Metabolism and chemical composition of phyllosoma larvae, with special reference to the tropical rock lobster Panulirus ornatus (Decapoda; Palinuridae)

Rates of oxygen consumption and ammonia excretion and chemical composition (water, ash and CN composition) were determined throughout larval development, from Stages I–IX, of Panulirus ornatus phyllosoma larvae raised in the laboratory. Dry mass (DM) specific oxygen consumption rates varied from 1.4 to 3.3 μl O 2 (DM) −1 h −1, showing a pattern of developmental decline. In contrast, specific ammonia excretion rates fluctuated irregularly from 0.02 to 0.067 μg NH 4–N (DM) −1 h −1, yielding oxygen consumption to ammonia excretion ratios (O:N atomic ratio) as wide as 51–180. With progressive development, ash decreased from 34% to 17% of DM while C composition increased from 33% to 41% of DM. No consistent changing pattern with development was seen for water contents (74–83% of WM), N composition (6.9–9.5% of DM) and C:N ratios (4.0–5.1). Supplemental data of both specific oxygen consumption and ammonia excretion rates of laboratory-raised Stage III P. homarus and wild Parribacus antarcticus phyllosoma (stage unknown) of this study and literature data on phyllosomas of other lobster species by previous workers were shown to be comparable to those of P. ornatus phyllosomas when the differences in DM and temperature were taken into account. No appreciable differences due to the origin of the specimens, whether wild or laboratory-raised, were evident. Comparison of the present results with those of stomatopod larvae and holoplanktonic crustaceans in the same tropical marine habitats revealed that phyllosoma larvae are characterized by somewhat lower DM specific oxygen consumption rates and N composition. The study revealed markedly reduced ammonia excretion rates in phyllosomas, suggesting reduced swimming activity and preferential utilization of dietary protein to somatic growth rather than metabolism. ► As zooplankton phyllosoma larvae have lower specific ammonia excretion rates. ► This suggests less utilization of dietary protein to their metabolism. ► Their body composition is characterized by lower N contents. ► This is indicative of their reduced swimming activities.