RATES OF ENERGY-CONSUMPTION AND ACQUISITION BY LECITHOTROPHIC LARVAE OF BUGULA-NERITINA (BRYOZOA, CHEILOSTOMATA)

Lecithotrophic larvae of the cheilostome bryozoan, Bugula neritina (L; ), lose metamorphic competence 12 to 24 h after release from the mater nal zooid. The high respiration rate of newly released larvae (mean=30 6.3 pmol O-2 larva(-1) h(-1), range=149.3 to 466.6, n=18 trials, 22.5 degrees C) from adults collected at Link Port, Fort Pierce, Florida du ring the winter/spring of 1990-1991 reflects their active swimming beh avior. The average energy content per larva was 15.24 mJ (range: 13.35 to 20.17 mJ ind(-1), n=5 groups). If all cells have an identical ener gy content and metabolic rate, then 2 and 20% of the total energy cont ent would be consumed by the onset (2 h post-release) and the loss (24 h post-release) of metamorphic competence. Larvae of B. neritina are a composite of both larval and juvenile tissues and the loss of metamo rphic competence may be due to regional depletion of labile energy sto res in transitory ''larval'' cells, particularly the ciliated cells th at comprise the locomotory organ, the corona. Although ''nonfeeding'', B. neritina larvae can acquire nutrients from the environment in the form of dissolved organic materials (DOM) in seawater. Both the amino acid alanine and the fatty acid palmitic acid can be transported from seawater ([S]=1 mu M, 22.5 degrees C). The rates of alanine influx (ap pearance of label in tissue) averaged 0.366 pmol larva(-1) h(-1) and, based on comparisons between rates of solute transport and metabolism, would contribute little (<1% of required energy) to offset the metabo lic demand. The average rate of palmitic acid influx was 4.668 pmol la rva(-1) h-l and, assuming that the measured influx equals the net solu te flux, could account for 21 to 72% of energy requirements. These dat a suggest that the duration of planktonic life of B. neritina larvae i s principally regulated by the amount of endogenous energy stores, but may be modulated by available DOM in seawater.