Thermal Responses Reflect Protein Turnover in Mytilus edulis L.

Abstract

Relationships between whole-body protein turnover and energy metabolism are defined from studies of 15 individual Mytilus edulis L. Differences in protein metabolism are shown to affect growth rate, temperature sensitivity of metabolic rate, rate of thermal acclimation and ability to survive high temperatures. Faster growth in individuals fully acclimated at 100C derived primarily from reduced metabolic requirements associated with lower intensities of protein turnover. Protein turnover may also have amplified metabolic responses upon transfer of mussels from 10 to 200G, for accompanying increments of both protein synthesis and oxygen uptake were proportionally higher among slower-growing individuals. These same individuals subsequently implemented the greatest daily savings in energy expenditure, so that complete thermal acclimation had been effected within 14 days. Slow-growing mussels with the fastest intensities of protein turnover at 100C were also the first to die following a further increase from 20 to 28 5 G. This reflected their greater temperature sensitivity; elevated metabolic demands apparently exceeding a critical threshold. We suggest that these differences are genotype-dependent but emphasize that relative fitness advantages of differential protein turnover may vary according to specific circum-