Feeding and decoration preferences of the epialtidae crab Acanthonyx scutiforms

Abstract

Studies on the feeding preferences of marine herbivores are very important for our better understanding of the biology and the ecological role of these organisms. Members of the family Epialtidae are usually herbivores that mask themselves with pieces of seaweed and other materials to avoid predation. In order to better understand the mechanisms of food and decorating choices of the decorator crab Acanthonyx scutiformis, two multiple-choice feeding assays were performed using fresh seaweeds and artificial food containing crude extracts of the four seaweeds Osmundaria obtusiloba, Plocamium brasiliense, Sargassum sp., and Dictyota menstrualis, offered simultaneously to this crab species. In both assays the seaweed most consumed was O. obtusiloba, followed by P. brasiliense and Sargassum sp., while D. menstrualis was the least consumed. It is suggested that A. scutiformis is a generalist feeder, but with some preference for the perennial red seaweed O. obtusiloba and the chemically-defended seaweed P. brasiliense. Decorating behavior observations revealed the preferences of A. scutiformis by P. brasiliense. This decorating behavior can be interpreted as a mechanism to avoid generalist predators, since feeding and decorating preference were not associated and the crab used only small pieces of chemically defended algae.