Chemosensory behaviour in the mud crab, Rhithropanopeus harrisii tridentatus from martwa wisla estuary (Gdansk Bay, Baltic Sea)

Abstract

Experiments were carried out to study the effects of food signal concentration, animal nutritional status, and signal repetition on behavioural responses of the mud crab, Rhithropanopeus harrisii tridentatus. Starved crabs responded to a food stimulus by maxilliped movements, chela probing, cleaning movements by the first pair of walking legs, and locomotion. A low concentration of the stimulus elicited only detection, medium concentrations triggered far-field food search, and high concentration activated near-field food search. These results indicate that crabs use the stimulus concentration as a source of information about their distance from a food item. Fed animals reacted to a full-strength food stimulus by escaping from the place where such odour was released. No search behaviour was elicited. Such strategy can decrease the risk of encountering predators or cannibalistic conspecifics by animals that are not under the imminent danger of starving. Stimulus repetition had an inhibitory effect on crab behavioural reactions. The degree of blockade was decreasing with the increase in time between successive stimulus applications. These results indicate that crabs may have a learning mechanism, protecting them from repeating useless food search.