William E. Donaldson

ETHOGRAM OF BEHAVIOR WITH EMPHASIS ON MATING FOR THE TANNER CRAB CHIONOECETES BAIRDI RATHBUN

Laboratory observations of mating behavior of the Tanner crab Chionoecetes bairdi are described and compared with similar phenomena in other brachyuran crabs. Twenty-seven distinct actions were performed by C. bairdi during 133 matings. Seven actions-carapace caressing, bouncing, body lifting, palpating, sternum-to-sternum positioning, intromission, and pull-up-were unique to reproduction. Grasping, antennule flicking, sternum-to-sternum positioning, vigorous moving of mouthparts, and intromission were common to every complete copulation. Most primiparous females mated shortly after their maturity molt while in a new, soft-shelled condition. However, other primiparous females mated in a semihard-shelled condition as late as 21 days after the maturity molt and still produced viable zygotes. Multiparous females were able to fertilize eggs with sperm stored in their spermathecae during the preceding breeding season. Breeding recurred when males were present at the time multiparous females were receptive (during and shortly after the hatching of their eggs). Courtship, which is subtly developed, entails precopulatory attendance of the female by the male and performance of actions (body lifting, beating, and kicking) which quiet the female if she attempts to escape. Ungentle male-female interactions were infrequent when the females exoskeletal condition was new and soft, more frequent when the female had a new semirigid exoskeleton, and prevalent when the female had an old, hard exoskeleton. In consequence, both the ability of the females to thwart breeding attempts by small and/or weak males and the occurrence of grasping marks on female exoskeletons directly increased with exoskeletal hardness. In some instances more than one male copulated with individual females. The brachyuran crab Chionoecetes bairdi Rathbun is widely distributed in the northern North Pacific Ocean between the central

Epibionts of the Tanner Crab Chionoecetes Bairdi in the Region of Kodiak Island, Alaska

ABSTRACT We examined the epibionts on 98 legal male Tanner crabs (Chionoecetes bairdi) of varying, known shell ages, which were tagged in the region of Kodiak Island, Alaska, and recovered in the commercial fishery. We found 39 species or collective taxa of organisms on C. bairdi, a conservative estimate of the number of species involved. Seven species or collective taxa occurred on the exposed outer surface of ≥50% of all crabs examined: Alcyonidium sp., Balanus spp., a tube-dwelling amphipod, Spirorbis spp., Serpula spp., a lichenoporid bryozoan, and the fungus Trichomaris invadens.At least 12 species occurred in the branchial chamber. Of these, Triticella sp., Alcyonidiumsp., and mucoid-tube polychaetes were found in ≥50% of 25 branchial cavities examined. Three species (Triticella sp.; a small, white flatworm; and Hiatella arctica) were found only in the branchial chamber. Our data showed trends of increasing frequency of occurrence and increasing mean number of epibionts with increasing shell age. Crab-shell age was a significant factor in determining the number of epibiotic species on crabs; the area of origin was not a significant factor. Epibionts are likely to be of limited use as a management tool, because of difficulties in accurately assessing the age composition of commercial samples and the likelihood of temporal and geographic variation in recruitment of epibiont organisms. However, epibionts are probably a significant factor in the population dynamics of C. bairdi and, hence, worthy of further investigation.

Shell Condition and Breeding Success in Tanner Crabs

ABSTRACT When pairs of similar-sized old-shell and new-shell male Chionoecetes bairdi Rathbun were presented with multiparous mates, the old-shell males dominated during 70% of the copulations. In 39% of all copulations, possession of the female was contested. Old-shell males won 69% of those contested matings. Males that recently molted did not copulate with either primiparous or multiparous females.

FIRST OBSERVATIONS OF PODDING BEHAVIOR FOR THE PACIFIC LYRE CRAB HYAS LYRATUS (DECAPODA: MAJIDAE)

ABSTRACT This paper reports the first observations of podding behavior (aggregation) for the Pacific lyre crab Hyas lyratus near Kodiak Island, Alaska. Pods containing approximately 2,000 crabs of both sexes were observed on 2 separate occasions during dives in the 2-person submersible Delta in April 1991. The pods appeared to be mating aggregations. The pods occurred in an average depth of 115 m.