The North American wood frog can survive off long as seven months in sub-freezing temperature, with the help of natural antifreeze in it body.
Tree frogs can climb tree trunks and building walls with their sticky toe pads. Some tree frogs can change their color to match their background. The can accomplish this with several layers of chromatophores, special color cells that can be opened or closed to adjust to skin color. Tree frogs lay their eggs in water like all amphibians.
Many frogs secrete compounds through their skin that have powerful antibiotic properties. Some frogs roll themselves into a ball and lie still to conserve water.
Frog Songs
The croaks, trills, peeps, grunts made by frogs are purely vocal and are produced the same way humans make sound do by pushing air back and forth through their vocal chords. Some frogs have vocal sacs on the other side of their throat that amplifies the sound.
Frogs are great singers. Only male frogs sing. They do so to attract females and inform males of their presence. Sometimes they call hundreds of time a night. Herpetologist Stan Rand told National Geographic, "It's the most energetically expensive thing a male frog ever does."
Before singing a frog sucks in a full load of air and then closes its nose and mouth. The air is pushed through into the vocal sac, which looks like an inflated balloon. Some species have one sac under the chin. Other species have two sacs, one on each side of the cheeks. Each species of frog has its own distinct song.
Predators sometimes use the songs to locate frogs. Frogs are fed on by a number predators, including snakes, herons, hawks, mammals and large fish. They escape by jumping, diving and swimming away. Many kinds of snake like to feed on frog eggs. When threatened by a snake the eggs one species Panamanian frog hatch prematurely.
Studies have shown that some species of frog response not only the calls and silences of their species for warnings of predators but also monitor the calls of other frog and animal species for clues on the presence of predators like bats, snakes and birds.
Breeding Frogs
Frogs gather together in the breeding season. Depending on the kind of frog, the females lay between 2,000 to 8,000 eggs. Mating usually takes place in ponds, pools or streams on rainy nights, with the male fertilizing the eggs while they float on the surface or they emerge from the female. Amplexus is the name of the embrace employed by the male on the back of the female while she is producing eggs. A pair of frogs can remain in this embrace for hours.
Among many species, the males protect the eggs. Some carry the froglets on their backs or even swallow the eggs and keep them in their vocal sacs until the froglets emerge from their mouth.
The development of a tadpole into a frog is called metamorphosis. Embryos develop into tadpoles in the jelly of the egg. After a few days when the tadpoles are strong enough they break out of the jelly and begins feeding on larvae. At this stage the tadpoles are not very developed. Over the following days they develops tails and external gills. Later they develop internal gills like a fish.
Depending on the species, the tadpole stage can last several weeks to a few years. During this time the tadpole is essentially a plant-eating fish. Then a remarkable metamorphosis takes place: it grows a set of lungs and then begins breathing oxygen from the air. The lungs grow larger and the gills become smaller and eventually disappear. Around this time legs appear and grow; the tail shrinks and disappears; and the mouth develops a hinged jaw. When the transformation is complete, an insect- and animal-eating frog is complete.
Frogs That Freeze Solid
Christine Peterson wrote in National Geographic: A college professor at my university years ago shocked his class with a demonstration. He showed off a wood frog that was still alive but frozen solid. Then suddenly, he threw it against a wall and it shattered. Everyone gasped. Moments later, he explained that he hadn’t actually thrown the frog. For dramatic effect he had switched the frog for a hunk of ice. But the goal was to illustrate a point: That a wood frog does in fact freeze as solid as ice to survive the winter. Then it thaws again in the spring. [Source: Christine Peterson, National Geographic, November 18, 2022]
The wood frog is one of the most frequently studied animals on Earth that freezes. When temperatures drop in the fall, it nestles in leaves and lets the cold creep into its body until it fully succumbs—heart, brain, and all. But it’s not the only species that essentially dies and then comes back to life. “The reason you freeze is to extend your range farther north or higher in elevation like the top of a mountain,” says Kenneth Storey, a professor of biochemistry at Carleton University in Ottawa, Canada, who studies freeze tolerance. “You can get a better niche in the world if you can freeze. So here’s the wood frog, it’s liquid, it’s hopping around, then ice comes on it from the outside,” says Storey. “Its skin gets frozen a little bit, and then ice penetrates into the frog through veins and arteries.”
From there it gets weirder. The frog’s eyes glaze over, its brain freezes, and ice pushes blood to the frog’s heart before eventually that, too, is rock solid. This transition requires major changes in biochemistry. The frog’s microRNA molecules reorganize cells to protect them from damage. Ice then slowly forms around the outside of organs and cells. At the same time, the frog’s liver pumps out incredible amounts of glucose—a syrupy liquid that acts like antifreeze for vital organs—that seeps everywhere including the insides of cells to keep them from shrinking and dying.
Then in the spring, Storey says, “the sun will shine, mud will form, they’ll warm up, and they’ll thaw.” The extent of their frozen-ness varies. Wood frogs in Alaska will freeze down to negative 5 degrees Fahrenheit. Others in North Carolina cool to 8.6 degrees. But the mechanisms are the same. And they’ve also been observed in other frogs, including the southern brown tree frog, the spring peeper frog, and cricket frogs, as well as in many insects and insect larvae.
