HISTOLOGY OF THE REPRODUCTIVE SYSTEM OF THE SOFT-SHELL CLAM (MYA ARENARIA)

¹ Bureau of Commercial Fisheries Biological Laboratory, Boothbay Harbor, Maine

1. The reproductive organs of Mya arenaria consist of paired alveolar gonads, connected by paired gonoducts to a (usually) common vesicle. From the vesicle, a pair of short terminal gonoducts lead to the genital apertures.

2. The region occupied by the vesicle, terminal gonoducts and genital apertures is invested with muscular and connective tissue and is highly innervated with branchlets from the cerebro-visceral commissures which pass through the region. Paired branches from these nerve trunks also follow the main gonoducts into the gonad.

3. The terminal gonoducts are lined by longitudinally furrowed epithelium of ciliated columnar cells. In many individuals groups of these cells alternate with groups of non-ciliated, elongated cells with bulbous tips, apparently secretory in function.

4. Evidence is cited to show that sex products are accumulated in the genital vesicle prior to spawning. Homologous structures in two other species of lamellibranch are described which serve the same purpose.

5. An apparent relationship is shown between the time and site of egg activation and the nature of the epithelium of the terminal gonoduct of four species of lamellibranch molluscs.