Kikunohanagai - siphon shell

A shell of the family Polypodidae in the class Gastropoda of the phylum Mollusca. It is found throughout Japan from the Boso Peninsula to Okinawa, and also on the Korean Peninsula, where it attaches to rocky reefs in the intertidal zone. It has a low, cap-shaped shell with a shell height of 6 mm, a shell opening length of 30 mm, and a shell opening diameter of about 25 mm. The shell surface is black, and there are 7 to 10 white radial ribs from the apex, which are clearly visible on the inside. One of the ribs protruding from the front right is particularly thicker than the others. It normally lives in a fixed location, and when the tide goes out, it goes out to forage for food a few to 10 centimeters away, and has a homing habit of returning to its original location by following the path it took before the water dries up. In summer, it lays ring-shaped, gelatinous egg masses on rocks.

[Takashi Okutani]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

軟体動物門腹足綱コウダカカラマツガイ科の貝。房総半島から沖縄までの日本各地と朝鮮半島にも分布し、潮間帯の岩礁に付着している。殻高6ミリメートル、殻口長30ミリメートル、殻口径25ミリメートルぐらいの低い笠(かさ)形で、殻表は黒く、殻頂から7～10本の白い放射肋(ろく)があり、内面ではそれが明瞭(めいりょう)である。右前方に出る1本はとくに他のものよりいくらか太い。平常は一定の場所にすみ、潮が引いてくるとそこから数センチメートルないし十数センチメートルの距離に餌(えさ)をあさりに出て、干上がるまでにきた道に沿って元の所に帰る帰家習性がある。夏には岩上に指輪状でゼラチン質の卵塊を産む。

［奥谷喬司］

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