Somatic tissue-male germ cell barrier inHydra viridis (hydrozoa, coelenterata)

An ultrastructural study of testes permeability in sea urchins, Strongylocentrotus intermedius

Permeability of testes in sea urchins, Strongylocentrotus intermedius, was investigated by using an electron-opaque tracer, lanthanum nitrate. This tracer is able to enter the basal compartment of germinative epithelium, where developing germ cells are located. However, its ability to penetrate the gonadal lumen was reduced. An incomplete permeability barrier between the basal compartment and the gonadal lumen is supposed to exist in testes of S. intermedius.

Morphology of the male system and spermatophores of the arrowworm Ferosagitta hispida (Chaetognatha)

Transmission electron microscopy reveals that the somatic testicular tissues and sperm ducts are elaborations of the epithelial lining of the tail coelom. The testes consist of closely packed spermatogonia embedded between specialized lateral field cells. These cells contain few organelles and appear to function mainly as a compartment boundary. Masses of spermatogenic cells are released into the tail coelom from the anterior end of the testes. The sperm ducts, lined by simple cuboidal ciliated epithelium, collect mature spermatozoa from the tail coelom and convey them to the blindly ending seminal vesicles. The sperm ducts also modify coelomic fluid entering them along with the spermatozoa. The seminal vesicles consist of a simple glandular lining epithelium embedded in the stratified epidermis. Secretions of the lining epithelium surround the enclosed sperm mass and correspond in position to a noncellular spermatophore coat visible by light microscopy around released sperm masses. Spermatophores leave the seminal vesicles through a temporary split that forms between microfilament-containing suture cells. Maturation of spermatozoa and filling of the seminal vesicles is cyclical, occurring late each day. © 1994 Wiley-Liss, Inc.