A DELTA-C-13 STUDY OF THE FEEDING-HABITS IN 4 MEDITERRANEAN LEPTOMYSIS SPECIES (CRUSTACEA, MYSIDACEA)

Mediterranean Leptomysis species are bentho-nectonic shrimps living close to seagrass bed bottoms, forming swarms during the day and feeding on detritus and sedimentary organic matter during the night. As this matter is derived from different plant sources (phyloplankton, seagrasses, macro- and microalgae), assimilated carbon entering mysid tissues can hardly be identified on the basis of digestive tract analyses. Stable carbon isotope ratio measurements help to delineate food sources of the different studied Leptomysis species because plants are distinct isotopically. These delta(13)C measurements reinforce the view of the minor role of seagrass carbon in benthic food webs and of the importance of algae in the dynamics of these ecosystems.