2 EXTRACELLULAR MATRICES FROM OOCYTES OF THE MARINE SHRIMP SICYONIA-INGENTIS THAT INDEPENDENTLY MEDIATE ONLY PRIMARY OR SECONDARY SPERM BINDING

During spawning, female Sicyonia ingentis simultaneously release ova a nd stored nonmotile sperm and mix them externally to initiate gamete i nteraction. Sperm bind to a thin vitelline envelope (VE) via their ant erior appendage and within seconds are induced to undergo acrosomal ex ocytosis. The sperm penetrate the VE and become secondarily bound to t he surface coat (SC), a glycocalyx on the oocyte surface. In this stud y, both extracellular matrices were isolated from S. ingentis oocytes. Isolated VEs mediated only primary sperm binding (i.e., before the ac rosome reaction), while the isolated SCs mediated only secondary sperm binding (i.e., after acrosomal exocytosis). Isolated S. ingentis VEs were used to characterize primary sperm binding activity. The two extr acellular matrices differ morphologically and possess different polype ptide profiles. Soluble fractions of isolated VEs inhibited primary sp erm binding in a concentration dependent manner, and immunolocalizatio n of VE components demonstrated highly localized VE binding sites al t he tip of the sperm anterior appendage by which sperm bind eggs. Exten sive Pronase digestion of VE components did not affect sperm binding a ctivity of solubilized VE components, while complete deglycosylation w ith trifluoromethanesulfonic acid destroyed sperm binding activity. Ho wever, neither alkaline treatment nor enzyme digestion using glycosida ses specific for asparagine and serine/threonine linked oligosaccharid es affected sperm binding activity.