Effect of temperature on oxygen consumption and ammonia excretion in the Calafia mother-of-pearl oyster, Pinctada mazatlanica (Hanley, 1856)

The effect of temperature on oxygen consumption and ammonia excretion in the pearl oyster Pinctada mazatlanica was studied as a strategy to define the optimum thermal range for experiments on reproductive conditioning of broodstock of this species. Oysters were taken to the laboratory, acclimated for 2 weeks at four temperatures (18, 23, 28, and 33 degreesC), and transferred to respiration chambers for individual measurements of oxygen consumption and ammonia excretion at the same temperatures. Respiration and excretion rates, as well as routine respiratory/excreted energy and Q(10) coefficients were calculated. One-way ANOVA was applied to determine differences in these parameters as a function of temperature. All physiological parameters yielded highly significant differences with increasing temperature, suggesting that an adequate metabolic temperature range for the species may lie between 23 and 28 degreesC. Within this range, a combination of active respiration and low ammonia excretion, together with Q, 0 coefficients near 2, suggest the existence of compensatory mechanisms that allow the species to perform seasonal regulation during moderately warm temperature changes. In contrast, 18 and 33 degreesC represented marginal temperature conditions close to the tolerance limits of the species. In particular, 33 degreesC was a stressful temperature for P mazatlanica because of high ammonia excretion. More studies under conditions of satiation and hypoxia, as well as experiments testing lower and higher lethal temperatures are needed to understand the energy budget of the species. (C) 2004 Elsevier Science B.V. All rights reserved.