Spermatogenesis of the freshwater clam Corbicula aff. fluminea Muller (Bivalvia: Corbiculidae)

Spermatogenesis of the hermaphrodite freshwater clam, Corbicula aff. fluminea Muller was described from light and electron microscopy. During the spermatogenetic process, difference between primary and secondary spermatocytes was hardly recognized. Mature spermatozoon consists of an elongated head (13.9 +/- 0.32 mu m in length) with a rod-like acrosome, indistinct midpiece, and two long flagella, 2.5 times as long as the head, each flagellum with a very thin undulating membrane. Comparison of the sperm morphology in Corbicula species presents two major groups, uniflagellated and biflagellated. Spermatozoa of C. leana and C. aff. fluminea, in spite of their close similarity, were distinguished by their size and number of mitochondria.