The spermatozoon of Slavina appendiculata (Annelida, Oligochaeta)

The spermatozoon of Slavina appendiculata, an oligochaete annelid belonging to Naididae family, was studied with the purpose to provide new elements f or further discussion about phylogenetic relationship and taxonomic positio n. The filiform spermatozoon of this species presents the typical oligochae te components, characterized by: a corkscrew nucleus, 5 or 6 mitochondria i n the usual radial arrangement, a complex acrosome with an acrosome tube an d acrosome rod, and the distal axonema showing the tetragon fibers configur ation. Sperm cells in other naidids are compared with S. appendiculata sper matozoon as well as with the probable morphological relationships with the tubificids.