A Bilateral Gynandromorph of the Snow Crab, Chionoecetes Opilio, From Newfoundland, Canada

Abstract

In July of 1982 an unusual specimen of the snow crab, Chionoecetes opilio (O. Fabricius, 1788), was caught by a commercial crab fisherman at a position ap proximately 40 km N.E. of St. John's, Newfoundland, at a depth of 185 m. The animal was of 102 mm carapace width, indicating that it was probably sexually mature (Watson, 1970, found that 50% maturity occurred at 57 and 50 mm for males and females, respectively). Its shell condition was classified as new, being hard with very little epibiotic growth, indicating that it had probably molted recently. Further external examination revealed that this animal is apparently a true bilateral gynandromorph. When viewed dorsally (fig. 1) the right side of the animal is typical of mature males while appendages on the left side are greatly reduced in size in proportion to the carapace width. Ventrally the body of the animal was differentiated bilaterally into a male and a female side. The right half exhibits a typical male abdomen which is broad at the base but tapers anteriorally to a slightly rounded tip. The left half exhibits the broad rounded configuration typical of a sexually mature female snow crab (fig. 2). Beneath the abdomen the secondary sexual characteristics are again typical and complete for each sex on their respective sides. On the male half, pleopods are modified so as to effect the transfer of spermatophores into the seminal receptacle while the female half of the animal consists of a seemingly complete seminal receptacle and biramous pleopods used for egg attachment (fig. 3). Although dissection of the animal in order to determine whether or not sper matophores were present in the vas deferens and whether there were mature ova in the ovary could have been informative, this was not attempted as the specimen had been cooked and frozen upon collection in a misguided attempt at preservation.