STRUCTURE OF THE FEMALE REPRODUCTIVE-TRACT IN THE DUNGENESS CRAB (CANCER-MAGISTER) AND IMPLICATIONS FOR THE MATING SYSTEM

Anatomical and behavioral aspects of reproduction in female Dungeness crab, Cancer magister, were investigated. Female crabs were collected over a two-year period and external indicators of reproductive conditi on were recorded. A subset of crabs was retained for macroscopic and h istological examination of the reproductive tract. In addition, males and females were held in the laboratory for mating observations, thus providing females of known mating history for dissection. The spermath eca is of the ''ventral type,'' i.e., the vagina and the oviduct open into the spermatheca in close proximity to each other. A novel organ t hat often contains sperm, the bursa, is separate and distinct from the sperma theca in both position and origin and is reported for the firs t time for a brachyuran crab. The bursa is located just inside the vul va, distal to the spermatheca, and opens into the vagina. The sperm pl ug of C. magister; described here for the first time, is unique in for m among cancrids. The sperm plug is placed in the vagina by the first male to mate with a soft-shelled female and prevents subsequent access to the spermatheca. However, the sperm plug does not occlude the vulv a nor prevent subsequent copulation; ejaculates from subsequent mating s are deposited in the bursa. Hypotheses of the possible function of t he bursa are discussed.