MORAN, A.L.*; MANAHAN, D.T.: Energy metabolism during larval development of two abalone species, Haliotis fulgens and H. sorenseni

Lecithotrophic larvae of marine organisms develop to metamorphosis without feeding on plankton. An understanding of the biochemical and physiological energetics of lecithotrophic development is useful for interpreting patterns of larval development and dispersal. This study investigates the metabolic rates and biochemical constituent utilization of two species of abalone, and compares these data to other congeneric marine species. Larvae of the green abalone, Haliotis fulgens, utilized triglycerides as a primary source of endogenous energy reserves, with 50 percent depletion during the 9-day period of larval development at 15 ºC. The amount of phospholipids remained constant and total protein content decreased by 25 percent. After embryogenesis, larvae of H. fulgens had oxygen consumption rates of 78.2 ± 3.6 pmol larva^-1 hr^-1 through subsequent development. An energy budget analysis revealed that the rate of loss of biochemical reserves balanced respiratory needs. Larvae of H. sorenseni (the white abalone) were examined during later larval development and had a respiration rate of 58.9 ± 4.7 pmol larva^-1 hr^-1 at 13 ºC. The range of metabolic rates of both of these species of abalone are similar to published data for the larvae of a congener, H. rufescens. This suggests that larval metabolism and energy utilization may be evolutionarily conservative within genera and developmental modes. Differences in energy utilization between closely-related species such as those in this study are likely due to (1) different egg composition between species and spawns, and (2) variations in rearing conditions (e.g., water quality).