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.

Genetic evidence of postglacial population expansion in Puget Sound rockfish (Sebastes emphaeus).

Several rockfish species (genus Sebastes) along the northeastern Pacific Ocean have rapidly declined in abundance owing in part to overfishing. A striking exception is the dwarf-like Puget Sound rockfish Sebastes emphaeus, whose densities have increased by several orders of magnitude over the last several decades. To describe their genetic structure, we sequenced 395 bp from the mitochondrial control region of 128 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.

Phylogeny and development of marine model species: strongylocentrotid sea urchins.

The phylogenetic relationships of ten strongy-locentrotid sea urchin species were determined using mitochondrial DNA sequences. This phylogeny provides a backdrop for the evolutionary history of one of the most studied groups of sea urchins. Our phylogeny indicates that a major revision of this group is in order.

Sulfated fucans from the egg jellies of the closely related sea urchins Strongylocentrotus droebachiensis and Strongylocentrotus pallidus ensure species-specific fertilization.

Sulfated polysaccharides from egg jelly are the molecules responsible for inducing the sperm acrosome reaction in sea urchins. This is an obligatory event for sperm binding to, and fusion with, the egg. The sulfated polysaccharides from sea urchins have simple, well defined repeating structures, and each species represents a particular pattern of sulfate substitution.