Some aspects of the reproductive biology of the American lobster (Homarus americanus Milne-Edwards)

Some aspects of the reproductive biology in the American lobster Homarus americanus were investigated.;b. Structure of the seminal receptacle and its contents. The seminal receptacle, located between the last two pairs of walking legs of the female, is an interpocketing of the exoskeleton, which receives spermatozoa from the male. The spermatozoa are stored inside the spermatophore in the dorsal portion of the seminal receptacle and separated from the external aperture by the sperm plug. Histological and histochemical observations did not reveal any differences between sperm plugs of mature and berried females.;c. The role of the ;d. Fertilization mechanism. A female with the external aperture of its seminal receptacle completely sealed with dental cement, was able to fertilize eggs which developed normally. This contradicts previous assumptions that spermatozoa leave the seminal receptacle via the external aperture. A hollow, elongate structure was found beside the oviduct; this is suggested to be a transitory connection between the oviduct and the seminal receptacle.;a. Structure and activity of the oviduct. Light and electron microscopic observations revealed that the oviduct is formed of three components: a fibrous tunic, the epithelium and a basal lamina between the first two. The epithelium is formed by simple columnar cells with nuclei basally located. The basal regions of the cells are highly interdigitated. The apical surface carries blunt or thin cytoplasmic projections towards the lumen. The cytoplasm is populated with numerous mitochondria, Golgi bodies, agranular and granular endoplasmic reticulum, ribosomes, vacuoles, autolysosomes and residual bodies. However, evidence of pronounced synthetic activity of the oviduct was not obtained, a finding corroborated by histochemical tests (Periodic Acid/Schiff; Alcian Blue; Alcian Blue/PAS; Millon Reaction and Sudan Black B) performed on oviducts removed in different stages of the reproductive cycle.;The possibility of internal fertilization in the American lobster is discussed in the light of the results obtained.