Larvae of the rock crab Cancer irroratus were found to b e eurythermal and stenohaline during development. Complete development occurred between 1 0 " and 24 "C in 30 960 S. Survival to the megalopa stage ranged from 20 % (at 10 'C) to 83 % (at 24 'C) Development was successful in 25, 30 and 35 %o S at 15 "C, but survival exceeded 50 % only in 30 and 35 460 S. Temperature and salinity significantly influenced molt frequency, intermolt duration and larval size. Maximum growth at metamorphosis was found at the mid-range of the thermal tolerance lini~ts (15O-18 'C). Comparison of these laboratory-determined data on survival and growth with available field data on the life history of C. irroratus suggests that the majority of larvae are released during that portion of the spawning period when larval wastage would be minimized and recruitment to the parental and regional populations would b e maximized.

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Balanced energy budgets were estimated for larval stages of the rock crab Cancer irroratus cultured in 6 combinations of temperature and salinity. The energy consumed by larvae during developn~ent increased in all culture conditions although consumption in 10 'C -30% S was significantly lower than for larvae in other conditions (15 "C -25 ' %o S, 15 "C -30 %O S, 15 "C -35 %o, 24 "C -30%0 S). Maintenance costs for the entire developmental period were highest for larvae cultured at 10°C -30% S and 15°C -25% S. Larvae under these conditions had net growth efficiencies of only 32-34 %. In the other temperature and salinity conditions tested, the amount of energy expended for maintenance was generally equal to the amount of energy converted to new tissue with net growth efficiencies varying between 4 8 and 51 %. These data suggest that the larva's ability to acquire energy resources and effectively partition the energy obtained between maintenance and growth depends on environmental factors. Under certain conditions (lO°C -30% S, 15OC -25 % S ) larvae are unable to compensate physiologically for environmental changes. One consequence of incomplete physiological compensation is a reduced potential for growth and an overall reduction in the organism's ecological fitness within the zooplankton community.