ULTRASTRUCTURAL AND CYTOCHEMICAL OBSERVATIONS ON THE SPOROGENESIS OF SPHAEROSPORA-TESTICULARIS (PROTOZOA, MYXOSPOREA) FROM MEDITERRANEAN-SEA BASS, DICENTRARCHUS-LABRAX (L)

The ultrastructure and cytochemical features of Sphaerospora testicula ris found in the testes of cultured sea bass (Dicentrarchus labrax) ar e described. A hypothesis for the developmental cycle of this myxospor ean in the lumen of seminiferous tubules is suggested. The initial sta ge, a primary cell (P), generates by endogenous division a secondary c ell (S) which divides mitotically producing two S cells. The latter di vide again by endogeny generating tertiary cells (T) within them. Afte r mitotic division, T cells can be considered sporogonic, as they unde rgo meiosis and further differentiation giving rise to mature spores. Differences of this cycle to that of other sphaerospores are discussed . The S. testicularis stages show the typical features of myxosporean organization. Cytochemically, low levels of polysaccharides were detec ted in most stages, but lipidic vacuoles were relatively abundant. Des mosome-like junctions occur between capsulogenic cells, and there is a filamentous plug attachment of the polar capsule.