The anatomy and histology of the reproductive system of Aplysia oculifera (Mollusca: Heterobranchia: Aplsiida) from the Red Sea coastal waters

Abstract

ABSTRACT Aplysia oculifera is an endemic sea hare that inhabits the Egyptian coast of the Red Sea. We describe the reproductive system of this species for the first time. It is composed of an ovotestis, small hermaphroditic duct, nidamental glandular complex, large hermaphroditic duct, gametolytic gland, external seminal groove and cephalic penis. The follicles within the ovotestis contain spermatogenic and oogenic cells. A pre-ampulla, ampulla, and post-ampulla constitute the different regions of the small hermaphroditic duct. The nidamental complex consists of albumen, mucus, and membrane glands all confluent with the fertilization chamber. The nidamental glands consist of glandular cells alternating with supporting cells. The glandular cells have different histochemical characters concerning the production of acid and neutral mucopolysaccharides. The large hermaphroditic duct is attached to a seminal receptacle. The duct has two components; red and white hemiducts the secretory epithelia of which are distinguished internally. An atrial gland is present near the visceral genital opening. The gametolytic gland has four types of columnar cells. A seminal groove arises from the genital opening and extends anteriorly to the apex of an ear-like flap penis. The results suggest that some differences in certain reproductive characters may be of phylogenetic importance.