AMPHIBIANS
Amphibians such as frogs, toads and salamanders are cold-blood, egg-laying vertebrates. There are three orders: 1) Anura (frogs and toads); 2) Caudta (salamanders and newts); and 3) Gymnophiona (caecilians, legless wormlike creatures that live in leaf litter or streams).
As of late 2024, there were 8,806 known species of amphibians, comprised of: A) 7,757 species of Anura (Frogs and toads); B) 825 species of Caudata (Newts and salamanders); and C) 224 species of Gymnophiona (Caecilians). The number of known amphibian species continues to grow as new species are discovered each year. Since 1985, the total number of recognized species has increased by over 60 percent. [Source: Amphibia Web]
Amphibians are a food for larger animals and help keep insect populations and algae in check. The Americas are particularly rich in amphibian species but this is at least partly because detailed survey have not been done in places like West Africa, India, Sri Lanka and New Guinea. According to the IUCN Red List by the World Conservation Union list one in three amphibians species is threatened.
Websites and Resources: Amphibian Web amphibiaweb.org ; Amphibian Research Center frogs.org.au ; Frogland allaboutfrogs.org ; Frog Photos calphotos.berkeley.edu/browse_imgs/amphibian ; Amphibian and Frog Photos mongabay.com/topics/amphibians ; National Geographic National Geographic ; Save the Frogs savethefrogs.com ; Amphibian Survival Alliance amphibians.org ; Amphibian Ark amphibianark.org ; Froglife froglife.org ; Websites and Resources on Animals: Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; Encyclopedia of Life eol.org , a project to create an online reference source for every species; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org ; Biodiversity Heritage Library biodiversitylibrary.org
Amphibian Characteristics
Most amphibians need to keep their skin moist. They are in danger of dying if their skin dries out too much. All amphibians exude chemicals from their skin. After handling one you should wash your hands and refrain from putting your fingers in your mouth, eyes or ears.
Amphibians need to live near water and lay their eggs in water. Most amphibians lay soft shell-less eggs in water and abandon them. As is true with fish, the eggs are mostly fertilized outside the female’s body. The offspring are born with feathery gills used for breathing in water. Many amphibians burrow into the soil. Those with keel-shaped heads tend to scoop dirt side to side while those with round heads tend to ram straight ahead into the soil.
Most amphibians hide during day and come out at night and are often active in the early morning or at dusk and escape summer heat estivation and the severe coldness of the winter through hibernation. Their foods mainly consist of living creatures and in many cases they have no capacity to defend themselves against predators. Fish, snakes, birds and animals are all prey on them. Amphibians have a growth period of a few months and their ability in defending, diffusing and migrating is rather poor thus they are very dependent on environment they live in. [Source: Center of Chinese Academy of Sciences, kepu.net.cn]
History of Amphibians
First emerging about 350 million years ago, amphibians were the first backboned creatures to walk on land and they ruled the Earth for about 100 million years until they were eclipsed by reptiles. Amphibians are regarded as more primitive than reptiles because reptiles such as iguanas show physiological changes associated with pleasure — a rise in heart rate and body temperature — but amphibians don't.
The origin of amphibians is not completely understood as there are huge gaps in the fossil record. Frogs and salamanders are thought to have evolved from ancient amphibians known as temnospondyls while caecilians evolved from lepospondyls, another group of ancient amphibians. In 2009, a fossil of a 290-million-year-old “frogmander” was found that had traits of both frogs and salamanders. The discover of the creature, called Gerobatrachus, was announced by scientists from the University of Calgary in Nature in May 2008.
As of 2006 there were 5,700 know species of amphibians. Of these about a third are endangered. In 2009 researchers discovered 19,232 species new to science, most of these were plants and insects, but 148 were amphibians.
