Feeding behaviour and metabolic efficiency contribute to growth heterosis in Pacific oysters [Crassostrea gigas (Thunberg)]

Physiological measurements were made on Pacific oysters from controlled crosses between inbred lines. Hybrid individuals were expected to perform better than inbred oysters, for a variety of traits related to feeding behaviour. The oysters were offered a diet simulating natural suspended particulate matter. By quantifying the organic and inorganic fractions of food, faeces and pseudofaeces, various aspects of feeding were elucidated. The results agreed with expectation; on average, hybrid oysters had higher rates and efficiencies of feeding and growth than inbreds. In one experiment there were significant differences between hybrids and inbreds for seventeen out of twenty cases; in another experiment hybrids performed better than inbreds for eight out of sixteen cases. In both experiments, we find significant differences between the reciprocal hybrids, though heterosis for growth is evident for all hybrids. Our experiments therefore confirmed heterosis for growth and hybrid superiority for physiological traits, independent of ration level; emphasised the complexity of these relationships amongst genotypes; and demonstrated the segregation of physiological traits in the F-2 generation. (C) 1999 Elsevier Science B.V. All rights reserved.