Behavioural adaptation to different salinities in Talitrus saltator (Crustacea: Amphipoda): Mediterranean vs. Baltic populations

The sandhopper Talitrus saltator is common on sandy beaches at different latitudes. Therefore, behavioural variations allowing them to cope with a wide range of environmental variation are expected. To test the hypothesis that behavioural adaptations to natural environments are characterised by different salinities, we compared two behaviours (substrate choice and escape from immersion) of two T. saltator populations from a Mediterranean (high salinity) and a Baltic Sea (low salinity) sandy beach. T. saltator preferred to burrow in the high salinity substrate, irrespective of its beach of origin. Regarding orientation to escape from immersion, Baltic sandhoppers always oriented landwards, whereas Mediterranean sandhoppers showed a significant orientation landwards only when immersed in high salinity sea water. These behavioural traits matched the different environments, and this adaptation capability can be used as a model to analyse the response of a keystone species to environmental changes.