Article ID: 19-00015
The long-spined sea urchin Diadema setosum is assumed to contribute to rocky-shore denudation. In order to investigate their natural diets, D. setosum was reared for one year with exclusive feeding of a brown alga Ecklonia cava, and digestive enzyme activities and carbon and nitrogen stable isotope ratios were compared between the reared and wild individuals. No notable growth was observed in the reared individuals. Specific activities in 11 of 13 digestive enzymes of reared individuals were significantly higher than those of wild individuals. The nitrogen stable isotope ratio of the reared individuals was significantly higher than that of the wild individuals, and the trophic level (3.23) of the wild D. setosum indicated a carnivorous diet (higher consumers). These findings indicate that D. setosum is omnivorous and may depend more on animals than plants.
