Handling methods used by the velvet swimming crab Liocarcinus puber when feeding on molluscs and shore crabs

Abstract

ABSTRACT: Velvet swimming crabs Liocarnnus puber, collected in Gwynedd, N. Wales, were observed feeding in the laboratory on winkles Littorina rudis, mussels Mytilus edulis, and juvenile shore crabs Carcinus maenas. Handling methods were recorded, and for mussels and shore crabs only. handling times were measured. Since C. maenas is mobile and can escape from some attacks, attack success rate was quantified for this prey. Specific methods for opening larger molluscs were apparently determined by geometry and strength of shell, which limited the positions in which the chela could exert sufficient force without slipping. No specialized opening techniques existed for small molluscs, which were crushed outright, and for shore crabs, which were torn apart without difficulty. Total handling time for both prey types was described by the equation y = ax + b, where y = log(time); X = prey length or carapace width/log(predator carapace width). Handling time of M. edulisconsisted of 3 components. Breaking and eating times of large mussels were positively correlated with prey size; breaking time of small mussels, which could be crushed with a single application of force, was independent of prey size. Picking-up time was short, and negatively correlated with prey size. indicating that L. puber, due to lack of chelal dexterity, had difficulty picking up smaller prey. Similarly, attack success rate on C. maenas increased with prey size The 2 CO-existing portunid crabs L. puber and C. maenas show many similarities in their prey handling behaviour. However, chelal morphologies suggest that C. maenas is adapted to feeding on molluscs while L. puber is better equipped for predation on softer, more mobile prey such as crustaceans