270-Million-Year-Old Amphibian That Looked Like Kermit
In March 2024, in a paper published in the Zoological Journal of the Linnean Society, paleontologists with the Smithsonian National Museum of Natural History announced the discovery of a 270 million-year-old amphibian that they named Kermitops gratus because it has wide eyes and a cartoonish grin like the Muppet’s Kermit the Frog. The skull of Kermitops is similar in size to the skull of another well-known Early Permian amphibian, Gerobatrachus, which had a head about an inch in length (2.5 centimeters). Today many frogs have bodies shorter than that length.
According to CNN: Predating the dinosaurs, Kermitops is believed to have roamed the lower Clear Fork Formation of Texas during the Early Permian Epoch 298.9 million to 272.3 million years ago. The skull of the ancient amphibianfeatures big oval eye sockets and — due to its slightly crushed state — a lopsided smile that researchers said reminded them of the Muppet icon. The fossil was first uncovered in 1984 by the late Nicholas Hotton IIII, a museum paleontologist who had excavated fossils from the Red Beds in Texas, an area known to be rich in Permian-age remains.[Source: Taylor Nicioli, CNN, March 22, 2024]
“One thing that Kermitops really shows is that the origins of modern amphibians are a little more complex than some of the research has led on,” said study coauthor Arjan Mann, a postdoctoral paleontologist at the Smithsonian National Museum of Natural History. Kermitops is not classified as a frog because the prehistoric amphibian does not share all the same traits and anatomy found in modern frogs, So said. But the researchers determined the specimen is from the group temnospondyls, which are believed to be the most common ancestor of all lissamphibians — a category that includes frogs, salamanders and caecilians, Mann added.
The researchers noted several features that the ancient amphibian shares with its modern-day relatives, including a similar location for the eardrum at the back of the skull, a small opening between the nostrils that produces a sticky mucus to help frogs catch their prey, and even evidence of bicuspid, pedicellate teeth that are unique to amphibians and are found in most modern amphibian species.
The presence of teeth and other modern features of this prehistoric species can help researchers to better understand the evolutionary transition amphibians went through to get their unique features, such as teeth, today. A June 2021 study found that some species of frogs have lost and again evolved teeth several times throughout their lineages.
But Kermitops had many features distinct from its modern relatives. The critter’s robust skull had additional bones and elements that have likely disappeared with evolution, and its elongated snout paired with a short region of the skull behind the eyes was unique to the species, most likely serving to aid in catching insects. The early fossil record for lissamphibians is considered to be fragmentary, according to a news release from the Smithsonian Institution, and is largely due to the creatures’ small size and delicate bone composition, which make the fossils difficult to preserve and find later,
Frogs and Toads
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: FROGS AND TOADS: CHARACTERISTICS, BEHAVIORS, ODDITIES factsanddetails.com
Salamanders
Salamanders are amphibians typically characterized by a lizard-like appearance and the presence of a tail in both larvae and adults. Newts and salamanders spend most of their daily lives on land. They are primarily nocturnal. In the day they like to hide in moist leaf litter or rotting logs. They mate and breed in water. All ten extant salamander families are grouped together under the order Urodela from the group Caudata. Salamanders never have more than four toes on their front legs and five on their rear legs, but some species have fewer digits and others lack hind limbs. Their permeable skin usually makes them reliant on habitats in or near water or other cool, damp places. Some salamander species are fully aquatic throughout their lives, some take to the water intermittently, and others are entirely terrestrial as adults. Salamanders are of particular interest to scientists because they are capable of regenerating lost limbs as well as other damaged parts of their bodies. [Source Wikipedia]
Heather Heying wrote in Animal Diversity Web (ADW): Approximately 55 extant species in 15 genera are recognized in this morphologically and behaviorally diverse family of salamanders. Geographic distribution is the largest of any salamander family, with four disjunct centers. Salamandrids occur primarily in Europe (throughout most of Europe, South into northern Africa and east into Asia), and Asia (especially India, Southern China, and mainland Southeast Asia). Two genera are endemic to North America. [Source: Heather Heying, Animal Diversity Web (ADW)]
The salamandrids are informally subdivided into two subgroups, the "true salamanders" (including the genera Chioglossa, Mertensiella, and Salamandra), and the newts (the remaining genera). The "true salamanders" tend to be smooth skinned, while the newts are unlike all other salamanders in having rough skin that is not slimy.
