GREEN, A.J.; MANAHAN, D.T.: Feeding state, aerobic enzyme activity, and respiration in echinoderm larvae

In this study larvae of the echinoderms Asterina miniata and Lytechinus pictus were raised under different feeding regimes to investigate the relationship between metabolic rate and feeding history (starved to being fed ad libitum). Respiration rates were measured throughout development for comparison to changes in the amount of citrate synthase (CS), a mitochondrial enzyme that is commonly used as a measure of aerobic metabolic capacity. In high-food treatments of 20,000 and 40,000 algal cells ml ^-1, larvae of A. miniata had a strong linear relationship between CS activity and respiration rate (p<0.0001 for both treatments). Larvae reared under low-food environments (0 and 4,000 algal cells ml^-1) showed no significant relationship of CS activity to respiration rate (p = 0.74 and 0.25, respectively). Similarly, for larvae of L. pictus different feeding regimes of 0 and 30,000 algal cells ml^-1 also affected the relationship between CS activity and oxygen consumption (p = 0.64 and 0.0001, respectively). These results show that when larvae are fed high amounts of algae, respiration rates increase proportionately to citrate synthase activity. Larvae that develop with little or no food, however, have no significant relationship between CS activity and respiration rates. CS activity could be a useful index of recent feeding history and physiological state of larvae.