Essays On Amphibians Definition

Amphibians are members of the classAmphibia. The living ones are frogs (including toads), salamanders (including newts) and caecilians. They are four-leggedvertebrates which are cold blooded.

Amphibians lay their eggs in water, usually in a foamnest. After hatching they are tadpoles, which live in the water and have gills. The tadpoles change into adults in a process called metamorphosis. When they are adult, they have lungs to breathe instead of gills, and legs. Adult amphibians also use their skin to take in oxygen, and some species of salamanders do not have lungs.

The earliest amphibians evolved in the Devonian from lobe-finnedfish which had jointed leg-like fins with digits. They could crawl along the sea bottom. Some 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 necessary.[1][2]

For tens of millions of years, during the Carboniferous and early Permian, amphibia were top predators on land, especially in the low-lying tropical river systems. In drier conditions, they were less effective, and the ancestors of mammals and reptiles (the Synapsids and Sauropsids) gradually took over the land. They laid cleidoic eggs, which had hard shells, and could be laid out of water. Most of the large, early, amphibians went extinct in the Triassic period; a few survived to the Lower Cretaceous.[2]

The only living amphibiana today are the Lissamphibia. These include the Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians). They are all rather small, compared with mammals or reptiles. The smallest frog and vertebrate in the world is the New Guinea frog (Paedophryne amauensis). The biggest amphibian is the Chinese Giant Salamander (Andrias davidianus).

Amphibia are found everywhere in the world, except Antarctica, and there are about 5,565 different species: 88% of them are in the Anura.[3] In number of species, they are more successful than mammals, though they occupy a smaller range of habitats. However, it is said that amphibian populations have been declining all over the world.[4] Conservation is therefore an important concern.

Living amphibia[change | change source]

Adaptations[change | change source]

Respiration[change | change source]

Amphibians like to live near freshwater in warm weather. There have also been species which live in forests, deserts and arctic conditions. Adult amphibians use lungs, and they also get oxygen through their skin, so long as it is moist.[5]

Defences[change | change source]

Amphibians may be camouflaged in brown and green, and if so they are prey for birds and reptiles. Their colour gives them camouflage, which is their main defence.

Alternatively, many other amphibia have toxic skin, which is harmful to predators. These are poisonous to eat. This is an important defence against predation. Connected to this is the use of warning colouration. They may be in vivid colours of red, black, and yellow. Research into the Rough-skinned newt and the Garter snake shows this is a typical case of co-evolution. Where they live in the same area, the newts get more poisonous, and the snakes develop more resistance to the poison.[6][7][8]

Sight[change | change source]

Amphibians have colour vision and depth of focus for clear sight. They also have eyelids, glands and ducts which keep the eyes moist. These are adaptations to life on land: amphibia were the first vertebrates to have these features.

Development[change | change source]

Some amphibians, such as the common coquí, lay eggs out of water (in this case, on palm leaves). The eggs develop directly into adult frogs, by-passing the tadpole stage. Others, like mudpuppies and olms, have a different development. In a process called neoteny, they become sexually developed as tadpoles, and continue to live in the water with gills.

Anura[change | change source]

Main article: Anura

The order Anura includes the frogs and toads. There is no fundamental difference between frogs and toads. Frogs have a short body, webbed digits (fingers or toes), protruding eyes, forked tongue and no tail. They are exceptional jumpers: many of their features, particularly their long, powerful legs, are adaptations to improve jumping performance. They often live in semi-aquatic or inhabit humid areas.[9]

A popular distinction is often made between frogs and toads on the basis of their appearance. Their warty skin is an adaptation for making their toxicslime. Apart from these glands, their skin is dry, and that is an adaptation to drier habitats. These features have evolved a number of times independently: convergent evolution. The distinction has no taxonomic basis. The only family exclusively given the common name "toad" is Bufonidae (the "true toads"), but many species from other families are commonly called "toads".[9]

Caudata[change | change source]

The order Caudata is the salamanders.

Newts are salamanders which spend their life in the water even though they are adults. They are classified in the subfamily Pleurodelinae of the family Salamandridae.

Respiration differs between species of salamanders. Species that lack lungs respire through gills. In most cases, these are external gills, visible as tufts on either side of the head. Some salamanders that are terrestrial have lungs that are used in respiration, although these are simple and sac-like, unlike the more complex organs found in mammals. Many species, such as the Olm, have both lungs and gills as adults.[10]

Some terrestrial species lack both lungs and gills and perform gas exchange through their skin. Even some species with lungs also respire through the skin in this manner.

The skin of salamanders secretes mucus. This helps to keep the animal moist when on dry land, keeps their salt balance while in water, and lubricates during swimming. Salamanders also secrete poison from glands in their skin, and some additionally have skin glands for secreting courtship pheromones.[10]

Axolotls, from the genus Ambystoma (or mole salamanders), are neotenic amphibians. This means they get to sexual maturity and reproduce while still in a larval form.

Defence mechanisms[change | change source]

Most salamanders and newts have some defence against predators, usually a poison which makes them uneatable. Their bright colours are warning colouration. If, instead, they are camouflaged, this means they are probably not protected by a toxin.

