Specimens of the spider crabs Hyas coarctatus and Inachus dorsettensis were reared in the laboratory under ambient temperature conditions. Individuals were retained until they had undergone two moults, or moulted. to the terminal instar: they were then replaced by fresh specimens. The percentage increment was recorded for each moult, and the duration for each intermoult period. Both intermoult period and percentage increment either declined with increasing temperature or showed no response. The effect of body size on these variables tended to reflect that expected in species with determinate growth-intermoult period generally increased with size, whereas percentage increment remained unchanged. Percentage increment was compared between juvenile moults and the puberty moult in both this and earlier studies. In males, the puberty moult increment was smaller than juvenile increments, and this is tentatively related to the diversion of resources to the large puberty increase in chelar size. In females, the puberty moult increment was either larger or smaller, dependant on whether the ovaries matured after or before the puberty moult, respectively-again a reflection of resource allocation. Growth curves constructed from the laboratory data were compared with those based on field studies. These analyses emphasised that seasonal constraints in natural populations could compromise predictions from laboratory experiments. (C) 2001 Published by Elsevier Science B.V.
