On the Post-larval Stage of Plagusia depressa tuberculata LAMARCK(GRAPSIDAE)

Abstract

Two living specimens of megalopa of P. depressa tuberculata LAMARCK were obtained at the coast of Manazuru, Sagami Bay, in early autumn of 1963 and also in early summer of 1964, and were reared in the aquarium until they reach the first crab stage. These specimens have been compared with those of P. dentipes DE HAAN. The data is summarized in the following. The megalopa stage: a) The carapace is sparingly covered with a fine tomentum, whereas, it is naked P. dentipes. B) The rostrum is well projecting forwards and bified at the tip, whereas, it is rather short and broadly bilobed in P. dentipes. C) The exopod of the external maxilliped is composed of one segment, it is two-segmented in P. dentipes. D) The difference in number of plumose setae in the exopod of the last pleopod between these two species is shown in table 1. The first crab-stage: Aside from the various morphological points of difference between the young crabs of the two species, the carapace of P. depressa tuberculata is covered with tubercles and short hairs, whereas, it is not tuberculated but only haired in P. dentipes.