The ability of holothurians to select sediment particles and organic

Abstract

Particle selectivity by deposit feeders is an important concept in the ecology of benthic species. The holothu-rians, as deposit feeders, utilise the organic matter that coats sediment and detritical particles as food. Thus, particle size has been proposed as one resource axis along which niche separation can occur in optimal foraging strategy. Interspecific differences in particle size preference are thought to reduce the interspecific competition among benthic deposit-feeder species. The analyses of the digestive contents of the holothurian species that were sampled in two localities of Alge-rian shallow water areas are presented. The results illustrate the specificity of each species: holothurians ingesting the coarse and fine sediment [Holothuria(Holothuria) tubulosa, H.(Roweothuria) poliand H. (H.) stel-lati], and holothurians selecting fine and very fine sediment [H.(Panningothuria) forskaliand H.(Platyperona) sanctori]. Concerning the selectivity of organic matter, H.(P.) forskaliis the most selective species followed by H.(Platyperona) sanctori, H.(H.) tubulosa, H.(H.) stellatiand H.(R.) poli. This feeding behaviour is discussed between species and sites.