Red crab - Red crab

This crab belongs to the order Decapoda, class Crustacea, family Portunidae. Its carapace is about 7 cm wide. It is widely distributed from the coast of the Boso Peninsula through various parts of the Western Pacific Ocean to the western Indian Ocean. It lives from rocky reefs to depths of about 30 meters, and is often caught in gill nets set for spiny lobsters. Its carapace is densely covered with soft short hairs. It has six broad teeth on its calyx and five teeth on the front edge of its carapace, but the fourth tooth on the front edge is very small. Its claws are powerful, and the lower edge of its palm is lined with numerous rows of granules, giving it a scaly appearance. Its color is a uniform purple-blackish brown, but its forehead and front edges are bordered with crimson red. T. sima , which has a forehead divided into two lobes, is often found among the seaweed on the rocky reefs. This crab has a carapace width of 4 cm and swims away quickly.

[Masamichi Takeda]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

節足動物門甲殻綱十脚(じっきゃく)目ワタリガニ科に属するカニ。甲幅7センチメートルほどになる。房総半島沿岸から西太平洋各地を経てインド洋西部まで広く分布する。岩礁から水深30メートルくらいまでにすみ、イセエビ用の刺網によくかかる。甲は軟らかい短毛で密に覆われている。額(がく)には幅広い6歯、甲の前側縁には5歯あるが、前側縁の第4歯はごく小さい。はさみ脚(あし)は強大で、掌部の下縁では顆粒(かりゅう)が多数の列をなして鱗(うろこ)状を呈する。じみな紫黒褐色であるが、額や前側縁は紅赤色で縁どられている。岩礁の海藻の間には額が2葉に分かれただけのフタバベニツケガニT. simaが多い。このカニは甲幅4センチメートルで、すばやく泳いで逃げる。

［武田正倫］

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