ENERGY USE DURING THE DEVELOPMENT OF A LECITHOTROPHIC AND A PLANKTOTROPHIC ECHINOID

The energy required for development was measured in two closely relate d echinoids with differing modes of development. Heliocidaris tubercul ata hatches from a 95-mu m egg (similar to 0.1 mu g dry organic mass) and develops via a planktotrophic larva over 21-30 days into a juvenil e (5.3-7.5 mu g). H. erythrogramma hatches from a similar to 400 mu m egg (11.6-19.0 mu g) and develops over 3.5-4 days via a lecithotrophic larva into 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 build ing and operating the larval feeding apparatus and that the return on this investment is 400%-600% over the larval period. When the energy e quivalents of the organic masses of the juveniles are included, the en ergy for constructing a juvenile on a per mass basis is essentially th e same for both species (cf. H. tuberculata: 37-42 mJ mu g(-1); H. ery throgramma: 34-36 mJ mu g(-1)) and implies the absence of developmenta lly based energetic barriers or benefits to changes in modes of develo pment. Substantial amounts of metabolically inactive material may be p resent in embryos with nonfeeding development and should be considered physiological measurements and comparisons.