Most adult salamandrids are small, rarely exceeding 20 centimeters in length, and brightly colored. All salamandrids have toxic skin secretions (some produce tetrodotoxins), and many have bright warning coloration that is used in defensive displays. Newts are extremely poisonous at all stages of their life history. One character that appears to diagnose the family is the presence of a fronto-squamosal arch in most genera. Most species have well-developed lungs.
All salamandrids have courtship displays in which the male circles the female and rubs her, sometimes grasping her before depositing his spermatophore. Fertilization is internal, and no parental care has been reported. Salamandrid larvae are aquatic, except for a few viviparous species that give birth to fully metamorphosed young. Three life cycles found in salamandrids with aquatic larvae include metamorphosis into terrestrial adults (typical of "true salamanders"); metamorphosis into partially or wholly aquatic adults (typical of newts); and the triphasic life cycle of some Notophthalmus populations in which aquatic larvae move onto land as non-reproductive terrestrial efts, then return to the water after several years as aquatic adults. Facultative neoteny also occurs in some species of true salamanders. True salamanders live in burrows under logs or stones in moist woodlands and subalpine meadows, emerging only on mild, damp nights. Partially terrestrial adult newts returning to the water to breed often undergo a partial "reverse metamorphosis" back to the larval condition, growing fin-like extensions on their backs and tails. Some species show a strong tendency to return to the same aquatic breeding site year after year. Salamandrids eat small invertebrates and, in some cases, anuran tadpoles, which they detect with both vision and lateral line organs.
Interesting Species of Salamanders
The web-toed salamander, a 10-centimetre (3.9 inch) salamander, lives on steep hills in the Sierra Nevada mountains. When disturbed or startled it coils itself up into a ball, often causing it to roll downhill. Red-back salamanders are monogamous creatures that can be mean to their partners if they start engaging in throat notes with other salamanders, by withdrawing affection.
One of the most bizarre salamanders is the axoloyl, a 15-centimeter-long species found in Mexico that has beady eyes, a goofy smile and a head crowned with frilly gills that look like a strange alien headdress. Scientists like the creatures — also known as “water monsters” — because they reproduce easily in the lab, are able to regrow limbs, jaws, skin, organs and parts of its brain and spinal chord and have clear skin so you can see what is going on. In 2013 the ugliest animal competition included an axolotl, which has also been described as the animal that never grows up.
Some salamanders are able to grow back limbs that they have lost. Other animals can do this but what makes salamanders special is that they regrow many different body parts over and over throughout their life. After a salamander loses a body part, blood vessels contract quickly and limit bleeding. Skin cells then work fast to cover the wound and form what is called “blastena” — a collection of stemlike cells that will eventually become a new body part. In Mexico City, scientists are genetically modifying axoloyls that are able to regrow limbs, jaws, skin, organs and parts of its brain and spinal chord in hopes being able to do the same with humans someday.
Brazilian Tree Frogs — Amphibians That Pollinate Flowers?
Jennifer Nalewicki wrote in Live Science: While most frogs eat a diet rich in insects, one species in Brazil has its own method of nourishment: dunking itself headfirst into a flower's bulb to slurp up its sweet nectar. When the frog comes up for air, pollen grains stuck to its rust-colored body get dispersed as it hops from flower to flower in the forest. Scientists think this could be the first time an amphibian has been observed pollinating flowering plants, according to a study published in the June issue of the journal Food Webs. [Source: Jennifer Nalewicki, Live Science, May 6, 2023]
"We observed individuals entering large flowers and leaving covered in pollen without destroying the flower structures," lead author Carlos Henrique de-Oliveira-Nogueira, a graduate student at the Federal University of Mato Grosso do Sul in Brazil, told Live Science. "This was the first time this behavior (actively seeking fruits and flowers) was seen and documented."
