Effect of temperature on red snow crab Chionoecetes japonicus (Crustacea, Decapoda, Majoidea) larval survival, development, and growth under laboratory conditions

In the Sea of Japan, the mature red snow crab Chionoecetes japonicus is distributed at a depth of 500-2,700 m. However, its planktonic larvae occur at depths shallower than 300 m. To better understand the factors influencing larval dispersal and settlement of the red snow crab in its natural habitat, we tested the effects of temperatures ranging from 1 degrees C to 18 degrees C on the survival, developmental period, and growth of red snow crab zoeal and megalopal larvae. The mean number of days from hatching to second zoeae and megalopae and from megalopae to the first crab instar was significantly shorter at warmer temperatures. Moreover, the relationships between mean temperatures and larval periods were well described by heat summation theory equations and a nonlinear thermodynamic Sharpe-Schoolfield-Ikemoto (SSI) model. The higher survival rate, intrinsic optimum temperatures in the SSI model, and larger carapace width suggested that the optimum temperatures for the development of zoeal and megalopal stages of the red snow crab are 9-10 degrees C and 7-8 degrees C, respectively. A lower optimum temperature in the megalopal stage than in the zoeal stages was considered an adaptation to facilitate deeper vertical distributions in the megalopal stage.