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 described 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 clearest relationship 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 between the asymmetry and the growth rate. The existence and interpretation of both of these phenomena have led to many publications.Original Abstract: Grace a un echantillonnage d'huitres juveniles a vitesses de croissance differentes (faible, moyenne et forte), une etude biometrique fine de l'evolution de la coquille est realisee en distinguant les deux valves. On peut en conclure que l'ensemble des phenomenes est domine par la mise en place precoce d'une asymetrie directionnelle qui rapidement est suffisamment forte pour qu'on puisse parler de dissymetrie. La principale relation mise en evidence se revele etre celle entre la faiblesse du taux de croissance et l'importance de la dissymetrie relative du poids des valves. Ce resultat est a mettre en parallele avec la relation, d'ailleurs tres discutee, entre asymetrie et taux de croissance dont l'existence et l'interpretation ont donne lieu a de nombreuses publications.