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Diving bell spider
The diving bell spider or water spider (''Argyroneta aquatica'') is the only species of spider known to live almost entirely under water. It is the only member of the genus ''Argyroneta''. When out of the water, the spider ranges in colour from mid to dark brown, although the hairs on the abdomen give it a dark grey, velvet-like appearance. 〔(【引用サイトリンク】url=http://danmarks-edderkopper.dk/species-description?taxon=Argyroneta%20aquatica )〕
==Ecology==
''A. aquatica'' is found in freshwater ponds and streams in northern and central Europe and northern Asia up to latitude 62°N. As with other spiders it breathes air; when submerged an air bubble is trapped by a dense layer of hydrophobic hairs on its abdomen and legs, giving the abdomen a silvery appearance. The spider lives for about two years in captivity. 〔
''A. aquatica'' is able to remain submerged for prolonged periods of time due to the silk-based structure it constructs in order to retain an oxygen supply, named after the diving bell structure it resembles. The species range in size, although the size of females may be limited as they put more energy into building and maintaining their larger bells.〔 Males are typically more active than females and typically 30% larger. This size differential favoring males is unusual for spiders, where sexual dimorphism is usually in favour of larger females. Theories suggest that the male's more active hunting style requires greater strength to overcome water resistance and counteract the buoyancy of their mobile air supplies. This larger body size is also associated with longer front legs, shown to affect diving ability and giving the males superiority in diving over the more sessile females.〔
The spiders prey on aquatic insects and crustaceans such as mosquito larvae and ''Daphnia''. Their bite is quite painful as the fangs can pierce the skin, causing localised inflammation and feverishness.〔Ross Piper (2007), ''Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals'', Greenwood Press.〕 The spiders themselves fall prey to frogs and fish.〔(【引用サイトリンク】title=Water Spider )〕
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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