Ultrastructure of the Spermatophore Lateral Ridge in Hermit Crabs (Decapoda, Anomura, Paguroidea)

The pedunculate spermatophore is characteristic of the Anomura, and the Paguroidea in particular. It has a sperm-filled ampulla which is composed of two valves joined at a conspicuous lateral ridge. This lateral ridge is a thickening of the spermatophore wall but also a discontinuity between the wall morphology of each valve. Within the hermit crabs (Paguroidea) the spermatophore wall morphology can be divided into three categories: fibrillar, heterogeneously granular and homogeneously granular. The fibrillar form is found in representatives from the families Coenobitidae and Diogenidae, with the exception of those of the genus Clibanarius which have the heterogeneously granular form, while the homogeneously granular form has been recorded from members of the family Paguridae. A single galatheid crab, Allogalathea elegans is shown to have a homogeneously granular spermatophore wall and ridge like this latter group of paguroids. These differences in spermatophore wall and ridge morphology between the various taxa in the Anomura appear to be phylogenetically significant.