Effect of hypoxia on the prey-handling behaviour of Carcinus maenas feeding on Mytilus edulis

The shore crab (green) Carcinus maenas commonly occurs in tide pools and channels where temporary hypoxia is experienced. Under such conditions, aerobic metabolism is Limited, with possible consequences to prey-handling behaviour. We investigated this possibility by measuring the prey-handling times of C. maenas fed mussels Mytilus edulis under normoxic (5.9 +/- 0.1 mg O-2 1(-1)) and hypoxic conditions (1.08 +/- 0.12 mg O-2 I-1). The prey-handling time of smaller crabs (5.0 to 5.3 cm carapace width) feeding on relatively small, medium and large mussels was increased by hypoxia. The prey-handling time of larger crabs (7.1 to 7.3 cm carapace width) was increased by hypoxia only when feeding on relatively large mussels. Increases in prey-handling time were largely due to increases in the time taken to glean and ingest flesh, except for large mussels, for which time taken to break the shell became more important. The results show that hypoxia reduces prey-handling efficiency, presumably by limiting the capacity to increase aerobic metabolism, and that susceptibility to this decreases with increasing body size. Reduced prey-handling efficiency could place individuals at greater risk to competition and predation when subjected to hypoxia in the field.