CHARACTERISTICS OF THE SPERM FLAGELLUM IN FUNGUS GNATS (INSECTA, DIPTERA, MYCETOPHILOIDEA)

Spermatozoa from several members of the closely related Mycetophilidae and Keroplatidae were examined by electron microscopy using a fixativ e that contains glutaraldehyde and tannic acid, followed by a post-fix ative that consists of uranyl acetate rather than osmium tetroxide. Wi th this fixative, the detailed architecture of the flagellar axoneme a nd its various microtubules could be resolved. The so-called accessory tubules, which surround the central 9 + 2 unit of the sperm axoneme, were found to have 16 protofilaments in several examined Mycetophiloid ea, but in no other Diptera. As 16 is the common number in holometabol ic insects, it is presumably the plesiomorphic condition in Diptera. O ther fungus gnats have accessory tubules with 15 or 14 protofilaments. The intertubular material situated between the accessory tubules is s maller in the examined members of the Mycetophilidae than in the Kerop latidae. The acrosome consists of an apical vesicle, which in one spec ies, Macrorhyncha ancae, has three microtubular doublets in its anteri or part and two large and three small extensions which extend posterio rly along the sperm axoneme.