The second line of defence is to shed their tail, which can grow again. The tail wriggles a bit, attracts the predator while the business part of the salamander moves off.

Other characteristics[change | change source]

There are over 350 lungless salamanders. Most of them are terrestrial and are active in daytime. Lungless salamanders may communicate with their nose.[11]p168Slender salamanders are found in the Pacific Coast. They are sometimes called "worm salamanders". This is because they have slimmer (skinny) bodies than most salamanders.[11]p182 If touched, slender salamanders will bounce on the ground and then run away.

Gymnophiona[change | change source]

The order Gymnophiona includes the caecilians. These are long, cylindrical, limbless animals that look like snakes or worms. Their skin has circular folds, increasing their similarity to the segments of earthworms. Some are aquatic but most live underground in burrows they hollow out. Many caecilians give birth to live young, and in the animals that do not do this, the eggs may undergo metamorphosis before they hatch. Caecilians are found in tropical Africa, Asia and Central and South America. There are 171 different species.

They are burrowing amphibians. This means that they dig themselves in wet soil like worms. Their heads are strong and have bones that help them dig.[12]p7 Because caecilians have a lot of vertebrae, they can bend easily.

Reproduction[change | change source]

Amphibians are the only vertebrates to go through metamorphosis. This means that their young look different from their adult.[13]p8 Amphibians usually reproduce in early spring to late summer, though some reproduce in winter and fall.[11]p156 Most frogs and toads, such as the common frog (Rana temporalis), gather in large groups to ponds, rivers, swamps and lakes to breed.[13]p10 Male frogs and toads may croak to attract a female. When a female frog has chosen a mate, the male frog hops on top of her. They swim together as she lay eggs in the water.[12]p7 Sometimes, males fight to mate with a female.[12]p7 Frogs can lay up to 100 to 60,000 eggs in one clutch. This is called "frogspawn".

It is a fundamental feature of amphibia that their reproduction is, one way or another, tied to water. This is because their eggs, although covered by jelly, cannot survive long in dry conditions.

Eggs[change | change source]

Most female amphibians lays her eggs in water. Males release sperm to fertilize them. The eggs are laid one by one or in batches. Batches of eggs can look like a long chain or a ball of foam. They may wrap their eggs around plants in the water. They do this so their eggs will not drift away.[13]p8

Tree frogs usually lay their eggs on a leaf in a rainwater pool. Bullfrogs, such as the male American bullfrog and the male African bullfrog, stay with their tadpoles and protect them from predators. They also move their tadpoles by using their nose to dig a channel to another place where there is more water.[13]p9 They do this so their tadpoles do not dry up. Most amphibians leave their eggs to look after themselves. Fish and other animals eat most of their eggs. Male midwife toads carry their eggs on their backs. When they are ready to hatch, the toad goes back to the water and release them.[12]p10

Tadpoles[change | change source]

Tadpoles do not have lungs when they hatch and instead have gills. Because gills have a large surface area, tadpoles can get more oxygen by using them. Young tadpoles have their gills exposed. When they get older, their gills are covered over by skin.[13]p6 When they hatch, tadpoles eat constantly. The tadpoles eat what is left of their eggs, this is usually their first food.[13]p8

Frog, toad and newt tadpoles eat plants such as algae and pondweed or filter feed. When they get older, they may start to feed on tiny animals in the water. Salamander tadpoles and surinam horned toad tadpoles are carnivorous throughout their tadpole stage.[13]p9 Surinam horned toad tadpoles are very aggressive. They eat other tadpoles if food is nowhere to be found. The eggs of the spadefoot toad hatches in three days. Their tadpoles complete their metamorphosis in six to eight days. This is because spadefoot toads lay their eggs in places where water will dry up soon.[13]p13

Tadpoles of frogs and toads start to grow their back legs first. They then grow front legs a few weeks later. When tadpoles grow their limbs they are called "froglets". This is because they look rather like a smaller version of adult frogs and toads. Tadpoles will also start to grow a backbone after growing their front limbs. After this, their mouths get bigger and their eyes will stick out more. After a tadpole has grown its hands, their tails continue to get shorter until there is nothing left of them.[13]p11

Habitats[change | change source]

Salamanders and newts can be found living in streams. Salamanders can be found in rotten logs, holes or underground places that are wet such as under leaves.[11]p152 Web-toed salamanders live in habitats where there are a lot of rocks. They like to hide under rocks and stones.[11]p195 The tailed frogs, like to live in cold water habitats.[11]p199 In their habitat, amphibians like to live where there are a lot of places to hide. These include nearby small trees, logs and plants. While underwater they like to hide near aquatic plants and rocks. Tree and dart frogs like to live in forests on trees, plants and on the ground under leaves.

