Dissymmetry and growth rate of the shell valves in the juveniles of the oyster Crassostrea gigas Thunberg.

Thanks to a sampling of juvenile oysters with different growth rates (slow, medium and fast), a subtle biometrical study of their shell evolution is d escribed distinguishing the two valves. We conclude that all the phenomena are dominated by the early establishment of a directional asymmetry, which rapidly becomes so large that we should consider dissymmetry. The dearest r elationship is revealed to be that between the weakness of the growth rate and the degree of the relative dissymetry between the weights of the valves . This result is to be compared with the highly debated relationship betwee n the asymmetry and the growth rate. The existence and interpretation of bo th of these phenomena have led to many publications. (C) 2000 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.