Evolutionary adaptation to temperature in fish muscle cross bridge mechanisms: tension and ATP turnover

1. Force and ATPase activity were measured in skinned, fast muscle fibres isolated from the myotomes of Antarctic, temperate and tropical fish. 2. Maximum isometric tension was inversely related to normal environmental temperature, when measured at −5 to 0°C. When compared within the normal temperature range of each species, tensions were rather similar. 3. In contrast, the muscle fibres of all three species had similar cross bridge cycle times over the entire temperature range studied. This results in a more economical maintenance of force at normal body temperatures in muscle fibres from the Antarctic fish.