Tadpole Facts
Tadpoles are the offspring of frogs, although the the term tadpole is also commonly meant to include the young of salamanders and newts. The term thus loosely encompasses all small organisms that resemble tadpoles. Tadpoles generally live in water until they grow legs, then living both on land and water.
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Frog Tadpoles
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Tadpoles are the immature frogs and toads that have not yet transformed into adult frog or toad forms. They have tails to enable them to move through the water in which they hatched from eggs. Sometimes the tail is large, wide and rounded at the end; in other species it is thin and ends like a filament. The main characteristic is that it functions like the tail of a fish as means of propulsion or forward movement. The tail, however, has no bones or cartilage in it whatsoever, since it will disappear in later stages. The head is generally bulbous, larger at the rear part which will later become the frog's body, and narrower at the forward end. The mouth is usually a small hole lined with very tiny teeth used to chew solid food such as detritus, decaying materials and algae.
History
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Tadpole fossils have been found in the Upper Miocene strata, preserved through biofilms, and the bone structure as carbon films. Some fossils are composed of calcium carbonate and calcium phosphate. It only means frogs had been existing ever since that time. For newer developments, tadpoles are being experimented on to detect polluted areas. Through bio-engineering, tadpoles have been made to glow green upon coming in contact with polluted water, the pollution even measured by shining on the tadpole a blue light-emitting diode. The level of fluorescence produced indicates the amount of pollution present in the area.
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Unusual Species
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In some species the tadpole's mouth has external barbels like those in the mouth of a catfish, used to feel for food, particularly the species Aglossal Xenopus. In others like the Megalophrys montana, the mouth is a funnel-like projection by which the tadpole anchors itself in upright position at the water surface. Some tadpole species are omnivorous --eating both plants and animals---and sometimes cannibalistic: they eat others of their kind, especially the plains spadefoot toads of New Mexico. A special species is remarkable in being transparent. These are the Malay and Indian Engystomatid species of the Callula and Microhyla genera.
Developmental Stages
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After bursting through their egg skins, tadpoles normally stick to plants using a certain part of their belly, while they consume their yolk sacs for nutrition. In about a week to ten days, they will start to swim freely and feed on tiny plants or algae. Before nine weeks are over most tadpoles have tiny hind legs showing and the head has elongated to a form similar to a frog's but the tail remains, though perhaps shorter. By the end of the third month from birth, the tadpole has become a froglet, a juvenile frog.
Predators
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Tadpoles have many predators and the odds of survival can be low. Predators include fish , larger frogs, newts, snails, birds, snakes, and crayfish. They fall relatively low on the food chain and are at risk of becoming the prey of any larger or carnivorous animal in their surrounding habitat.
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References
- Photo Credit les tétards image by Claudio Calcagno from Fotolia.com
