Specificity of host recognition of individuals from different host races of symbiotic pea crabs (Decapoda : Pinnotheridae)

Abstract

Host recognition must be important in the life history of pinnotherids which enter a host for a lifelong source of nourishment and shelter and as the principal site for mating. Host recognition may have a genetic basis and be an integral part of the behavioural repertoire, or may be influenced by experience and be a learned phenomenon. The occurrence and specificity of host recognition behaviour of adult Pinnotheres atrinicola Page and two populations of Pinnotheres novaezelandiae Filhol towards natural and novel hosts was examined. P. atrinicola, from horse mussels Atrina zelandica Gray, and P. novaezelandiae, extracted from the green-lip mussel Pema canaliculus Gmelin, were only attracted towards their natural host exudate. Crabs, nominally P. novaezelandiae extracted from the blue mussel Mytilus edulis aoteanus Powell, were highly attracted towards their natural host but showed a significant response towards high concentrations of P. canaliculus exudate. Attempts to induce an alteration in host recognition, by placing crabs in the mantle cavity of a novel host for a period of 4 wk, were unsuccessful, with crabs retaining highest sensitivity towards natural host exudates. No evidence for increased sensitivity towards the novel host was obtained. The specificity of response and its resistance to inductive change is interpreted to indicate that the populations under study represent biologically discrete units with different host recognition systems. The results suggest that the two populations of P. novaezelandiae from green-lip mussels and blue mussels are different host races, a conclusion supported by the degree of genetic differentiation between those host races noted in previous studies.