Effects of temporary food limitation on survival and development of brachyuran crab larvae

Abstract

As a consequence of the combined effects of prey patchiness and diel or tidal vertical migrations in the water column, decapod crustacean larvae may experience temporal or spatial variability in the availability of planktonic food. In a laboratory study, we evaluated effects of temporarily limited access to prey on the larvae of three species of brachyuran crabs, Chasmagnathus granulata, Cancer pagurus and Carcinus maenas. Stage-I zoeae were fed ad libitum for 4 or 6 h per day (20 or 25% treatments; 6 h tested in C. pagurus only), and rates of larval survival and development were compared with those observed in continuously fed control groups (24 h, 100%). In C. granulata, we also tested if intraspecific variability in initial biomass of freshly hatched larvae originating from different broods has an influence onearly larval tolerance offood limitation.Moreover,weexposedembryosandlarvae of this estuarine species to moderately decreased salinities to identify possible interactions of osmotic and nutritional stress. Finally, we evaluated in this species the effect of food limitation on survival from hatching through all larval instars to metamorphosis. In all three species, limited access to prey had only weak or insignificant negative effects on survival through the Zoea-I stage. The strength of the effects of temporary food limitation varied in C. granulata significantly among broods. However, no significant relationships were found between initial larval biomass (C content) and either survival or development duration. Strongly decreased survival to metamorphosis was found when food limitation continued throughout larval development. Thus, early brachyuran crab larvae are well adapted to transitory lack of planktonic food. The capability of the Zoea-I stage of C. granulata to withstand nutritional stress also under conditions of concomitant salinity stress allows them to exploit various brackish environments within estuarine gradients. However, continued exposure to limited access to planktonic prey may exceed the nutritional flexibility of C. granulata larvae.