Mating and the inferred function of the genital system of the nudibranch, Aeolidiella glauca (Gastropoda : Opisthobranchia : Aeolidioidea)

We describe the genital system of the aeolid nudibranch gastropod Aeolidiel la glauca as a basis for our ongoing analysis of the mating system of this hermaphroditic species. In addition we give a short account of its mating b ehavior. A. glauca has an androdiaulic genital system with a proximally sit uated semiserial seminal receptacle. There is no bursa copulatrix. After fe rtilization, eggs pass through six glands, i.e., the capsule gland and the female gland mass which is comprised of five histologically differentiated parts. The prostate is a long, glandular tube. The everted, unarmed penis i s very large and bears a series of 3-4 hook-shaped lobes consisting only of a simple, ciliated epithelium on its ventral side. Their function is unkno wn. After courtship, which involves moving in circles followed by resting i n a head-to-head position, reciprocally touching each other with the tentac les, the slugs glide into a position where the everted genital atria are in contact. The huge penes are protruded simultaneously shortly after this co ntact occurs. Each animal strokes its partner's back with the penis and dep osits a spermatophore of undetermined shape onto the partner's notum. Sperm enter the recipient through histolysis. How the sperm find their way to th e seminal receptacle is not known.