A GENETIC AND METABOLIC BASIS FOR FASTER GROWTH AMONG TRIPLOIDS INDUCED BY BLOCKING MEIOSIS-I BUT NOT MEIOSIS-II IN THE LARVIPAROUS EUROPEAN FLAT OYSTER, OSTREA-EDULIS L

This study establishes a genetic and metabolic basis to faster triploi d growth in the oyster Ostrea edulis. Triploidy was induced using cyto chalasin B, and image analysis of biopsied tissue employed to ensure s imilar ploidy of all animals within each class. Results indicate that lifetime growth in total dry tissue weight over 15 months was more tha n 60% faster (p<0.001) in meiosis I triploids than in diploid siblings or meiosis II triploids, with no difference between meiosis II triplo ids and their diploid siblings. For six polymorphic enzyme loci, singl e-locus heterozygosity was consistently greatest in meiosis I triploid s (p<0.001), so that average multiple-locus heterozygosity in meiosis I triploids was 49% higher than in normal diploids, and 55% higher tha n in meiosis II triploids (p<0.001). This suggests that faster growth resulted from increased allelic diversity, rather than the increased a llelic quantity that results from the addition of one entire set of ch romosomes among triploids generally. Results also confirm that the fas ter growth of meiosis I triploids resulted from reduced energy expendi ture, associated with lower concentrations of RNA per unit total tissu e protein, which infer reduced rates of whole-body protein turnover. S tatistical analyses confirmed that differences in oxygen consumption a nd growth were associated with both ploidy class and average multiple- locus heterozygosity, indicating that performance in meiosis I triploi ds is not only improved as a result of reduced reproductive output, bu t also through the metabolic consequences associated with increased he terozygosity.