Some amphibia can be found living in the desert or the arctic.[13]p12 The desert froglet lives in the desert. They are only active at night, when temperatures are much cooler. It rarely rains in the desert and because of this, desert frogs will burrow to keep cool. They use their mucus to keep them wet. They will spread it all over their bodies. The mucus will harden to keep the water it produces from escaping. Once the desert frog has done this, it will stay in its cocoon and will not move. They will stay like this for several months to years until a rainstorm. Desert frogs and toads lose water more quickly. The spadefoot toad will spit on the ground. Once they have done this, they will lay on it. Their bodies will take in the water. Their bodies are thin and have a lot of blood vessels, this helps them to be able to take water through their skin. The California newt can survive a fire by spreading its mucous over its body.[13]p12

Arctic frogs such as the wood frog, moor frog and the common frog has to live with freezing temperatures for a long time. They will burrow in places where they can get into a cocoon. Like every living organisms, amphibians must have water to survive. Amphibians however, need freshwater. Some frogs such as burrowing frogs can keep water in their bladders. This allows them to stay underground without drying up. The crab-eating frog lives near water that is somewhat salty. They will eat saltwater crabs. Torrent salamanders lives in cold waters. Because of this they have shorter lungs. Short lungs helps them to float easily.

Distribution[change | change source]

Amphibia are world-wide, though restricted in distribution by their need for moist or watery habitats to reproduce.

Anatomy[change | change source]

Skin[change | change source]

Many amphibia have secretions in their skin which makes them toxic. They do not produce toxins themselves.[14] They get toxins from what they eat. They eat insects in their habitat. These insects get the poison from a plant. The toxin has been discovered in beetles.[14] This means that they are likely the cause of poisons found in amphibians. Amphibians do not produce batrachotoxin in captivity, which means that it is not harmful to touch them. The American Indian tribe comechingóns used the toxins of the arrow dart frogs when hunting.[14]

Newts in the genus Taricha has a poison called tetrodotoxin, a neurotoxin. Scientists believe that toxins in newts are caused by bacteria in the genera Pseudoalteromonas, Pseudomonas and Vibrio. Because of this, the newts do not have a lot of predators. However, some species of snakes have develop a resistance. This means that they can eat newts without the toxin hurting them. It is a case of co-evolution.

Senses and skeletal system[change | change source]

Amphibians' eyes have lids, glands and ducts. They have good colour vision[15] Caecilian eyes are small and dark. Most of them are blind. Most amphibians have a good sense of smell, even underwater.

The skeletal system of amphibians are similar to other four-legged animals. They have a spine, rib cage, long bones such as the humerus and femur. They also have short bones such as the phalanges, metacarpals, and metatarsals. Most amphibians have four limbs, except for caecilians. The bones in amphibians are hollow and do not weigh much.[16]

Diet[change | change source]

Amphibians are predatory animals. They mostly eat live invertebrates and animals that do not move too quickly. These include caterpillars, earthworms, crayfish, water beetles, snails and dragon fly larvae.[17]p667 Many amphibians use their sticky tongues to catch their prey. They will swallow the animal whole, but may chew it just a bit for it to go down their throats. The Ranidae family and the Ceratophrys genus will eat almost anything they can fit into their mouths.[17]p668 These include rodents, birds, ducklings, small fish and small mammals.[18] Most frogs are cannibalistic, and will eat each other if food is no where to be found. Some amphibians will even eat their own tadpoles and eggs if there is no food for them.[19]

Feeding in captivity[change | change source]

In captivity, pet frogs will be given crickets, worms, small fish, rodents and fruit flies.[20] Adult amphibians can help decrease the mosquitopopulation by eating most of their larvae.[21]

Caecilians eat earthworms, termites and beetle larvae, and also small lizards.[22]p31 Caecilians rely on their smell to find food. They like to eat earthworms and will find them by picking up their chemical signals. Salamanders and newts are fed a lot of different types of worms. These include blood worms and earthworms. They can eat small fish such as goldfish, fathead minnows and guppies. Salamanders also eat crickets and pinkies, which are baby rats.[17]p771

Conservation[change | change source]

The amphibian population have been decreasing from all locations in the world.[4] Scientists have said that the declining of amphibians is one of the most critical threats to global biodiversity.[4] A number of causes are believed to be involved. These include habitat destruction, over-exploitation, pollution, introduced species, climate change, destruction of the ozone layer, and diseases like chytridiomycosis. Ultraviolet radiation damages the skin, eyes and eggs of amphibians. However, the declines of amphibian population are still not understood.[23]

The Amphibian Conservation Action Plan (ACAP) have released a global strategy to help the amphibian population. It was developed by over 80 leading experts.[24] The Amphibian Specialist Group of the World Conservation Union (IUCN) are working on another global strategy to help amphibian populations.[24] The Amphibian Ark (AA) is an organization that was created to help the public be aware of the decline in amphibian populations. They have been working with zoos and aquaria around the world. They try to encourage them to create a natural habitat for threatened amphibians.[24] Another project is the Panama Amphibian Rescue and Conservation Project (PARCP) which are trying to spread awareness about chyridiomycosis. The disease is spreading into eastern Panama and threatening all amphibians living there.[25]

On January 21, 2008, Evolutionarily Distinct and Globally Endangered (EDGE) released a statement to the public.[26] It was created by Helen Meredith, who identified nature's most endangered species. Meredith explains that 85% of the top 100 endangered amphibians list are receiving little to no conservation attention.

