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The family Mormyridae, sometimes called "elephantfish" (more properly freshwater elephantfish), are freshwater fish in the order Osteoglossiformes native to Africa. It is by far the largest family in the order with around 200 species. Members of the family are popular, if challenging, aquarium species. These fish are also known for having large brain size and unusually high intelligence. They are not to be confused with the marine and brackish water callorhinchid elephantfish (family Callorhinchidae) of south hemisphere oceans. ==Description and biology== The elephantfishes are a diverse family, with a wide range of different sizes and shapes. The smallest are just in adult length, while the largest reach up to . They do, however, have a number of unique features in common. Firstly, the cerebellum (part of the brain) is greatly enlarged, giving them a brain to body size ratio similar to that of humans (though other sources give the brain/body proportion as 'similar to that of birds and marsupials'; Helfman, Collette & Facey 1997, p. 191). This is likely to be related to the interpretation of bio-electrical signals. Secondly, the semicircular canals in the inner ear have an unusual structure and are associated with a gas-filled bladder entirely separate from the main swim bladder. Some species possess modifications of the mouthparts to facilitate feeding upon small invertebrates buried in muddy substrates. The shape and structure of these leads to the popular name of "elephant nosed fish" for those species with particularly prominent mouth extensions. The extensions to the mouthparts usually consist of a fleshy elongation attached to the lower jaw. They are flexible, and equipped with touch, and possibly taste, sensors. Their mouths are non-protrusible, and their head (including the eyes), the dorsum and belly are covered by a thin layer of skin that is perforated with small pores leading to electroreceptors. Only a single gonad is present, located on the left side of their body.〔(Communication Behavior and Sensory Mechanisms in Weakly Electric Fishes )〕 Mormyridae and their close relative Gymnarchus are also unique in being the only vertebrates where the male sperm cell doesn't have a flagellum.〔(Mormyridae | Mormyridae - African weakly electric fishes )〕 Among those members of the family lacking extended mouthparts, the body shape and general morphology of the fishes has led to some being known among aquarists by the name of "baby whale", despite the fact that true whales are mammals. Other "mormyrid mammalian misnomers" include the term "dolphin fishes", in reference to certain members of the Genus ''Mormyrops''. 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「Mormyridae」の詳細全文を読む スポンサード リンク
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