Identification and role of carbohydrates on the surface of gametes in the zebra mussel, Dreissena polymorpha.

The objective of this study is to identify surface carbohydrates on zebra mussel, Dreissena polymorpha, eggs and sperm and to analyze their potential role in fertilization. The lectins WGA, Con A, LcH, LTA, SBA, PNA, and GSII were tested for affinity to both eggs and sperm. WGA, Con A, and LcH uniformly labeled eggs. LTA, SBA, PNA, and GSII did not. WGA labeled the entire sperm surface including the unreacted acrosome. Labeling by Con A, LcH, LTA, SBA, PNA, and GSII was restricted to the inner acrosomal region of acrosome-reacted sperm. GSII labeling suggests the presence of N-acetyl-d-glucosamine (GlcNAc) only in the inner acrosomal membrane and not on eggs. GlcNAc blocked sperm-egg binding. GSII labeling was associated with a ring-like structure at the site of sperm entry intimately associated with sperm-egg binding. Nonfertilizing sperm were detached from the egg surface along with the GSII basal ring about 15 min postinsemination in a process blocked by trypsin inhibitors.