Human use[change | change source]

As food[change | change source]

Bullfrog legs are a source of food for Southern United States and the Midwestern United States.[27] People hunt bullfrogs at night near rivers. The bullfrogs' legs are cooked, while their backs are fried.[28]p9 In China, bullfrogs are sold alive for eating. However, they are later cooked dead with vegetables. In the state of California, people must have a license to catch bullfrogs for food.[29]p256 In schools, bullfrogs are dissected in biology classes. Usually, this is done in grammar school.[30]p85 The dissecting is a method for teaching students the anatomy of a bullfrog.[30]p85 The emperor newt is hunted in China for food. They are also used there for medicine. Burrowing frogs are able to hold water in their bladder, because of this indigenous Australians use them to drink water.[13]p13

As pets[change | change source]

Amphibians are also kept as pets.[31]p4 They are kept in aquariums or a terrarium. A terrarium is a tank that is decorated with plants and soil on one side. On the other side, there is water. Most amphibians would need one place for land and another for water.[31]p8 Each type of amphibian should have its special needs taken care of. Semi-aquatic amphibians need both land and water divided in the tank. Tropical frogs would need mist and high humidity in their terrariums.[32]p7 Water for amphibia needs dechlorination. The chlorine in tap water can kill amphibia. Some amphibians popular exotic pets, and are found in pet stores that sell reptiles.[31]p22

Related pages[change | change source]

References[change | change source]

  1. ↑Clack, Jennifer A. 2002. Gaining ground: the origin and evolution of tetrapods. Indiana University Press, Bloomington IN. ISBN 0-253-34054-3
  2. 2.02.1Carroll, Robert 2009. The rise of amphibians: 365 million years of evolution. Baltimore: The Johns Hopkins University Press. ISBN 978-0-8018-9140-3
  3. Pough F.H.; et al. (2003). Herpetology. 3rd ed, Benjamin Cummings. ISBN 0131008498. 
  4., M.L. (2007). "Amphibian decline or extinction? Current declines dwarf background extinction rate". Journal of Herpetology41 (3): 483–491. doi:10.1670/0022-1511(2007)41[483:ADOECD]2.0.CO;2. 
  5. ↑Duellman, William E. & Linda Trueb 1994. Biology of amphibians. Johns Hopkins University Press. ISBN 978-0-8018-4780-6
  6. ↑Science Daily
  7. ↑Garter snake info
  8. ↑Geffeney, Shana L. et al. 2005. Evolutionary diversification of TTX-resistant sodium channels in a predator-prey interaction. Nature434: 759–763.
  9. 9.09.1Zweifel, Richard G; Cogger H.G. & Zweifel R.G. 1998. Encyclopedia of reptiles and amphibians. San Diego: Academic Press. pp. 91–92. ISBN 0-12-178560-2
  10. 10.010.1Cogger, Harold G. ed 1998. Encyclopedia of reptiles and amphibians. San Diego: Academic Press. ISBN 0-12-178560-2.
  11., Robert Cyril 2003. A field guide to western reptiles and amphibians. Houghton Mifflin Harcourt. ISBN 0395982723
  12., Angela 2004. Living nature: amphibians. Black Rabbit. ISBN 1932333339
  13. 13.0013.0113.0213.0313.0413.0513.0613.0713.0813.0913.1013.11Morgan, Sally 2004. Amphibians. Heinemann-Raintree. ISBN 1410910466
  14. J.P. et al (November 2004). "Melyrid beetles (Choresine): a putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds". Proc. Natl. Acad. Sci. U.S.A.101 (45): 15857–60. doi:10.1073/pnas.0407197101. PMC 528779. PMID 15520388. 
  15. Duellman, William E.; Zug, George R. (2012). "Amphibian". Encyclopædia Britannica Online. Encyclopædia Britannica. Retrieved 2012-03-27. 
  16. Maglia A.M.; et al. (2007). "AmphibAnat". The amphibian anatomical ontology web project. Retrieved 2012-03-25. 
  17., Kentwood David 2007. The ecology & behavior of amphibians. University of Chicago Press, ISBN 0226893340
  18. "American Bullfrog". Retrieved 11 July 2012. 
  19. ↑Lannoo, Michael 2005. Amphibian declines: the conservation status Of United States species. University of California Press, 543. ISBN 978-0-520-23592-2
  20. ↑Starosta, Paul & Moncuit, Teddy 2006. Frogs and other amphibians. ACC Distribution, 122. ISBN 978-1-905377-05-3
  21. ↑Purser, Phillip 2006. Tadpole care. TFH Publications, 34. ISBN 978-0-7938-1035-2
  22. ↑Campbell, Jonathan A. 1999. Amphibians and reptiles of Northern Guatemala, the Yucatán, and Belize. University of Oklahoma Press, ISBN 0806130660
  23. "Amphibian Specialist Group". Retrieved 2012-03-30. 
  24."Amphibian Conservation Action Plan". IUCN. Retrieved 2012-03-30. 
  25. "Panama Amphibian Rescue and Conservation Project". Retrieved 2012-03-30. 
  26. "Evolutionarily distinct and globally endangered". Retrieved 2012-03-30. 
  27. The illustrated encyclopedia of North American reptiles and amphibians: an essential guide to reptiles and amphibians of USA, Canada, and Mexico, MobileReference, 2008, ISBN 978-1-60501-459-3 
  28. ↑Gray, Susan 2009. Bullfrog (animal invaders). Cherry Lake Publications. ISBN 978-1-60279-327-9
  29. ↑Storer, Malcolm 2004. Experimental approaches to conservation biology. University of California Press. ISBN 978-0-520-24024-7
  30. 30.030.1Glotzhaber, Robert 1973. The life cycle of a Bullfrog. Children Press. ISBN 978-0-87191-233-6
  31., Steve 2007. Frogs and toads: your happy healthy pet. Wiley ISBN 0470165103
  32. ↑Nelson, Robin 2002. Pet frog. Lerner. ISBN 0822512718

