Manipulation of Cerastoderma edule burrowing ability by Meiogymnophallus minutus metacercariae?

Metacercariae of various digenean trematodes are assumed to impair the burrowing capacity of cockles Cerastoderma edule. To reveal if metacercarial infections of the gymnophallid Meiogymnophallus minutus have effects on burrowing and shell closure, a laboratory experiment using cockles with slight and extremely heavy infections was performed at water temperatures of 15, 20, and 25C. Gaping of the cockle shell valves or other behavioural abnormalities, which have previously been ascribed to M. minutus infections, were not observed. Neither response time nor burrowing time differed significantly between slightly and heavily infected cockles at any of the temperatures tested, suggesting that the effects of the digenean trematode on its second intermediate host are not necessarily as pronounced as proposed by earlier publications, not even when additional environmental stress in the form of high water temperatures is present. Our findings question the hypothesis that M. minutus manipulates the behaviour of C. edule, in order to increase the probability of successful transmission to the avian final host.