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| Caecilians | ||||||||
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Rhinatrematidae Ichthyophiidae Uraeotyphlidae Scolecomorphidae Caeciliidae
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Caecilians' feet have degenerated, making the smaller species resemble worms, while the larger species with lengths up to 1.5 m resemble snakes. The tail is also very short, so the cloaca is near the end of the body. Their skin is smooth and usually dark-matt, but many species also have colorful skins. Inside the skin are calcite scales, which suggests that they are related with the fossil Stegocephalia . However the scales are now believed to be a secondary development, and not directly inherited from Stegocephalia. Due to their underground life the eyes are small and covered by skin for protection, which have led to the misconception that they are blind. However due to the skin cover their visual sense is limited to simple dark-light perception. All Caecilians share two tentacles at their head, which are probably used for the olfactory sense additional to the normal nose.
Except one lungless species - Typhlonectes eiselti, only known from one specimen collected somewhere in South America - all Caecilians have lungs, but also use the skin or the mouth for oxygen absorption. Often the left lung is much smaller than the right one, an adaptation to the body shape also found in snakes.
Caecilians are found in most of the tropic areas of South-East Asia, Africa and South America, except the dry areas and the high mountains. In South America their distribution extends well into the temperate north of Argentina. For central Africa no systematic search has been done yet, but it is likely Caecilians are found all over the tropical rainforest there.
Caecilians are the only order of amphibians which only use internal insemination. The male Caecilians have a penis-like organ, the phallodeum, which is inserted into the cloaca of the female for 2 to 3 hours. About 25% of the species are oviparous, the eggs are guarded by the female. For some species the young Caecilians are already metamorphedMetamorphosis in biology is physical development of the individual after birth or hatching involving significant change in form as well as growth and differentiation. It usually accompanies a change of habitat or of habits but may occur without such chang when they hatch, other hatch as larvae. The larvae aren't fully aquatic, but spend the daytime in the soil near the water.
75% of the species are viviparous, that means they give birth to already developed offspring. The fetus is fed inside the female with special cells of the oviductIn oviparous animals (those that lay eggs), the passage from the ovaries to the outside of the body is known as the oviduct . The eggs travel along the oviduct. In mammals, which evolved from reptiles, the oviduct turned into the Fallopian tubes, the uter, which are eaten by the fetus with special scraping teeth.
The name Caecilian derives from the Latin word caecus = blind, referring to the small or sometimes non-existing eyes. The name dates back to the taxonomic name of the first species described by Carolus LinnaeusCarolus Linnaeus (later, Carl von Linn ( May 23, 1707 January 10, 1778) was a Swedish scientist who laid the foundations for the modern scheme of taxonomy. He is also considered one of the fathers of modern ecology (see History of ecology). Biography Carl, which he gave the name Caecilia tentaculata. The taxonomic name of the order derives from the Greek words gymnos = naked and ophio = snake, as the Caecilians were originally thought to be related with snakes.
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