Performance of triploid Pacific oysters, Crassostrea gigas (Thunberg). I. Survival, growth, glycogen content, and sexual maturation in yearlings

Abstract

Triploid Pacific oysters ( Crassostrea gigas Thunberg) were produced by treating newly fertilized eggs with cytochalasin B. Triploid and diploid spat were planted in the field and, 1 yr later, sampled during the reproductive period. As measured by cross-sectional area, triploid males produced half as much and triploid females a quarter as much gonad as diploids. Reduced gonadogenesis affected growth and glycogen utilization. Triploids grew linearly through the period of reproduction, whereas diploids grew little until spawning when weight decreased by 64%; growth of diploids and triploids was parallel subsequently. Diploids showed a typical pattern of glycogen utilization, reaching a low of 4.8% glycogen as dry weight prior to spawning and increasing thereafter. Glycogen levels in triploids also declined, but at a slower rate; glycogen in triploids continued to decline for 2 months after the diploid nadir. Triploids had higher survival rates than diploids, but this is probably not a consequence of reduced sexual maturation. Partial reproductive sterility observed in triploid oysters greatly affects reproductive physiology. Triploidy may be a valuable tool in studies of physiological energetics to partition somatic and reproductive effort.