Frog That Lives at 5,000 meters (16,400 Feet)
Nanorana parkeri (common names: High Himalaya frog, Xizang Plateau frog, Parker's slow frog, mountain slow frog) is a species of frogs in the family Dicroglossidae. It is found in Tibet (China) and in Nepal, but it is expected to be found also in Bhutan and parts of India. It is the second amphibian, and the first Neobatrachian, to have its whole genome published. [Source b17]
Nanorana parkeri are medium-sized frogs: males grow to a snout–vent length of about 44 millimeters (1.7 inche) and females to 48 millimeters (1.9 inches). Tadpoles are up to about 51 millimeters (2.0 inches in length.
This very common frog is found on high-altitude grasslands, forests, shrubs, lakes, ponds, marshes, streams and rivers in the Tibetan Plateau at elevations of 2,850–5,000 meters (9,350–16,400 ft) above sea level. It an explosive breeder in streams and marshes. There are no known major threats.
Frogs That Live in the Deserts of Australia
The desert spadefoot frog lives under the red sands of Simpson Desert sometimes for years before emerging after a rain. Water holings frog stays under ground for years and emerge when it rains and feeds and breeds. There at least 19 species of desert frog in Western Australia alone.
According to the Western Australia Museum: Desert frogs burrow underground during the dry months, in order to escape the searing sun. They can stay underground for many months while they wait for the next rains to fall. Whilst underground, many species produce a type of cocoon with many layers of their shed skin that covers their entire body (except for the nostrils). This helps to reduce water loss.
Most desert frogs only reproduce in response to a significant rainfall event. Females can then lay eggs in temporary pools. Some even lay their eggs in mud. These eggs then hatch when they are eventually flooded with water, and the tadpoles can swim straight into the water! Smart. One particular type of frog, the Northern Sandhill Frog, doesn’t even need water to hatch its eggs. These babies hop right over the tadpole stage, hatching out of their eggs as tiny, fully formed versions of their adult parents.
Scientists Regrow Amputated Frogs' Legs
In January 2023, in a study published in Science Advances, scientists at Tufts University and Harvard University's Wyss Institute showed how they had regrown amputated frog limbs using a chemical cocktail that induced growth of the limbs. “Currently, limb regrowth is limited to "salamanders and superheroes," the team said in a press release.
CBS News reported: Like humans, whose bodies cover major injuries with scar tissue, adult frogs are unable to naturally regenerate limbs.For the study, scientists began by applying a five-drug chemical cocktail infused in a silk protein gel to the African clawed frogs' stump and covered it in a silicone dome, that they call a BioDome, to seal it. They removed the dome after 24 hours — and then waited 18 months for the limb to regrow. [Source: Alexandra Larkin, CBS News, January 30, 2022]
“David Kaplan, Stern Family Professor of Engineering at Tufts and co-author of the study, said that "using the BioDome cap in the first 24 hours helps mimic an amniotic-like environment which, along with the right drugs, allows the rebuilding process to proceed without the interference of scar tissue." The five chemicals each had very specific functions, including inhibiting collagen production (which leads to scarring), reducing inflammation and sparking growth of nerves, blood vessels and muscles. The cocktail was meant to prevent the frog's immune system from closing off the stump. "It's exciting to see that the drugs we selected were helping to create an almost complete limb," said Nirosha Murugan, research affiliate at the Allen Discovery Center at Tufts and first author of the paper.
“The regrowth of an almost fully functional leg in many of the treated frogs was a hopeful result for the scientists. The new limbs had bones, nerves and several "toes" that grew from the ends of the limbs — although the toes did not have bones. The frogs could feel when the limb was brushed with a stiff fiber, and could use it to swim through the water.
Frogs and Fungus
Populations of frogs and amphibians have been devastated by the chytrid fungus, a disease of unknown origin that affects only some species and so far is beyond control. The microscopic fungus attaches to victims and thickens their skin, making it difficult for them to absorb water they need to survive. The disease is particularly widespread in Central and South America and Australia.
The spread of chytrid fungus is thought have occurred as a result of human activity. It probably introduced by African clawed frogs which were widely exported around the globe in the 1930s for medical research and pregnancy tests (frogs injected with the urine of pregnant women began laying eggs). It may have also been carried bullfrogs raised in South America for the United States frogs legs market. In Panama 48 amphibian species have come down with chytridiomycosis with their numbers plunging as much as 90 percent. In 2007 the chytridiomycosis fungus was found in pet frogs in Tokyo, the first cases of the disease in Asia.
The effects of fungus on frogs isn’t necessarily all bad. According to Live Science. In a 2016 study published in the journal Ecology and Evolution, researchers found that male common mist frogs (Litoria rheocola) infected with a fungus called Batrachochytrium dendrobatidis were more successful at finding a mate compared with uninfected frogs. Infected males called for a female mate more during the night than uninfected frogs, which may explain their reproductive success. A 2016 study in the journal Biology Letters found similar results while observing male Japanese tree frogs (Hyla japonica) infected with the same fungus. In that study, infected males called for a mate more rapidly and produced longer calls than uninfected frogs. [Source: Scott Dutfield, Katherine Gam Live Science, June 19, 2023]
Image Sources: Wikimedia Commons
Text Sources: Mostly National Geographic articles. Also David Attenborough books, Live Science, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
Last updated November 2024