Effects of short - term food variability on the plasticity of age and size at metamorphosis of porcelain crab larvae

In a series of three experiments, we tested the effects of short-term food variability on the larval development of Petrolisthes cabrilloi. We first reared seven sibling clutches of zoeae at 19°C in ten constant food rations (ranging 2-40 Artemia nauplii d) to determine maximal and minimal values for age and size at metamorphosis to the megalops stage. Mean age at metamorphosis ranged between 18.3-38.0 d after hatching and correlated negatively with food. Mean dry mass of megalopae ranged between 71.8-296.0 μg and correlated positively with food. The effect of food ration overwhelmed the small variation among clutches. Data from this experiment involving non-varying food rations were applied to a model of metamorphosis in variable environments to make quantitative predictions for more complicated regimes in which food varies during development. We tested the predictions by performing two experiments in which larvae were switched between high-food and low-food rations at various developmental stages and at controlled times. Size at metamorphosis was plastic throughout the entire larval period, but plasticity in the timing of metamorphosis was lost during the final 20-30% of the larval period. More importantly, data from the variable feeding regimes were within 95% confidence intervals for 14 of the 16 model predictions for age and size at metamorphosis. The model allowed the results of relatively simple experiments involving several non-varying food rations to be extrapolated to more complicated scenarios involving short-term food variability.