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

As a consequence of the combined effects of prey patchinessand diel or tidal vertical migrations in the water column, decapodcrustacean larvae may experience temporal or spatial variabilityin the availability of planktonic food. In a laboratory study,we evaluated effects of temporarily limited access to prey onthe larvae of three species of brachyuran crabs, Chasmagnathusgranulata, Cancer pagurus and Carcinus maenas. Stage-I zoeaewere 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 survivaland development were compared with those observed in continuouslyfed control groups (24 h, 100%). In C. granulata, we also testedif intraspecific variability in initial biomass of freshly hatchedlarvae originating from different broods has an influence onearly larval tolerance of food limitation. Moreover, we exposedembryos and larvae of this estuarine species to moderately decreasedsalinities to identify possible interactions of osmotic andnutritional stress. Finally, we evaluated in this species theeffect of food limitation on survival from hatching throughall larval instars to metamorphosis. In all three species, limitedaccess to prey had only weak or insignificant negative effectson survival through the Zoea-I stage. The strength of the effectsof temporary food limitation varied in C. granulata significantlyamong broods. However, no significant relationships were foundbetween initial larval biomass (C content) and either survivalor development duration. Strongly decreased survival to metamorphosiswas found when food limitation continued throughout larval development.Thus, early brachyuran crab larvae are well adapted to transitorylack of planktonic food. The capability of the Zoea-I stageof C. granulata to withstand nutritional stress also under conditionsof concomitant salinity stress allows them to exploit variousbrackish environments within estuarine gradients. However, continuedexposure to limited access to planktonic prey may exceed thenutritional flexibility of C. granulata larvae.