It's long been known that species other than bees, including bats and birds, can act as pollinators. But scientists were surprised to see an Izecksohn's Brazilian tree frog (Xenohyla truncata) performing a similar behavior on a Brazilian milk fruit tree (Cordia taguahyensis), known for its creamy-white flowers, according to the study. One evening, the team watched as two frogs "lapp[ed] up nectar from inside the bell-shaped flowers" in eastern Brazil's Restinga forests and then spread the pollen around, The New York Times reported.
Normally, frogs prefer to dine on moths and insects, which they capture by sticking out their long tongues. "Most frog species are carnivorous in their adult phase," de-Oliveira-Nogueira told Live Science. He said there are other frogs that are known to feed on plant parts. But in Brazil, X. truncata is the only one. "Here, we confirmed how opportunistic X. truncata seems to be. It feeds on both insects and plants — apparently anything that is available for consumption," he told Live Science.
Felipe Amorim, a pollination ecologist at São Paulo State University in Brazil who wasn't involved in the study, told the New York Times: "We cannot say that these frogs are actually pollinators. They are flower visitors, they are flower-visitor frogs. We have a lot to learn about this novel interaction."
Threats to Amphibians
Amphibians are among the world's most endangered family groups: habitat loss, over-exploitation, invasive species, pollution, and disease has put nearly 41 percent of the world's amphibians are considered threatened with extinction.
Though they can be very adaptable they are often vulnerable to disruptions in their habitats. There are fewer amphibian species compared with other vertebrates. The distribution of amphibians can be quite widespread. Their habitats include plains, hills, high mountains and plateaus, everywhere except oceans and deserts. The highest elevation they have been found at is around 5000 meters.[Source: Center of Chinese Academy of Sciences, kepu.net.cn]
According to the official Red List by the World Conservation Union one in three amphibian species is threatened. About half are in decline. Nearly a quarter are endangered or extinct.
Decline of Amphibians
A total of 120 amphibian species disappeared between 1980 and 2006. One biologist called it “one of the largest extinction spasms of vertebrate in history.” Another said was the largest potential extinction since the dinosaurs.
In some places the populations of frogs, salamanders and other amphibians have crashed and in some cases become extinct. In other places amphibians have developed gross deformities such as extra legs or misplaced eyes. Possible causes of these problems include interspecies competition, climate change, ultraviolet radiation from a thinning ozone layer, pollution, overharvesting, disease and habitat destruction.
Pollution is blamed for some of the decline. Frogs have highly permeable skin and eggs that easily admit toxins. In some places introduced bullfrogs, trout and other fish species have driven out local species by gobbling up the local species and their eggs and outcompeting them for food. Studies have shown of the deformities seemed to be caused by tiny parasitic flat worms not chemical, pollution or global warming.
The situation is so dire that scientists launched a massive “Noah’s ark’ to capture frogs, toads and salamanders and put them in safe places. During the first stage of the project amphibians were collected and placed in houses and hotels rooms until new buildings to house could be built. The most intensive collecting is taking place in Mexico, Ecuador, Colombia and Panama.
Amphibians and Climate Change
In January 2006, Alan Ponds of the Monteverde Cloud Forest Preserve and Tropical Science Center in Costa Rica authored a study published in Nature that showed a link between frog deaths from chytridiomycosis fungus and global warming. The study focused on the disappearance of 70 species of harlequin frog in Central and South America. “Disease is the bullet killing frogs, but climate change is pulling the trigger,” Pounds said.
They seem to grow well under cool day time conditions and hot nighttime ones. In rainforests global warming might actually cause a cooling trend in the day as more clouds might be generated by a warming affect. More clouds could cause higher temperatures at night as the cloud keep warm air from escaping into space. The chytridiomycosis fungus grows better under these conditions.
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