Meeting Abstract

6.5  Tuesday, Jan. 4  PROTEIN METABOLISM AND GENOTYPE-DEPENDENT DIFFERENTIAL GROWTH OF BIVALVE LARVAE LEE, JW*; MEYER, E; MANAHAN, DT; University of Southern California jimmylee@usc.edu

High growth variance is commonly observed for animals growing under identical environmental conditions. The physiological and genetic basis of such variability is still poorly understood. In this study different families of bivalve larvae (Crassostrea gigas) were produced from factorial crosses of adults of known genetic lines. Our goal was to understand the biochemical basis of environmental-genotype growth interactions. Larval families of different genotypes were reared under the same environmental conditions (food, temperature). Conversely, larvae of the same genotype were reared under a different environmental condition (temperature). When reared under the same conditions, larval families from a cross of line-5 by line-3 (sire by dam) had faster growth than other families from the same lines (3×3; 3×5; 5×5). The 5×3 family had the fastest growth rate, with a 1.9-fold greater protein content by 10d than the reciprocal hybrid 3×5 family (5×3 = 56±5 ng/larva; cf. 3×5 = 30±2 ng/larva). Age-specific protein synthesis was not different among larval families growing at different rates, but protein depositional efficiency was different (PDE = ratio of protein accreted to amount synthesized). The faster-growing 5×3 family had a PDE of 74%, compared to only 45% for the slower-growing reciprocal family (3×5 cross). When larvae of the same family were reared at 25ºC and 20ºC, protein synthesis increased as expected at the higher temperature (25ºC is considered optimal for larvae of this species). Larval growth at this ‘optimal’ temperature had, however, up to 2.3-fold lower PDE. We conclude that protein turnover – not synthesis – determines genotype-dependent differential growth and that PDE appears to be a key metabolic regulator of phenotypic growth variance.