Local feeding behavioural responses to food availability of the amphipod Orchestoidea tuberculata

Abstract

The main food sources in sandy beaches are stranded animals and seaweeds. In species with low dispersal potential or reduced mobility, it is expected that local adaptations or plastic responses arise to confront these environments and maximize fitness. Orchestoidea tuberculata is a common semi-terrestrial talitrid amphipod in Chilean sandy beaches and shows a very limited dispersal, with direct developmental mode and reduced mobility at the adult stage. O. tuberculata feeds on stranded seaweeds and organic material from animal origin during low tides. The effects of different diets on food preference, growth rate and survival of O. tuberculata individuals from two sandy beaches with different types of food availability were evaluated: Punta Hualp & eacute;n with high abundances of stranded seaweed and animals, and Lenga showing low levels of stranded seaweeds, and high levels of food of animal origin. To evaluate potential local responses in feeding behavior, individuals of O. tuberculata from both localities were fed with algae (Durvillaea incurvata) and animal carcasses (Emerita analoga) disposed in separate and mixed diets (D. incurvata + E. analoga). Results showed that food preference in O. tuberculata varies between individuals from the two sites. Individuals tended to show the highest performances with the diet composed of the most common dietary item available in their site of origin (algal or animal). These results may indicate the existence of potential local adaptations or feeding behavior plasticity in O. tuberculata as responses to the spatial variability of food availability observed in sandy beach ecosystems.