Effects of temperature and salinity on the metabolism and byssal formation of Brachidontes variabilis Krauss (Bivalvia)

Abstract

1. 1. The effects of temperature and salinity on Brachidontes variabilis were studied. Increase in temperature from 27 to 33°C resulted in a net decrease in oxygen uptake. Salinity increments from 47 to 58% resulted in a decrease in oxygen uptake with an apparent stabilization indicating adaptation. Combined increases in temperature and salinity resulted in initial fluctuations in oxygen uptake (either overshoot or undershoot), followed by a return to the pretest rate of oxygen uptake. 2. 2. Nitrogen excretion increased in most of the experiments indicating enhanced utilization of proteins. Correlation was found between byssal formation (percentage of animals forming byssus) and the degree of stress imposed on the animals. 3. 3. Mortality and survival were modified by the salinity regime imposed. Thermal tolerance significantly increased in high salinities. It is suggested that the osmoconforming ability of B. variabilis is responsible for such a relationship. 4. 4. The metabolic plasticity of B. variabilis as expressed in this study is believed to have played a major role in its ability to migrate into the Mediterranean Sea.