- See also: Caecilian, bishop of Carthage, 312 C.E.
The Caecilians are an order (Gymnophiona or Apoda) of amphibians which resemble worms or snakes. They mostly live hidden in the ground which makes them the least explored order of amphibians, and widely
unknown.
Anatomy
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.
Distribution
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.
Reproduction
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 metamorphed 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 oviduct, which are eaten by the fetus with special scraping teeth.
Origin of the name
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 Linnaeus, 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.
Taxonomy
Taxonomically the Caecilians are divided into 5 families. The species numbers have to be taken with care, as many of the
species are described after only one specimen. Probably not all species have been described yet, however some of the described
different species might turn out to be normal variations inside one species.
Misc
Large Caecilians dubbed "ingots" plagued the French occupation of Indochina in
the years before the Vietnam war. The creatures were reported to borrow large holes and disrupt troop movement.
References
External links
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