Spermatogenesis/Spermiogenesis and Spermatophore Packaging in the Testes and the Anterior/Medial Vas Deferens of the Newfoundland and Labrador Snow Crab (Chionoecetes opilio Fabricius, 1788)

The Newfoundland and Labrador snow crab (Chionoecetes opilio) fishery is one of the most valuable in North America. Recent observations, however, have indicated declines in reproductive fitness with links to sperm quantity or quality. Issues linked to sperm viability in brachyuran crabs may be traced to the initial stages of spermatogenesis/spermiogenesis in the testes, as well as during spermatophore packaging in the vas deferens. To explore these processes and determine a baseline for normality, a combination of histological and histochemical techniques was applied to investigate the early sperm development and spermatophore formation in the testes and vas deferens of wild Newfoundland C. opilio. The testes were composed of tubular lobules which were divided into three zones (developmental, multiplication, and ripe) based on the developmental stage of the resident germ cells. The developmental progression of the cells in each zone was defined by distinct changes in the shape and position of the nucleus and the formation of the acrosomal groove and the acrosome specifically. Spermatogonial stem cells and associated accessory cells were localized to the developmental zone. Spermatocytes and early spermatids were resident in the multiplication zone. The ripe zone contained small populations of mid- and late-stage spermatids. Developing cells in both the multiplication zone and the ripe zone stained intensely with Periodic Acid-Schiff's reagent (PAS), suggesting general carbohydrate but not glycogen storage. The anterior vas deferens (AVD) collected late-stage spermatids from the testicular ripe zones in preparation for organization and packaging into spermatophores. The AVD was lined by low columnar epithelial cells containing a basal nucleus. Associated epithelial secretions were slightly reactive with PAS and eosin during the spermatid organizational stage; however, subsequent seminal secretions in the distal AVD and the medial vas deferens containing individual packaged spermatophores stained intensely with PAS suggesting a changing role for these secretions during transport to the posterior region of the vas deferens. Updated morphological descriptions of C. opilio spermatocyte and spermatid development and spermatophore packaging in the present study provide new insights into the timing and spatial distribution of these processes in this species.