UC San Diego

Many crustaceans are prodigious scavengers and predators whose feeding behavior may be sensitive to environmental change, such as ocean acidification (OA) and ocean warming (OW). In this study, I tested the hypothesis that the feeding behavior of the rock crab, Cancer anthonyi, is affected by OA and OW conditions. Adult crabs were exposed to the following treatments (N=12 per treatment) for 8 weeks: ambient pH/ambient temperature (8.1 pH, 12℃), reduced pH/ambient temperature (7.7 pH/12℃), ambient pH/increased temperature (8.1 pH/16℃), or reduced pH/increased temperature (7.7 pH/16℃). Crabs were given two similarly sized mollusk prey items (mussel, Mytilus californianus and snail, Littorina spp.) twice per week and their feeding activity was video recorded for 5 minutes. A total of 14 feeding trials were performed in which multiple aspects of feeding behavior were recorded and compared across treatments: decision making time, prey handling time, prey preference, appetite (total number of prey consumed), prey consumption strategy, and shell damage to prey. Our results revealed sex-specific responses, whereby females had a lower appetite in the reduced pH/increased temperature treatment while males had a lower appetite in the reduced pH/ambient temperature treatment. All other feeding behaviors were unaffected by treatment. Two months of constant exposure to near-term OA and OW conditions are sufficient to alter some aspects of feeding behavior in adult C. anthonyi, despite natural exposure to environmental variations in upwelling regions of Southern California. The distinct responses observed in male and female crabs suggest that sex-based physiological differences should be considered in crustacean ocean acidification research.