HARPER, F.M.; POMERLAU, E.A.; RAWSON, P.D.*; Rollins College; University of Maine, Orono; University of Maine, Orono: Species-specific egg-borne proteins in the blue mussels, Mytilus edulis and M. trossulus

Several gamete recognition systems have been recognized for their roles in conspecific fertilization and gamete compatibility in marine invertebrates. In blue mussels, divergence in the amino acid sequence of the sperm protein M7 lysin has been proposed as a partial barrier to heterospecific fertilization. Intraspecific variation in the compatibility of Mytilus edulis eggs to M. trossulus sperm suggests proteins other than just M7 lysin are involved. In a previous study comparing intraspecific and interspecific matings between these two species, some M. edulis eggs were receptive to M. trossulus sperm, while other M. edulis eggs were unreceptive. To investigate the maternal or egg effect on the interspecific gamete compatibility in M. edulis, we identified receptive and unreceptive M. edulis females in cross-fertilization studies. We then isolated and homogenized proteins from egg vitelline envelopes to identify egg-borne proteins potentially involved in gamete interactions. Proteins were separated on Bis-Tris gels and stained for glycoproteins and total proteins. Receptive M. edulis and M. trossulus females shared several glycoprotein bands, which were notably absent in the unreceptive M. edulis profiles. Two proteins bands appeared species-specific: a ~67,000 MW protein band unique to M. edulis and a ~70,000 MW protein band unique to M. trossulus. Vitelline envelopes from a field-collected hybrid female contained both protein bands. We will present our preliminary findings based on the results of LC-tandem MS analyses.