PROXIMATE COMPOSITION OF EGGS AND LARVAE OF THE SAND DOLLAR ENCOPE MICHELINI (AGASSIZ) - THE ADVANTAGE OF HIGHER INVESTMENT IN PLANKOTROPHIC EGGS

The protein and lipid content of the eggs, fed and starved larvae of E ncope michelini were examined in the laboratory and results compared w ith those of other obligate planktotrophs. The protein and lipid conte nt of the eggs of E. michelini were higher, and the lipid:protein rati os were five to nine times higher than in most other obligate planktot rophs. Increase in larval size and development to the 8-arm stage was accompanied by a decrease in protein and lipid content for starved lar vae but an increase for fed larvae. The main advantage of producing pl anktotrophic eggs with a high protein and lipid content is that it red uces the amount of endogenous food that must be obtained by feeding to construct the complete set of larval arms. This reduces the total tim e spent in the plankton and thus the risk from being eaten. In additio n, after a period of food scarcity, a fully developed 8-arm E. micheli ni larvae would be more efficient at capturing particles than a 4-arm larva from smaller eggs with a low protein and lipid content.