Ultrastructure and role of the lobster vas deferens in spermatophore formation: The proximal segment.

We have examined the anatomy of the vas deferens of the lobster Homarus americanus and have described the structure of the proximal vas deferens (segments one and two). The two tubes of segment one descend from the testes and gradually merge into segment two. The epithelium of segment one has synthetic activity and appears to contribute to the sperm-supporting matrix by exocytotic release of granules through its apical surface. The epithelium of segment two is also highly synthetic and secretes the primary spermatophore layer and part of the intermediate layer that surround the sperm mass. The trifoil shape of the extruded spermatophore is established through a change in height of some of the cells lining the lumen in segment two. Connective tissue and circular bands of striated muscle surround the epithelium of both segments.