Résumé:
This study of the diet of three species of holothurians (H. poli, H. tubulosa and H. arguinensis) from the coastal fringe of Mostaganem (Salamander and Stidia), was carried out during the spring season for the purpose of appreciating the selective capacity for the various foodstuffs and to analyze the rate of the organic matter at the level of the contents of their digestive tubes and in the sediments of their biotopes. The food resources consumed by the Holothurians studied are made up of an animal fraction (Foraminifera, Sponge spicules, Mollusks, Sea Urchin spines, Nematodes, Crustacea and Holothurian spicules) and another plant fraction (Diatoms, Algae, Posidonia and Cyanophyceae). Foraminifera, Diatoms and Sponge Spicules are the main foods consumed by these species studied (with 15.42%, 28.75% and 22.08% respectively in H. poli; with 18.33%, 51.67% and 15% respectively in H. tubulosa; with 28. 33%, 30% and 16.67% respectively in H. arguinensis at the Salamander site), also at the Stidia site (with 16.67%, 31.67% and 10.42% respectively in H. poli; with 23.33%, 10% and 13.33% respectively in H. tubulosa). The obtained results on the selectivity in the choice of food for holothurians through the calculation of the electivity index (E’) Ivlev was carried out, at the Salamander site H. poli shows a preference for sponge spicules, Diatoms and Holothurian spicules, H. tubulosa prefers Cyanophyceae, Posidonia and Algae, sponge spicules, Mollusks and Crustacea are selected by H. arguinensis. On the other hand, at the Stidia site: H. poli and H. tubulosa showing a preference for Nematodes, Algae and Posidonia.
An analysis of the rate of organic matter at the level of the first section of the digestive tract of holothurians, of the sediments of their biotopes, was carried out in order to appreciate the selectivity in feeding in these species. The results obtained during this work on the two sites, show that the percentage of the rate of organic matter at the level of the Forgut presents high results in relation to the sediment of the biotope, for the species H. poli, H. arguinensis and H. tubulosa.
