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

摘要

The development of spermatozoa in the monopisthocotylean fish gill flukes, Macrogyrodactylus polypteri Malmberg and Pseudodactylogyrus bini Kikuchi was investigated by means of light and transmission electron microscopy. In M. polypteri spermatogonia give rise by successive mitoses to primary spermatocytes clearly characterized by the presence of synaptonemal complexes. In M. polypteri, spermatocytes are characterized by a fine, dense intranuclear inclusion connected by a small strand to the nuclear membrane, and by the appearance of several Golgi complexes. Both in M. polypteri and P. bini a syncytial mass of spermatids develops, which gives rise to 32 filiform spermatozoa. Mature spermatozoa 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. The outer edge of the protrusion surrounds the mitochondrion. The observation that in M. polypteri, as well as in P. bini, the immature spermatozoa are each situated within ring-shaped cytoplasmic canals in the syncytial spermatids is comparable to findings in other monopisthocotylean species.