无足目
维基百科，自由的百科全书
- See also: Caecilian, bishop of Carthage, 312 C.E.
| 无足目 | ||||||||
|---|---|---|---|---|---|---|---|---|
 caecilian |
||||||||
| 分类 | ||||||||
|
||||||||
| Families | ||||||||
|
吻蚓科 |
无足目又稱為蚓螈目(Gymnophiona or Apoda) 是两栖动物中看起來最像蟲或是蛇的一類. 大部分的無足目均棲息於地下，因此無足目是兩棲類中發現種類最少的。
目录 |
[编辑] 解剖
無足目的動物的腳已經退化，造成其中較小的種類看起來像蠕蟲，而比較大的種類（長度可到1.5公尺）則看起來像蛇。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 埃及伊蚊. 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.
除了在南非發現的Typhlonectes eiselti沒有肺之外，所有無足目的生物都有肺，但是他們同時也使用皮膚與口進行氧氣的吸收。通常為了適應身體的構造，左肺都比右肺小，相同的現象在蛇的構造裡也觀察得到。
[编辑] 分类
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.
[编辑] 繁殖
無足類是兩棲類中唯一進行體內受精的種類。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 母体发芽, 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.
[编辑] 名字的起源
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.
[编辑] 分类法
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, on the other hand some of the described different species might turn out to be normal variations inside one species.
- Beaked Caecilians (Rhinatrematidae) - 2 genera, 9 species
- Fish Caecilians (Ichthyophiidae) - 2 genera, 39 species
- Indian Caecilians (Uraeotyphlidae) - 1 genus, 5 species
- Tropical Caecilians (Scolecomorphidae) - 2 genera, 6 species
- Common Caecilians (Caeciliidae) - 26 genera, 107 species
[编辑] 其它
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.
[编辑] 参考
- Werner Himstedt, Die Blindwühlen, ISBN 3894324341 (German)
