REPRODUCTIVE-BIOLOGY OF COROPHIUM-VOLUTATOR AND COROPHIUM-ARENARIUM (CRUSTACEA, AMPHIPODA)

The life-cycles of C. volutator (Pallas) and C. arenarium Crawford in the Dovey Estuary [Wales, UK] are based on 2 generations/yr. Reproduction is well established by April and although the overwintering generation dies during the summer, reproduction continues until Oct. as a result of the breeding of summer-generation animals. The mean brood size of C. volutator is greater than that of C. arenarium and both species show high levels of egg loss from the brood pouch. Hatching and molting of the embryonic cuticle take place simultaneously and the initial rupture of the egg membranes is made by spines on the cuticle of the telson of the future free-living animal. These spines persist throughout post-embryonic life. Adult females of both species show a semi-lunar breeding rhythmicity and, associated with this, adult males show a rhythmic pattern of crawling behavior. As the tide ebbs during the rising spring tide period, adult males emerge from the sediment and crawl across the mud surface in search of burrows occupied by adult females. Copulation apparently takes place in the burrow and not in the water column.