Absorption efficiencies of Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea) for selected marine plants

Abstract

The absorption efficiencies of the sea urchin Lytechinus variegatus (Lamarck) were calculated by an indicator method. Absorption efficiencies for total organic material, protein, lipid, and carbohydrate were highest with Halimeda incrassata Ellis as food (43 %, 65 %, 71 % and 35 %, respectively), and lowest with Eucheuma isiforme C. Agardh as food (−35%, −42%, −56%and −34%, respectively). Moderately positive absorption efficiencies for total organic material were found with Thalassia testudinum König & Sims and Ulva lactuca L. as food, and low positive absorption efficiencies for total organic material are found with Syringodium filiformis Kützing and Sargassum sp. as food. Absorption efficiencies of the sea urchin Strongylocentrotus purpuratus (Stimpson) (calculated from the literature) were much greater than those of Lytechinus for carbohydrate, but less for protein and lipid. Both sea urchins showed negative efficiencies for some nutrient fractions of their foods. The absorption index (mg nutrient fraction absorbed/g dry wt ingested) showed that Thalassia supplied the most protein and total organic material (43 mg/g dry wt ingested and 142 mg/g dry wt ingested, respectively). In general, the absorption indices indicate that Lytechinus obtains more protein and lipid, but less carbohydrate from its food than does Strongylocentrotus. In the field Lytechinus has primarily a detrital diet.