ラスバンマメガニ Pinnixa rathbuni Sakai (短尾類, カクレガニ科)の後期幼生

概要

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Zoeae and Megalopae of P. rathbuni Sakai were collected by sub-surface towing of a plankton net under a fish-luring light near Hashirimizu in the mouth of Tokyo Bay, during the winter and spring seasons from 1971 to 1977. They were reared in the laboratory and their successive moultings were observed. In this zoea, the exopod of maxillipeds 1 and 2 bears 11 or 12 natatory setae; this characteristic seems to be a typical form of the fifth zoeal stage, and the larva resembles zoea of the so-called "Dissodactylozoea pinna" by Aikawa (1933) in many respects. The megalopa seems to resemble a juvenile crab, but the living megalopa usually swims very actively with the aid of the natatory pleopods of the abdomen. This larva developed into the first crab-stage during rearing. According to Faxon (1879) and Hyman (1924), the last zoea of P. sayana Stimpson develops directly into the first crab-stage. In both authors, figures of the first crab-stage, however, natatory pleopods of the abdomen are present, which is evidence of the megalopa stage, not the crab-stage.
1979-09-25