Proximate composition of eggs andlarvae of the sand dollar Encope michelini (Agassiz): the advantage of higher investment inplankotrophic eggs

The protein and lipid content of the eggs, fed and starved larvae of Encope michelini were examined in the laboratory and results compared with those of other obligate planktotrophs. The protein and lipid content of the eggs of E. michelini were higher, and the lipid:protein ratios were five to nine times higher than in most other obligate planktotrophs. Increase in larval size and development to the 8-arm stage was accompanied by a decrease in protein and lipid content for starved larvae but an increase for fed larvae. The main advantage of producing planktotrophic eggs with a high protein and lipid content is that it reduces the amount of endogenous food that must be obtained by feeding to construct the complete set of larval arms. This reduces the total time spent in the plankton and thus the risk fiom being eaten. In addition, after a period of food scarcity, a filly developed 8-arm E. michelini larvae would be more efficient at capturing particles than a 4-arm larva fiom smaller eggs with a low protein and lipid content.