ABSTRACT
Egg size (volume) determines the mode of larval development in that small, nutrient poor eggs give rise to feeding larvae and large, nutrient rich eggs give rise to nonfeeding larvae or brooded development. However, some eggs are far larger than necessary to insure successful larval development and they produce relatively large juveniles suggesting that investment in energy rich eggs may affect juvenile growth and survivorship. We have experimentally manipulated the directly developing embryos of the sea urchin Heliocidaris erythro gramma to remove their extensive lipid reserves, reducing dry organic weight by 40% and original egg volume by over 50%. In replicated comparisons between normal and reduced-lip id siblings, there was no significant difference in developmental time to metamorphosis or in percent metamorphosis. Juveniles metamorphosed after 3.5 to 4 days at 22 degree C. and those from control (untreated) embryos had mean test and total diameters of 430 and 665 urn, respectively. Juveniles from reduced-lip id embryos had a full complement of body parts but were approximately 13.5 % smaller in test diameter and 8% smaller in total diameter. Juveniles from control eggs grew in test diameter; those from the reduced-lipid treatments did not. Spines of both types of juveniles grew, but spine growth of control juveniles was significantly faster and persisted for a longer time than that of juveniles from reduce-lipid embryos. Control juveniles survived longer than their reduced-lipid siblings. Supported by NSF grant INT-9114655.
