ULTRASTRUCTURE OF SPERM CELLS IN THE FEMALE GONODUCT OF FREE-LIVING MARINE NEMATODES FROM GENUS ENOPLUS (NEMATODA, ENOPLIDA)

The ultrastructure of mature spermatozoa in two marine enoplid nematod es Enoplus demani and Enoplus anisospiculus was studied with a transmi ssion electron microscope. Both species have very similar bipolar sper m. The sperm cells show an amoeboid motility and are subdivided into a nterior pseudopod and rigid cone-shaped posterior part filled with org anelles. The cytoplasm of the pseudopod contains only a fibre network of cytoskeleton. In E. anisopiculus pseudopod numerous tube-like vesic les were found. The nucleus is built up of a strongly condensed mass o f chromatin surrounded by the distinct nuclear envelope. Numerous mito chondria tend to concentrate at the base of the pseudopod before the n ucleus. Membranous organelles of two types were found in the mature sp erm of both species. Spherical organelles located more centrally are n ot connected with plasma membrane and contain an electron-dense materi al penetrated by internal microvilli. Electron-transparent membranous organelles are concentrated beneath the plasma membrane and open to th e exterior via pores. These organelles have a more elaborate system of internal microvilli.