REPRODUCTIVE PROCESSES REVEALED BY SPERMATOPHORE DEHISCENCE EXPERIMENTS AND BY HISTOLOGY, ULTRASTRUCTURE, AND HISTOCHEMISTRY OF THE FEMALE REPRODUCTIVE-SYSTEM IN THE SNOW CRAB CHIONOECETES-OPILIO (O-FABRICIUS)

Histological, histochemical, ultrastructural, and microbiological techniques were used to elucidate the structure and function of the female reproductive system in the snow crab Chionoecetes opilio (O. Fabricius). The anatomy of the ovary and oviduct conform to that of other brachyuran species. The spermatheca comprises a dorsal (glandular) and a ventral (chitin-lined) region, with no intervening anatomical separation. Ultrastructural and histochemical bases are presented for the dual role of the spermatheca in secretion and sperm storage. Proteinaceous polysaccharides are the dominant holocrine secretion of the glandular epithelium. A dense, morphologically homogeneous bacterial population was observed in the spermathecae of all of 25 crabs examined. A discrete layer of nonspermatophore-containing acid mucopolysaccharides appears to be transferred to the vagina and ventral spermatheca region by the male after insemination. A functional partitioning of spermatophores seems to occur at insemination; some dehisce immediately (probably due to mechanical forces), while those resisting initial dehiscence are stored in the spermatheca. In vitro experiments show that storage in the spermatheca greatly increases the tendency of spermatophores to dehisce when exposed to sea water. Functional correlates to these data are explored, with emphasis on roles and interactions of secretions, bacteria, spermatophore storage, and dehiscence, and mechanisms of ensuring last-male precedence under conditions of sperm competition.