Changes in carbohydrate, lipid, and protein levels with age and season in the sand dollar Mellita Quinquiesperforata

The seasonal levels and amounts of carbohydrate, lipid, and protein were determined for the gonad, gut, epithelium with spines, and test of young and old Mellita quinquieperforata (Leske). These biochemical constituents were evaluated in relation to the nutrient reserves, body shape, energy requirements, and habitat of the animal. Results indicated that young animals have gonad and gut indices which are twice as great as older animals. Gonad and gut indices show similar cyclic changes, with gonad indices reaching a peak in March and April. The gonadal carbohydrate level is highest (36%) during early maturation. As the gonads continue to mature, levels of carbohydrate decrease and levels of lipid and protein increase. Carbohydrate appears to be stored in the gonad. There are significantly greater amounts of lipid and protein in the epithelium with spines and in the test of younger sand dollars as compared to older sand dollars. Differences in biochemical composition between ovaries and testes are not significantly different during the spawning season. Increased water temperatures in summer are associated with mass mortalities of older animals. It would appear that older animals are not as nutritionally ‘fit’ as younger animals because of lower nutrient reserves and increased respiration at high water temperatures.