Temperature adaptation in sea anemones: Physiological and biochemical variability in geographically separate populations of Metridium senile

Latitudinally separate populations of the sea anemone Metridium senile (L.) are very similar genetically by electrophoretic criteria, yet respond differently to temperature. Anemones from southern and northern California (USA) have different oxygen consumption patterns in response to acclimatory and acute changes in temperature. Northern anemones show a pronounced increase in Q₁₀ at temperatures just above the normal environmental range, but southern anemones do not. The two populations also differed in the extent of metabolic compensation to temperature following several weeks of acclimation. This acclimation regime resulted in changes in the activities of several enzymes of intermediary metabolism, yet the extent and direction of these changes did not display a consistent trend with regard to acclimation temperature or population. The biochemical concomitants of acclimatory and acute temperature effects were studied further by measuring the concentrations of adenylates (ATP, ADP, and AMP) in anemones from the two populations exposed to different temperature regimes. During cold acclimation for several weeks, total adenylate concentrations (A_T) increased in both the southern and northern populations, possibly due to metabolic rate compensation, since A_T is positively correlated with tissue metabolic rate in many species. Moreover, the extremely low weight-specific oxygen consumption rates of M. senile are probably related to its very low A_T values. Acute temperature decreases had no effect on adenylate concentrations and adenylate energy charge (AEC); in contrast, acute temperature increases led to large changes in adenylate concentrations. The effects of starvation on adenylate concentrations are pronounced, and the effect is temperature-dependent. In starved individuals held at 20°C, AEC values fell to 50% of normal values after 8 d, while those held at 10°C maintained normal AEC values.