AN ULTRASTRUCTURAL OVERVIEW OF TUBIFICID SPERMATOZOA

The spermatozoa of seven species of tubificid oligochaete were compare d to those already described in order to supply spermatozoal character s for systematic work on Tubificidae. The spermatozoa of Clitellio are narius (subfamily Tubificinae) resemble those of the two other known m embers of the subfamily (Tubifex tubifex and Tubificoides amplivasatus ) in being of two different types and in showing the same morphology o f acrosomes and nuclei. Among Phallodrilinae, the three gutless specie s Inanidrilus bulbosus, Inanidrilus leukodermatus and Olavius planus s hare with Bathydrilus formosus the shape of the nucleus and various ch aracters of the acrosome, whereas Thalassodrilus prostatus is particul ar in having the acrosome vesicle external to the tube and the longest middle piece recorded in oligochaetes. Monopylephorus limosus and Rhi zodrilus russus (Rhyacodrilinae) differ widely in acrosomal and nuclea r characters: M. limosus has a twisted nucleus, whereas R. russus has an apically flanged nucleus with a conspicuous apical concavity and an endonuclear canal. The data published on spermatozoa of the Limnodril oidinae are reviewed.