SPERMATOZOAN MORPHOLOGY OF 19 SPECIES OF PROSOBRANCH LIMPETS (PATELLOGASTROPODA) WITH A DISCUSSION OF PATELLID RELATIONSHIPS

The spermatozoon morphology of 19 species of Indo-Pacific, East Atlant ic and Mediterranean patellid limpets was examined by transmission ele ctron microscopy. All nine species of Patella and Helcion from the Sou th Atlantic (southern Africa) and the Indo-Pacific, as well as three s pecies from the North Atlantic, have sperm which correspond to one of the sperm groups I, II or III, previously described for patellacean li mpets from southern Africa (Hodgson & Bernard 1988). With the exceptio n of P. safiana and P. canescens, all 7 Patella species from the N.E. Atlantic/Mediterranean have sperm morphologies which closely resemble one another but are distinctly different from the sperm types of speci es in the southern hemisphere. These N.E. Atlantic/Mediterraean limpet s have been assigned to a new sperm group, group VI. On the basis of s perm structure it is suggested that patellid limpets had three main ce ntres of radiation: a N.E. Atlantic/Mediterranean centre; an East Atla ntic centre with its focal point on the S.W. coast of southern Africa; an Indo-Pacific centre with its focal point on the S.E. coast of Sout h Africa. Despite similarities between the species within groups, each has a unique sperm. An examination of spermatozoa of one patellid fro m Namibia and one from S. Angola (both initially identified as Patella miniata), has revealed that their sperm are distinctly different, as well being different from that of P. miniata from South Africa. Subseq uently, the species from Namibia was identified as P. adansonii. Furth ermore, P. cf. miniata from S. Angola had a sperm which is remarkably similar to that of P. safiana from N.W. Africa and the two may be cons pecific.