Morphology of Paguristes eremita spermatophores and spermatozoa in comparison to those of other Mediterranean Diogenidae(Decapoda, Anomura) and their bearing on a sperm phylogeny of the family

The male reproductive apparatus of Paguristes eremita is described and compared with the description given for three other Mediterranean diogenids (Calcinus tubularis, Clibanarius erythropus, and Diogenes pugilator) already published. Paguristes eremita testes merge into a tubular duct made up of four zones: 1) the collecting tubule with free sperm; 2) the proximal zone, where the ampulla of the spermatophore starts to be formed; 3) the medial zone, where the ampulla is completed, the stalk lengthens and the pedestal is formed; 4) the distal zone, where the mature spermatophores are stored. In the mature spermatophore the two halves of the ampulla meet at the distinct lateral ridge. The spermatozoal ultrastructure was analysed and compared with that reported for the other species. Paguristes eremita spermatozoa have an almost conical acrosomal vesicle, they are capped anteriorly by a conical operculum and covered posteriorly by a cytoplasmic region comprising the nucleus and three microtubular arms. The acrosomal vesicle is posteriorly penetrated by the perforatorial chamber and is made up of different concentric zones. The available spermatozoal and spermatophore data is used to place P. eremita within a sperm phylogeny of the hermit crab family Diogenidae.