Reproductive products in the adult snow crab (Chionoecetes opilio). II. Multiple types of sperm cells and of spermatophores in the spermathecae of mated females

Abstract

Contents of the spermathecae of mated adult snow crabs (Chionoecetes opilio) were examined by light microscopy. The contents could consist of water and three basic types of amorphous matter and of spermatophores. Water was present in the form of large patches or smaller spheres. Of the two major types of amorphous matter, one reacted positively and one negatively to periodic acid - Schiff's reagent (PAS), and one was only, and one predominantly, of male origin. The minor type of amorphous matter was orange and of female origin and could include dark cellular debris. Spermatophores enclosed either immature spermatids, mature spermatids, hitherto unreported spermatozoa, or cell forms intermediate between these three types. Peripheral mature spermatids and spermatozoa had a polarized orientation and were attached to the spermatophore wall. Overall, amorphous matter and spermatophores were topographically segregated by type within a spermatheca, and spermatophores enclosing immature spermatids occurred mostly in PAS-negative amorphous matter. Spermatid differentiation can unfold in the female reproductive tract as well as in the vas deferens, while the transformation of spermatids into spermatozoa was observed only in the female. The diversity of sperm cell types and the ordered placement of semen constituents within the spermatheca suggest that sperm are partitioned for short- or long-term use.