Behavioural responses of the supralittoral amphipod Talitrus saltator (Montagu) to trace metals contamination

We investigated behavioural responses (locomotor activity and substrate selection) of the amphipod Talitrus saltator after laboratory exposure to different concentrations of Hg, Cu and Cd. Locomotor activity, measured with a microwave radar device, was assessed in animals exposed to contaminated sand and in sandhoppers previously kept for 48 h in contaminated seawater and tested in clean sand. The contents of Hg, Cu and Cd in T. saltator tissues were measured at the end of pre-exposure to contaminated seawater and after 7 days of exposure to contaminated sand. Substrate selection tests were carried out in a binary choice arena. Tests in contaminated sand showed that sandhopper locomotor activity varied in a dose-dependent manner in the presence of Cu and Hg (at lower Hg concentration they were more active during daytime) but did not show significant changes in Cd-exposed animals except for disappearance of the typical circadian activity pattern. Pre-exposure to trace metals in seawater induced a significant decrease of movements for all metals, although the effects varied according to the toxicity of the metal. Trace metals analyses showed that tissue concentrations of Hg, Cu and Cd were related to their concentrations in the test medium. Substrate selection tests showed avoidance of contaminated sand only when sandhoppers were tested in the presence of both concentrations of Hg and at the higher concentration of Cu. In conclusion, locomotor activity and avoidance behaviour of T. saltator could be used as behavioural biomarkers of trace metals exposure.