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''Mysticarion porrectus'', also known as ''Helicarion porrectus'', is a tree-dwelling snail in the family Helicarionidae. It is endemic to Australia. This species occurs in and near rainforests at high altitude in eastern Australia. It is associated with Gondwana cool temperate rainforests, with trees such as Antarctic Beech, Sassafras and Pinkwood. ''Mysticarion porrectus'' is found between Mount Dromedary in south east New South Wales up the Great Dividing Range to Mount Superbus, 150 km south west of Brisbane, Queensland == Description == The shell of this snail species is very thin and transparent, so the brightly coloured internal organs are visible through it. The animal has a gland at the end of its tail which is thought to emit pheromones during courtship. The shell of this ''Mysticarion'' species is too small for the soft parts to completely retract into. This gastropod is what is referred to as a "semi-slug": through the course of evolution, the shell has become reduced in size and thickness so that now it mainly offers some protection to the visceral organs. This phenomenon of shell reduction has occurred independently across a number of different families. In some families such as the Athoracophoridae, Cystopeltidae and Limacidae the shell has either completely disappeared or has been so reduced in size as to become a small internal plate – these animals are known as slugs, which are simply snails that have lost their external shell through the course of evolution. It is thought that shell reduction in some families has occurred because of a shortage in calcium carbonate in the local rocks or soil; this calcium carbonate is needed by snails to manufacture their shells. In the Helicarionidae, shell types range across almost the whole spectrum, from species with large, fully formed shells they can withdraw back into, to those with very reduced ear-shaped or plate-like shells that are partly or almost completely internal, and which sit on their backs like a saddle. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mysticarion porrectus」の詳細全文を読む スポンサード リンク
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