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The term ''ramshorn snail'' is used in two different ways. In the aquarium trade it is used to describe various kinds of freshwater snails whose shells are planispiral, meaning that the shell is a flat coil. Such shells resemble a coil of rope, or (as the name suggests) a ram's horn. In a more general natural history context, the term "ramshorn snails" is used more precisely to mean those aquatic pulmonate gastropod mollusks in the family Planorbidae that have planispiral coiled shells. This article is about ramshorn snails in the aquarium trade. For more information on the Planorbidae, see the article Planorbidae. Ramshorn snails have been bred for the aquarium trade and various color forms have been selected. Most of the aquarium ramshorn snails are species in the family ''Planorbidae'', but one kind is from a totally different family, the ''Ampullariidae''. Ramshorn snails can sometimes become a nuisance in an aquarium, because some of them breed so profusely. ==Description== Most of these snails are of the family Planorbidae, and they include the species ''Planorbarius corneus''. There are two different coloured skin forms: black and red; the latter lack the dark skin pigment melanin and consequently have a bright reddish skin, which is the colour of their blood. Interestingly their blood contains red hemoglobin, unlike other snails' blood, which contains greenish hemocyanin. These ramshorn snails breathe air. Although most of them are extremely small, some may reach a size of two and a half centimeters (one inch). The shells range from translucent through various shades of brown to a dark, nearly black color. The dark color appears to originate from dietary materials not generally available in the home aquarium, although many varieties from ponds are this dark shade. Snails of this family are spiralled sinistrally, with the opening hole slanted downward toward the right. Large folds of skin may protrude out of the more open left side. Like all air-breathing water snails, the animal has no operculum, and has only one pair of tentacles with the eye spots at the base of the tentacles. They lay eggs in globules, which tend to be brownish in color. The globules contain about a dozen or so eggs, though it can vary. The globules are translucent, so it is possible to visually see the new snails develop in size. The newborn snails are clearish white. 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「Ramshorn snail」の詳細全文を読む スポンサード リンク
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