Oyster adenylate energy charge: response to levels of food

Abstract

Adenylatc Encrgy Charge (AEC) values of Crassostrea gigas (9 and 18 months old) cultured in ponds in Marennes-Oleron Bay (Atlantic coast, France) are reported. Two ponds were loaded with two different initial oyster biomasses in order to obtain different food conditions. The growth of oysters was different in the two ponds which corroborated the effectivences of attaining different food conditions. AEC level was different depending on the pond and was therefore related to food availability per unit oyster biomass. Well-fed oysters exhibited greater AEC values than poorly-fed oysters, throughout thc study. Information on nutritional situations for wild or cultured populations can therefore be obtained by AEC. In cach pond, the seasonal AEC variations were similar for both age-groups and were characterized by a minimum value in summer and a maximum value in wintcr. The influence of reproduction on these variations cannot be ruled out as for al1 the batches maturation processes were evidenced. Research will be done on a temperature effect to try to distinguish these seasonal variations. A strong correlation between adenylatc energy charge (AEC) and guanylatc encrgy charge (GEC) was demonstrated; it was similar for both ponds. The levecs of nucleotide concentration were relatively stable during the survey cxcept in September and December for oysters in the low density pond. Among nucleotides, adenylate pool represented the major part (80%). A decrease in the total concentration of adenylates was observed in August. The best growth correlated with the lowest adenylate perccntage and a better GTP/ATP ratio, suggesting that this ratio could be a useful index for growth.