Sperm flagellum of Insects belonging to orders Psocoptera, Mallophaga and Anoplura - ultrastructural and phylogenetic Aspects

Spermatozoa from seven insect species belonging to the three orders Psocoptera, Mallophaga and Anoplura were examined by electron microscopy. Primary fixation was in a glutaraldehyde- tannic acid mixture and post-fixation in 1% uranyl acetate rather than in an osmium tetroxide solution. With this fixation method the individual protofilaments of the axonemal microtubules are well resoved. The accessory tubules of the axoneme were found to have a wall consisting of 13 rather than 16 protofilaments, to have an elliptic cross-section, and to have a lumen that appears electron-dense except for a less dense central axis. The centriole was seen to consist of nine microtubular doublets, rather than triplets, and nine accessory tubules located at some distance from the doublets. The centriolar doubles are immersed in an electron-dense material termed centriolar adjunct. These listed features of accessory tubules seem to be synapomorphic traits; they have not been seen in any other insect species. All examined species belonging to Mallophaga and Anoplura and most species of Psocoptera have spermatozoa with two axonemes. Phylogenetic conclusions drawn from sperm ultrastructure are in perfect agreement with previous data based on somatic features.