Larval mud crabs Rhithropanopeus harrisil were exposed continuously from hatching through the first crab stage to sublethal concentrations of naphthalene (0, 75, 150 or 300 kg I-') at several combinations of salinity and temperature (5, 15, or 25 ' ?>C. S and 20°, 25" or 30 "C, respectively), the experimentdl design consisting of a complete 3 X 3 X 4 factorial. Respiration rates were determined under all treatment comb~nations for the second and fourth zoeal stage, megalops and f~r s t crab. In

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... addition to a steady-state respiratory response at the rearing salinity, an osmotic-shock respiratory response was also assessed by ~respirometry immediately after transfer of larvae reared at 15 S to either 5 960 S (hypoosmotic shock) or 25 Zo S (hyperosmotic shock). Respiratory rates increased with temperature for all stages. Increases in the respiration rate of larval stages, especially zoeal stages, also occurred in low salinities. The increase due to low environmental salinity was least in the juvenile crab, probably because of development of the osmoregulatory capacity of the gill. Respiratory response to hypoosmotic shock was similar to that observed for steady-state trials at 5 %O S, but the pattern for hyperosmotic shock was intermediate between the steady-state response at 15 and 25 S* S. Naphthalene exposure usually resulted in a n increase i n respiration rate (of the zoeal stages) in low salinities. However, when physical conditions were not stressful, naphthalene effects generally were not obvious. The weight of megalops from the various trials (environmental factor combinations) was determined as an ind~cation of growth during zoeal develoment Growth was affected substantially by higher temperatures and lower salin~ties, and slightly by lower salinity-higher naphthalene combinatlons. At optimal salinity, 15 ?M S, no consistent effect of naphthalene on growth was apparent. This partial energy budget approach I S seen as a useful method for assessing long-term sublethal stress in marine invertebrates. growth of selected larval stages of the mud crab, Rhi-" Battelle New England Laboratories, 397 Washington t h r o~a n o~e u s hanisii, exposed throughout larval Street