Sperm polymorphism within the sea urchin Strongylocentrotus droebachiensis: divergence between Pacific and Atlantic oceans.

The rapid evolution of traits related to fertilization such as sperm morphology may be pivotal in the evolution of reproductive barriers and speciation. The sea urchin Strongylocentrotus droebachiensis has a circumarctic distribution and shows substantial genetic subdivision between northeastern Atlantic populations and northwestern Atlantic and Pacific populations. Using transmission electron microscopy, we show here that sperm shape, size, and ultrastructure differ markedly among populations of S.

Carbohydrate-based species recognition in sea urchin fertilization: another avenue for speciation?

Spawning marine invertebrates are excellent models for studying fertilization and reproductive isolating mechanisms. To identify variation in the major steps in sea urchin gamete recognition, we studied sperm activation in three closely related sympatric Strongylocentrotus species. Sperm undergo acrosomal exocytosis upon contact with sulfated polysaccharides in the egg-jelly coat.