Guppy - Guppy (English spelling)

A tropical freshwater fish of the order Anserinidae and family Guppyidae. It is found in rivers in northern South America, Venezuela, Guiana, northern Brazil, Trinidad, and Barbados. It was introduced to Japan as an ornamental fish, and is widely used because it is easy to keep. It has also become wild in rivers in hot spring areas and the Ryukyu Islands. Females grow to 6 cm in length, while males only grow to 3 cm. Its body is slender and resembles that of a killifish. Females have a light brown body and a short tail, but males have a wide variety of body colors, large tails, and a variety of shapes and colors, so many beautiful varieties have been created. In addition, it has a strong reproductive ability, and if a male and female are placed in an aquarium with lush aquatic plants, mating will occur without special care, and the number of fry will increase.

The optimum water temperature for breeding is 22-24°C, but they are sensitive to low temperatures and cannot move at 17-18°C. They are ovoviviparous, so they are born looking similar to their parents. The male's anal fin is modified to become a copulatory leg (gonopodium), which sends sperm into the female's body for internal fertilization. Sperm are stored in the female's body for a long time, and one mating can result in multiple fertilizations. They are usually born once a month. The number of offspring varies depending on the size of the female, but the maximum number is over 150. Since there is a risk that the newly born fry will be eaten by other fish or the parents, they are isolated in a hatching tank or with a saran net. Since fry are born early in the morning, even if you only have one tank, you can simply scoop up the newly born fry that gather on the surface every morning and move them into an incubator (commercially available) floating in the tank. Once they reach 10 days of age, they will no longer be eaten by their parents, so they can be kept together. Their food consists of artificial solid food, brine shrimp (arthropod Artemia), and tubifex worms.

[Tetsuji Nakabo]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

硬骨魚綱トウゴロウイワシ目グッピー科の熱帯淡水魚。南アメリカ北部のベネズエラ、ギアナ、ブラジル北部、トリニダード島、バルバドス島に分布し、河川にすむ。日本には観賞用として移入され、飼いやすいので広く普及している。また、温泉地の川や琉球(りゅうきゅう)諸島などで野生化している。雌は体長6センチメートルになるが、雄は3センチメートルにしかならない。体は細長くメダカに似る。雌は体が淡褐色で尾も短いが、雄は体色も変異に富み、尾も大きく形や色彩もさまざまであるので、美しい品種が多くつくられている。また、繁殖力が強く、水草を繁茂させた水槽中に雌雄を入れておくと、特別に管理しなくても交尾が行われて仔魚(しぎょ)の数が増えてくる。

　飼育の適水温は22～24℃で、低温に弱く17～18℃になると活動できない。卵胎生なので親魚に似た姿で産まれる。雄の臀(しり)びれは変形して交接脚(きゃく)（ゴノポディウムgonopodium）となり、雌の体内に精子を送り込み体内受精を行う。精子は雌の体内に長期間蓄えられ、1回の交尾で数回受精させることができる。普通1か月に1回の割合で産出される。産仔(さんし)数は雌の大きさによって異なり、最大は150尾以上。生まれたての稚魚は他魚や親魚に食べられてしまうおそれがあるので、孵化(ふか)用の水槽や、サラン網などで隔離する。稚魚の産出は早朝に行われるので、水槽が1個しかない場合でも、毎朝、表面に集まった生まれたばかりの稚魚をすくって、水槽中に浮かせた孵化器（市販のもの）の中に移せばよい。生後数日から10日もたてば、親魚に食べられなくなるので、いっしょにしてもよい。餌(えさ)は人工固形餌料(じりょう)、ブラインシュリンプ（節足動物のアルテミア）やイトミミズなどである。

［中坊徹次］

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