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The energy required for development was measured in two closely related echinoids with differing modes of development. Heliocidaris tuberculata hatches from a 95-{mu}m egg (~0.1 {mu}g dry organic mass) and develops via a planktotrophic larva over 21-30 days into a juvenile (5.3-7.5 {mu}g). H. erythrogramma hatches from a ~400 {mu}m egg (11.6-19.0 {mu}g) and develops over 3.5-4 days via a lecithotrophic larva into a juvenile with a mass not detectably different from that of the egg. Oxygen consumption increased exponentially in H. tuberculata and peaked at about 200-500 pmol indiv-1 h-1, whereas the oxygen consumption of H. erythrogramma increased rapidly, reaching a plateau at about 800 pmol indiv-1 h-1 on the second day. Metabolic energy expenditure for development to metamorphosis was twofold higher for H. tuberculata (52-60 mJ indiv-1) than for H. erythrogramma (26-35 mJ indiv-1). The interspecific comparison suggests that about half the metabolic expenditure for planktotrophic development goes toward building and operating the larval feeding apparatus and that the return on this investment is 400%-600% over the larval period. When the energy equivalents of the organic masses of the juveniles are included, the energy for constructing a juvenile on a per mass basis is essentially the same for both species (cf. H. tuberculata: 37-42 mJ {mu}g-1; H. erythrogramma: 34-36 mJ {mu}g-1) and implies the absence of developmentally based energetic barriers or benefits to changes in modes of development. Substantial amounts of metabolically inactive material may be present in embryos with nonfeeding development and should be considered in physiological measurements and comparisons.

Energy Use During the Development of a Lecithotrophic and a Planktotrophic Echinoid