The neck region of the spermatozoon of discus rotundatus (muller) (pulmonata, stylommatophora)

The neck region of the mature spermatozoon of discus rotundatus is described. No evidence for a centriole or centriolar derivative is obtained. Nine striated coarse fibres and the two central fibres of the axoneme extend into the base of the implantation fossa. The axonemal doublet system is disrupted in the neck region. There are two fibrous acessory structures located between the central doublet and the striated coarse fibres (AU)