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pouched lamprey
The pouched lamprey (''Geotria australis'') also known as wide-mouthed lamprey, is the only species in genus ''Geotria'', which is in turn the only genus in the family Geotriidae. It is native to the southern hemisphere where it spends part of its life in the sea and part in freshwater where it returns to spawn and die.
==Description==
It is a species of lamprey that occurs throughout much of the southern hemisphere. It has a thin eel-like body up to long,〔Dianne J. Bray & Martin F. Gomon, 2011, Pouch Lamprey, Geotria australis, in Fishes of Australia, accessed 07 Oct 2014, http://www.fishesofaustralia.net.au/home/species/3415〕 with two low dorsal fins on the back half. Like other lampreys, it has no jaws, instead having a sucker. The skin is a striking silver in adult lampreys caught fresh from the sea but soon changes to brown after they have been in freshwater for some time, due to deposition of biliverdin. The freshwater ammocoetes or larvae stage of the life cycle are a dull brown in colour for most of their lives, changing to silver with blue-green stripes during their six-month metamorphosis into the adult stage, after which they migrate downstream to the sea. The central nervous system of the pouched lamprey develops notably during metamorphosis, with particularly large increases in the volume of visual areas of the brain. Adults' eyes are relatively small, and located on the side of the head. When fully mature, males develop a baggy pouch under their eyes, the function of which is unknown. However, there have been suggestions that the pouch in Northern hemisphere species has been used by males during breeding times for gathering stones to make a nest.〔(Pouch use )〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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