FINE-STRUCTURE OF SPERMATOGENESIS IN MONOPISTHOCOTYLEAN MONOGENEANS (MACROGYRODACTYLUS-POLYPTERI - PSEUDODACTYLOGYRUS-BINI)

The development of spermatozoa in the monopisthocotylean fish gill flu kes, Macrogyrodactylus polypteri Malmberg and Pseudodactylogyrus bini Kikuchi was investigated by means of light and transmission electron m icroscopy. In M. polypteri spermatogonia give rise by successive mitos es to primary spermatocytes clearly characterized by the presence of s ynaptonemal complexes. In M. polypteri, spermatocytes are characterize d by a fine, dense intranuclear inclusion connected by a small strand to the nuclear membrane, and by the appearance of several Golgi comple xes. Both in M. polypteri and P. bini a syncytial mass of spermatids d evelops, which gives rise to 32 filiform spermatozoa. Mature spermatoz oa of M. polypteri have two axonemes, whereas P. bini has only one. In contrast to P. bini, spermatozoa of M. polypteri have a region with a lateral protrusion, formed by a fold of the spermatozoan membrane. Th e outer edge of the protrusion surrounds the mitochondrion. The observ ation that in M. polypteri, as well as in P. bini, the immature sperma tozoa are each situated within ring-shaped cytoplasmic canals in the s yncytial spermatids is comparable to findings in other monopisthocotyl ean species.