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The western mosquitofish (''Gambusia affinis'') is a species of freshwater fish, also known commonly, if ambiguously, as simply mosquitofish or by its generic name, ''Gambusia'', or by the common name gambezi. There is also an eastern mosquitofish (''G. holbrooki''). Mosquitofish are small in comparison to many other freshwater fish, with females reaching an overall length of and males at a length of . The female can be distinguished from the male by her larger size and a gravid spot at the posterior of her abdomen. The name "mosquitofish" was given because the diet of this fish sometimes consists of large numbers of mosquito larvae, relative to body size.〔 Gambusia typically eat zooplankton, beetles, mayflies, caddisflies, mites, and other invertebrates; mosquito larvae make up only a small portion of their diet.〔Lund, Mark (16 November 2005). (Mosquitofish: Friend or Foe? ) Edith Cowan University.〕 Mosquitofish were introduced directly into ecosystems in many parts of the world as a biocontrol to lower mosquito populations which in turn negatively affected many other species in each distinct bioregion. Mosquitofish in Australia are classified as a noxious pest and may have exacerbated the mosquito problem in many areas by outcompeting native invertebrate predators of mosquito larvae. Several counties in California distribute mosquitofish at no charge to residents with manmade fish ponds and pools as part of their mosquito abatement programs.〔Alameda County Mosquito Abatement Program http://www.mosquitoes.org〕〔(Mosquitofish ). Santa Clara County Vector Control District〕〔Contra Costa County Mosquito and Vector Control District http://www.contracostamosquito.com/〕 The fish are made available to residents only and are intended to be used solely on their own property, not introduced into natural habitat. On 24 February 2014, Chennai Corporation introduced western mosquitofish in 660 ponds to control the mosquito population in freshwater bodies.〔(Mosquitofish to fight mosquito breeding in Chennai, India )〕 Fertilization is internal; the male secretes milt into the genital aperture of the female through his gonopodium.〔〔 Within 16 to 28 days after mating, the female gives birth to about 60 young.〔〔 The males reach sexual maturity within 43 to 62 days. The females, if born early in the reproductive season, reach sexual maturity within 21 to 28 days; females born later in the season reach sexual maturity in six to seven months.〔 ==Description== Mosquitofish are small and of a dull grey coloring, with a large abdomen, and have rounded dorsal and caudal fins and an upturned mouth.〔 Sexual dimorphism is pronounced; mature females reach a maximum overall length of , while males reach only . Sexual dimorphism is also seen in the physiological structures of the body. The anal fins on adult females resemble the dorsal fins, while the anal fins of adult males are pointed. This pointed fin, referred to as a gonopodium, is used to deposit milt inside the female. Adult female mosquitofish can be identified by a gravid spot they possess on the posterior of their abdomens. Other species considered similar to ''G. affinis'' include ''Poecilia latipinna'', ''Poecilia reticulata'', and ''Xiphophorus maculatus''; it is commonly misidentified as the eastern mosquitofish.〔〔(【引用サイトリンク】url=http://www.issg.org/database/species/ecology.asp?fr=1&si=126 )〕 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「Mosquitofish」の詳細全文を読む スポンサード リンク
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