Reference books[change | change source]

  • Morgan, Sally (2004), Amphibians, Heinemann-Raintree Library, ISBN 1410910466 
  • Richardson, Adele (2006), Amphibians, Capstone Press, ISBN 0736849416 
  • Carroll, Robert L. (2009), The rise of amphibians: 365 million years of evolution, The Johns Hopkins University Press, ISBN 978-0-8018-9140-3 
  • Stefoff, Rebecca (2007), The Amphibian class, Marshall Cavendish, ISBN
Eryops, typical of the large-size early amphibians 310–295 million years ago
Frogs such as this edible frog has smooth (soft) wet skin
This fire salamander has yellow and black stripes along its body: typical warning colouration.
Chinese fire-bellied newts has red stripes on their front body, which they can raise when attacked. This is also warning colouration.
Frogs eggs are called "frogspawn"
Some amphibians lay eggs that are very clear. This makes it easy to watch a tadpole grow inside its egg.
This orange-thighed Frog tadpole has only a head and a tail. It will grow back legs and front hands in a couple of weeks. It will then loose its tail and become a young frog.
Most frogs like to spend their time in the water hiding near aquatic plants.
This poison dart frog's skin is blue. This color warns animals that they are toxic.
Most amphibians have a good sense of smell. Their eyes have color and clear vision.
Amphibians are predatory animals. If there is no food to be found, they will eat each other.
Bullfrogs being sold alive at a supermarket in China.
General Conference
See also Amphibians - Advanced
Skill Level 1
Year of Introduction: 1945

1. What are the characteristics of amphibians?[edit]

Amphibians live half of their lives in water and half on land. They are cold-blooded vertebrates. Amphibians are able to breathe through their skin, making them very sensitive to anything they come in contact with, including human hands. When observing amphibians, one should never touch them. Amphibians have toes rather than claws.

2. Name the two main orders of amphibia and tell how to distinguish between them.[edit]

Order Anura (frogs and toads)
Adult frogs and toads are characterized by long hind legs, a short body, webbed digits, protruding eyes and the absence of a tail. Most have a semi-aquatic lifestyle, but move easily on land by jumping or climbing. They typically lay their eggs in puddles, ponds or lakes; and their larvae, called tadpoles, have gills and develop in water.
Order Caudata (newts and salamanders)
Cuadata have slender bodies, short legs, and long tails. The moist skin of the amphibians fits them to habitats either near water or under some protection on moist ground, usually in a forest. Some species are aquatic throughout life, some take to the water intermittently, and some are entirely terrestrial as adults. Salamanders superficially resemble lizards, but are easily distinguished by their lack of scales. They are capable of regenerating lost limbs.

3. Distinguish between toads and frogs.[edit]

The use of the common names "frog" and "toad" has no taxonomic justification. From a taxonomic perspective, all members of the order Anura are frogs, but only members of the family Bufonidae are considered "true toads". The use of the term "frog" in common names usually refers to species that are aquatic or semi-aquatic with smooth or moist skins, and the term "toad" generally refers to species that tend to be terrestrial with dry, warty skin. An exception is the Fire-bellied toad (Bombina bombina): while its skin is slightly warty, it prefers a watery habitat.

4. How do amphibians protect themselves?[edit]

The first line of defense for amphibians is to not be seen by a potential predator. The small size and coloration of many species help in this regard, but sometimes, rather than blending in, frogs are very brightly colored. The coloration in this case serves as a warning, for these frogs are poisonous.

Many frogs contain mild toxins that make them distasteful to potential predators. For example, all toads have large poison glands—the parotid glands—located behind the eyes on the top of the head. Some frogs, such as some poison dart frogs, are especially toxic.

Salamanders have the ability to detach their tails at will. When a predator captures a salamander by the tail, the salamander detaches its tail and escapes. The tail regenerates or grows back.

5. Make a list of amphibians that should be found in your locality. Identify five and tell where you found them. OR Collect pictures or sketch five different amphibians which you can identify and tell where they are found.[edit]

To do:
Expand this section to include more species, such as giant salamander and newts.

Gymnophiona (Caecilians)

Where found: Caecilians are found in wet tropical regions of Southeast Asia, India and Sri Lanka, parts of East and West Africa, the Seychelles islands in the Indian Ocean and in northern and eastern South America.

Description: Caecilians completely lack limbs, making the smaller species resemble worms, while the larger species with lengths up to 1.5 meters resemble snakes. The tail is short or absent. They have a strong skull, with a pointed snout used to force their way through soil or mud.[2] In most species, the number of bones in the skull are reduced and fused together, and the mouth is recessed under the head. Owing to their underground life, the eyes are small and covered by skin for protection, which has led to the misconception that they are blind. This is not strictly true, although their sight is limited to simple dark-light perception. All caecilians possess a pair of tentacles, located between their eyes and nostrils. These are probably used for a second olfactory capability, in addition to the normal sense of smell based in the nose.

