Temporal and spatial variability in the feeding behavior of the black sea urchin Arbacia lixula (Echinodermata: Echinoidea) from the north-western Algerian coast

Abstract

The black sea urchin Arbacia lixula (Linnaeus, 1758) is one of the most domi-nant echinoids in the sublittoral communities of the Mediterranean Sea, where it is considered an essential structuring species by its grazing activity. The present work is considered to be the first study to address the diet of the species A. lixula in Algeria. This study aims to perform on the one hand; a temporal monitoring of the food preferences of two populations of A. lixula living in two different sites in shallow water (port of Salamandre, Stidia) on the coast of Mostaganem (Algeria) during the years 2015 and 2016, and on the other hand; get an idea of the variations of the different trophic sources used and appreciated by this echinoid. The quantitative and qualitative aspect is achieved by monitoring the evolution of the repletion index as well as the identification of the items present in the digestive contents by the contact method of Jones (1968). The results of this monitoring showed that it is an opportunistic species which adapts its diet according to the quality and quantity of food available. Arbacia lixula prefers encrusted coralline algae with a large faunal fraction. In areas rich in nutrients, the spines of these sea urchins may elongate to half the diameter of the test. Based on the results, A. lixula can be associated with habitat, seasonal changes or other specific environmental parameters that merit further development in order to fully understand its functioning in marine ecosystems.