Thermal acclimation by Mytilus edulis l.

The routine oxygen consumption, ventilation and filtration rates of Mytilus edulis, maintained at various food levels, are shown to acclimate in the laboratory to high and low temperatures. Complete acclimation occurs in approximately 14 days. The physiological parameters, oxygen consumption, feeding rate and assimilation efficiency are determined during the process of thermal acclimation and then integrated by means of the balanced energy equation. An 'index of energy balance' is proposed to quantify the degree of stress imposed during and after acclimation to high and low temperatures. The upper thermal limits of complete metabolic compensation occurs between 20 and 25o0. The breakdown in the animal's ability to acclimate is shown to result in a markedly reduced index of energy balance (or scope for growth). The temperature dependence and acclimation of metabolism and activity are described for Mytilus edulis. The three levels of metabolism (standard, routine and active) and the degree of activity are characterized by different temperature coefficients (Q-10). Evidence suggests that this differential temperature response may be partly explained in terms of activity, and that acclimation of routine oxygen consumption is mainly a direct consequence of the compensation of filtration rate. The effects of temperature and food on the components of the respiratory system (heart rate, ventilation rate and oxygen uptake) are investigated. There is no thermal acclimation of heart rate, and no apparent close coupling of heart rate with either ventilation or metabolic rate. Radioisotope tracer experiments and quantitative biochemical analysis of tissues have been used to study some biochemical changes that occur in response to temperature. During the process of warm acclimation, the digestive gland reserves appear to be utilized. There was, however, no apparent fundamental metabolic reorganization during thermal acclimation.