Lithobates (Rana) catesbeianus (Bullfrog)

Where found: The American Bull Frog is native to North America. They are found in the United States, Canada and Mexico, east of the Rocky Mountains, but have been introduced to many other localities throughout the world. In Europe and the western U.S., measures are often taken to control its spread because it competes with, and often drives out, native species.

Description: The bull frog is a large species that has many similarities to its 'sister species' of toad, and can grow to a length of 6 inches (15 cm) with a weight of up to 1.5 lb (750 g). Females are typically larger than males. They are generally varying shades of green or brown, with dark brown, dark green, or black blotching and a yellow or white underside. Bull frogs are carnivorous and will consume almost anything that fits into their mouth which they can overpower, including insects, small mammals, fish, snakes, and even other frogs. They tend to eat more dragonflies than flies. The adult frog can live up to 13 years.

Anaxyrus (Bufo) americanus (American Toad)

Where found: The American toad is a common species of toad found throughout the eastern United States and Canada.

Description: The American toad is a medium sized toad usually found in the range from 2 to over 3 1/2 inches. The color and pattern is somewhat variable. The Eastern American toad has spots that contain only one to two warts. It also has enlarged warts on the tibia or lower leg below the knee. While the belly is usually spotted, it is generally more so on the forward half (in some rare individuals there may be few or no spots).

Hyla versicolor (Grey Tree Frog)

Where found: Grey tree frogs inhabit a wide range, and can be found in most of the eastern half of the United States, as far west as central Texas. They also range into Canada in the provinces of Ontario and Manitoba, with an isolated population in New Brunswick.

Description: Grey tree frogs live primarily in trees, spending time in wooded areas, usually not far from a permanent water source. On rainy evenings they can often be found calling in or near shallow, temporary pools of water. They are nocturnal and insectivorous, consuming most any small arthropod they can catch. Mating occurs throughout the spring and summer months.

Hyla crucifer (Spring Peeper)

Where found: There are two subspecies of the spring peeper, the northern (P. c. crucifer) and the southern spring peeper (P. c. bartramiana). The northern is similar to the southern except for a strong dark marking on the southern frog's belly. The southern spring peeper is limited to northern Florida and southern Georgia, while the northern can be found all over the east of the USA and eastern Canada.

Description: The spring peeper is a small frog, attaining an adult size between 0.75 and 1.5 inches (up to 40mm) long. They have a dark cross on their backs roughly in the shape of an "X", though sometimes the marking may be indistinct. The color variations of the spring peeper are mostly tan, brown, olive green, or gray. Females are lighter-colored, while males are slightly smaller and usually have dark throats. Spring peepers are nocturnal frogs, so they are mostly heard but not seen. And they are especially easy to hear due to their extremely loud mating call which gives them the name "peeper".

Lithobates sylvaticus (Wood Frog)

Where found: Wood Frogs are found from northern Georgia and in isolated colonies in the central highlands in the eastern to central parts of Alabama, up through the northeastern United States, and all the way across Canada into Alaska. It is the most widely distributed frog in Alaska. They can be found from southeastern Alaska to north of the Brooks Range.

Description: Wood Frog is the common name given to Lithobates sylvaticus, previously Rana sylvatica. They are the only frogs found north of the Arctic Circle. In winter, as much as 35-45% of the frog's body may freeze, and turn to ice. Ice crystals form beneath the skin and become interspersed among the body's skeletal muscles. During the freeze the frog's breathing, blood flow, and heartbeat cease. Freezing is made possible by specialized proteins, glucose and perhaps accumulation of urea, which prevent intracellular freezing and dehydration. Wood Frogs primarily breed in ephemeral pools rather than permanent water bodies such as ponds or lakes. Adults emerge from hibernation in early spring and migrate to nearby pools. There, males chorus (a quacking sound) and mating occurs. Adult Wood Frogs spend summer months in moist woodlands, forested swamps, and bogs where they forage and maintain body moisture as surrounding environments dry out. Females' eggs are formed by late fall. By late fall or early winter, they leave forested swamps and travel to neighboring uplands to overwinter. Some may remain in moist areas to overwinter. They tend to hibernate in the upper organic layers of the soil, under leaf litter, and in close proximity to breeding pools.

Rana (Leopard Frog)

Where found: Once abundant in North America and Canada, their population has declined in recent years because of pollution and deforestation. Leopard frogs are often used as environmental indicator species because of their heightened sensitivity to chemical pollutants found in the air and water.

Description: Leopard frogs, which are also called meadow frogs and grass frogs, are a collection of so-called true frog within the genus Rana. They are commonly used as dissection specimens in biology classrooms. Leopard frogs are recognized by their green or brown coloration with distinct light-edged dark spots across the back and white underside. They also have a characteristic line of raised glandular skin extending from each eye to the groin.

