SPERM ULTRASTRUCTURE IN NEMATOGENIA-PANAMENSIS (ANNELIDA, OLIGOCHAETA, OCNERODRILIDAE) - A PHYLOGENETIC APPROACH

Mature spermatozoa of Nematogenia panamensis (Annelida: Oligochaeta, O cnerodrilidae) from Madagascar were studied by electron microscopy. Th e spermatozoon is 35 mum long and shows the conventional clitellate se quence of acrosome, nucleus, middle piece and tail. The acrosome is as ymmetric, showing an acrosome rod consistently bent to one side and pr obably exiting laterally for a short distance from the acrosome vesicl e, only to re-enter apically. The middle piece consists of six mitocho ndria with the shape of a cylindrical sector and the tail is a flagell um with a 9+2 axoneme with two central tetragon fibers, surrounded for most of its length by glycogen granules. While the general features o f Nematogenia spermatozoon are undoubtedly of megadrile type, some cha racters, like the shortness of the acrosome and the basal chamber, ind icate a plesiomorphic condition within the group. This is in good agre ement with the proposed phylogenetic position of Ocnerodrilidae within the Oligochaeta.