INFLUENCE OF TEMPERATURE ON LARVAL DEVELOPMENT OF 4 COOCCURRING SPECIES O THE BRACHYURAN GENUS CANCER

Effects of temperature on zoeal development of Cancer productus, C. or egonensis, and C. gracilis collected from Puget Sound, Washington, USA , were determined and compared with published data on C. magister. Sur vival through zoeal development, mortality per individual zoeal instar , instar duration, and megalopa weight were determined for zoeae of ea ch species raised in the laboratory at 10, 15, and 20-degrees-C. In co nstrast to larvae of C. magister, the larvae of both C. productus and C. gracilis survived to the megalopa at 20-degrees-C. Larvae of C. ore gonensis, however, died by Zoeal Stage 3 at 20-degrees-C. Individual i nstar mortality rates varied as a function of temperature among specie s, reflecting different patterns of thermal tolerance through ontogeny . Zoeal duration varied inversely with temperature, although differenc es between 10 and 15-degrees-C were far greater than those between 15 and 20-degrees-C in each species. Duration of individual zoeal instars varied as a function of temperature and species. Megalopa weight was significantly reduced at 20-degrees-C in C. productus and C. gracilis, although no differences were measured between 10 and 15-degrees-C in any of the four species. Although literature reports indicate that rep roductive output varies directly with adult size in these Cancer speci es, the larval traits measured here varied independent of body size.