Pseudacris regilla (Pacific Chorus Frog)

Where found: The Pacific Chorus Frog, formerly the Pacific Tree Frog (Hyla regilla) is a species of chorus frog native to the pacific coast of North America from Baja California in Mexico, through the states of California, Oregon, Washington (it is the Washington state frog), and into Canada and extreme southern Alaska. It ranges east into Nevada and Idaho.

Description: This is probably the most commonly heard and encountered frog in California and its call is often heard as a nighttime background sound in Hollywood movies. The Pacific tree frog can reach up to about 5 cm in length. The males are often smaller than the females. These frogs can have highly variable color on their bodies anywhere from gray, brown, tan or bright green and can even change between them. They are usually a pale or white color on their bellies. They have many variations of markings on their back and sides that are usually dark and spotty. The one identifiable mark is a dark stripe that goes over the eye from the nose to the shoulder. Their skin is covered in small bumps. They have long legs compared to their bodies and they tend to be slender. Their toes are long and are only very slightly webbed. On the end of each toe, there is a round sticky pad that is used for climbing and sticking to surfaces.

Litoria caerulea (Australian Green Tree Frog)

Where found: The Australian Green Tree Frog, simply Green Tree Frog in Australia, White's Tree Frog, or Dumpy Tree Frog (Litoria caerulea) is a species of tree frog native to Australia and New Guinea, with introduced populations in New Zealand and the United States.

Description: The Green Tree Frog can grow up to 10 centimeters (4 inches) in length. Its color depends on the temperature and color of the environment, ranging from brown to green; the ventral surface is white. The frog occasionally has small, white, irregularly shaped spots on its back, up to five millimeters in diameter, which increase in number with age.

Cryptobranchus alleganiensis (Eastern Hellbender)

Where found: The range of the Eastern Hellbender (C. a. alleganiensis) in North America extends from southwestern and south central New York, west to southern Illinois, and south to extreme northeastern Mississippi and the northern parts of Alabama and Georgia. A disjunct population occurs in east-central Missouri. The Ozark Hellbender (C. a. bishopi) subspecies exists as a disjunct population in southeastern Missouri and adjacent northwest Arkansas. Hellbenders are considered endangered in Illinois, Indiana, Maryland, and Ohio and rare or of "special concern" in Georgia, New York, North Carolina and Virginia.

Description: The Hellbender is a large aquatic salamander native to North America whose habitat includes large, swiftly flowing streams with rocky bottoms. Common names include the "snot otter" and "devil dog." Hellbenders have a flat body and head, with small eyes. Like all salamanders, they have short legs and thin bodies. Their tails, however, are especially keeled to help propel them through water. They have four toes on their front legs and five on their back ones.

Necturus maculosus (Common Mudpuppy)

Where found: The Common Mudpuppy is a species of aquatic salamander found throughout the northeastern United States, and parts of Canada.

Description: Mudpuppies prefer shallow water with lots of places to hide, but have been found at depths of up to 90 feet. The mating season is late autumn however eggs are not laid until late spring when 50 to 100 eggs are deposited in a nest cavity under a rock or other object. It takes 1 to 2 months for the eggs to hatch and 4 to 6 years for the young to reach maturity. Mudpuppies may live for up to 20 years. The common mudpuppy is nocturnal, but can be active in the day in muddy or weed-choked waters. It is carnivorous and feeds on fish, fish eggs, crayfish, insects, and molluscs.

Siren intermedia (Lesser Siren)

Where found: The Lesser Siren is found in the United States, primarily from Virginia to Florida, and west to Texas (ranging into northeastern Mexico as far as Vera Cruz), and north to Illinois, Indiana and Michigan.

Description: The Lesser Siren appears distinctly eel-like, with an elongated body, 7-26 inches (18-68 cm) in length. They have a pair of greatly reduced front legs, but no back legs. Their head is flattened and blunt with feather-like external gills on each side. They vary in color, from olive green to black, sometimes with darker colored speckling. The Lesser Siren is nocturnal, spending its days hidden in the debris and mud at the bottom of slow moving bodies of water. They feed primarily on aquatic invertebrates, including various kinds of worms, snails, and crustaceans. They will also eat the tadpoles and eggs of other amphibians.

Pseudobranchus striatus (Northern Dwarf Siren)

Where found: South-eastern United States

Description: The Northern Dwarf Sirenis a salamander lacking hind legs. It retains its gills into adulthood.

6. Describe the life history of some amphibian.[edit]


The life cycle of frogs, like that of other amphibians, consists of four main stages: egg, tadpole, metamorphosis and adult. The reliance of frogs on an aquatic environment for the egg and tadpole stages gives rise to a variety of breeding behaviours that include the well-known mating calls used by the males of most species to attract females to the bodies of water that they have chosen for breeding. Some frogs also look after their eggs—and in some cases even the tadpoles—for some time after laying.

The life cycle of a frog starts with an egg. Eggs are generally laid in water, and an individual female may lay egg masses containing thousands of eggs. While the length of the egg stage depends on the species and environmental conditions, aquatic eggs generally hatch within one week.

