Reproduction and embryonic diapause in the hermit crab Pagurus nigrofascia

Abstract

Vertical distribution and reproductive biology of the hermit crab Pagurus nigrofascia were researched from March 2003 to February 2005 along an intertidal boulder shore in Fukuoka, a warm temperate region of Japan. In the spring, P. nigrofascia was widely distributed throughout the intertidal area but moved to the upper intertidal area in the summer and to the middle intertidal area in the autumn. In the winter, most crabs were found in the lower intertidal area, as many had moved into the subtidal area. Most females produced a brood in March and released larvae in December after an extremely long incubation period of 9 months. From March to October, the embryos were in diapause, and the eggs were completely filled with yolk. In November, all embryos began to develop, and most broods hatched in December. New recruits appeared in March and April and grew slowly. These reproductive characteristics of P. nigrofascia were similar to those observed in a previous study in Hakodate, a cold temperate region of Japan. However, in Fukuoka, brood production and larval release occurred approximately 2 months earlier and females exhibited higher fecundity than in Hakodate.