Some frogs do not have the tadpole stage going from egg to adult shape e.g. New Zealand's native frogs (pepeketua) belong to the genus Leiopelma. Eggs hatch and continue life as tadpoles (occasionally known as polliwogs). Tadpoles are aquatic, lack front and hind legs, and have gills for brething and tails with fins for swimming. Tadpoles are typically herbivorous, feeding mostly on algae, including diatoms that are filtered from the water through the gills. Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles and fish. The tadpole stage may be as short as a week, or tadpoles may overwinter and metamorphosis the following year in some species, such as the Midwife toad (Alytes obstetricans) and the Common Spadefoot (Pelobates fuscus).

At the end of the tadpole stage, frogs undergo metamorphosis, in which they transition into adult form. Metamorphosis involves a dramatic transformation of body shape and function, as tadpoles develop hind legs and then front legs, lose their gills and develop lungs. Their intestines shorten as they shift from an herbivorous to a carnivorous diet. The final stage of development from froglet to adult frog involves the loss of the tail.

After metamorphosis, young adults may leave the water and disperse into terrestrial habitats, or continue to live in the aquatic habitat as adults. Almost all species of frogs are carnivores as adults, eating invertebrates such as spiders, insects, snails, and slugs. A few of the larger species may eat prey such as small mammals, fish and smaller frogs. Some frogs use their sticky tongues to catch fast-moving prey, while others capture their prey and force it into their mouths with their hands. However, there are a very few species of frogs that primarily eat plants. Adult frogs are themselves preyed upon by birds, large fish, snakes, otters, foxes, badgers, coatis, and other animals.

7. Explain the economic value of amphibians.[edit]

Amphibians are insect eaters, so they are very valuable for controlling mosquito populations. They are also the preferred dinner for several mammal, bird, fish, and reptile species.

Amphibians are valuable for medical research. They are raised and sold to research institutions.

The larvae of newts and salamanders are sold as fish bait.

Amphibians are closely monitored by ecologists, because they are among the first animals affected by environmental problems such as pollution and the destruction of the ozone layer.

8. Where do toads spend the winter or dry season?[edit]

Toads burrow below the frost line and hibernate for the winter. Plant matter actually generates a bit of heat as it decays, so toads prefer areas with plenty of leaf litter and fallen logs.

9. Identify two species of frogs by their sound or imitate the sounds of two different species of frogs.[edit]

Here are the calls of three frogs.

European toad (Bufo bufo)
Spring Peeper (Pseudacris crucifer)
Big-eyed Tree Frog (Leptopelis vermiculatus)

For more frog calls, Smithsonian Folkways Recordings has several frog calls available on CD or for download.

10. How do frogs and toads sing? What makes the noise so loud?[edit]

Frogs call by passing air through the larynx in the throat. In most calling frogs, the sound is amplified by one or more vocal sacs, membranes of skin under the throat or on the corner of the mouth that bulge out during the amplification of the call.

Some frogs lack vocal sacs, but these species can still produce a loud call. Their mouths are enlarged and dome-shaped, acting as a resonance chamber that amplifies their call. The body of a guitar does much the same thing, having a large hollow section that causes the sound to resonate inside before escaping to the outside atmosphere.

11. Do one of the following[edit]

In the 1990's, amphibian populations in the United States and Canada began a precipitous and mysterious decline. Many frogs were discovered in Minnesota with unexplained deformities, including extra limbs, missing limbs, deformed limbs, and missing eyes. As a result, many species of amphibians are now protected by state and federal laws. When observing wild amphibians, it is extremely important that they not be handled. Doing so can spread disease to these creatures, causing further decline. Before venturing out, make sure your Pathfinders understand and appreciate the danger facing amphibians today. Do not allow your group to capture or otherwise harass them, and do not destroy their environment. Rather than pursuing the two options (a and b) listed for this requirement, it may be wiser to substitute an alternate requirement. One possibility is to have your Pathfinders research the amphibian population crash.

a. Observe a toad in your yard or neighborhood to find out.(1) Where and when it sleeps,(2) When it leaves its home for food,(3) How fast it can travel,(4) How far it can jump, and as many other interesting things as you can find out about it, and write an essay covering the details requested in the first section of this question.[edit]

It is recommended that instead of investigating wild amphibians, the student should research them using other available resources, including the Internet, books, and encyclopedias. It is recognized that observing them in the wild is by far more fascinating, but it also carries the potential to do great harm to the amphibian population. See the notes in section b for more details.

b. Hatch some amphibian eggs and watch them through their growth cycle and write an essay covering the details.[edit]

Frog eggs can be purchased from - but only in the spring.

According to Field Guide of Amphibian Larvae and Eggs of Minnesota, Wisconsin, and Iowa, a publication of the U.S. Geological Survey (USGS), "State and federal laws protect amphibians from exploitation. Collection permits are required from the appropriate state or federal authorities before capturing, handling, or collecting amphibians."

It is therefore recommended that you not attempt to collect amphibian eggs on your own. You can download this book as a PDF from the page cited above. Even if you do not live in Minnesota, Wisconsin, or Iowa, the species covered in this book may be indigenous to your area.

The USGS publication further states, "To prevent the spread of disease to native populations, any frogs or salamanders you raise should not be released back into the environment. Lab-raised amphibians can be anesthetized and euthanized with benzocaine or tricaine methanesulfonate (MS 222, Green 2001). If you anticipate difficulty complying with this guidance, you should not undertake raising larvae in captivity."



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