TEMPERATURE ACCLIMATION IN THE COMMON CARP: FORCE-VELOCITY CHARACTERISTICS AND MYOSIN SUBUNIT COMPOSITION OF SLOW MUSCLE FIBRES

Live slow fibre bundles were isolated from the superficial region of the pectoral fin abductor superficialis muscle of common carp {Cyprinus carpio L.) acclimated to either 8 or 20°C. The maximum tetanic tension (Po) of fibre bundles was similar when measured at the acclimation temperature of each group. However, at 8°C, Po was significantly higher in 8°C- than in 20°C-acclimated fish (202 ±8 versus 153±4kNm~2, respectively). For isometric tetani at 8°C, the times to 50 % peak force and from peak force to 50 % relaxation were 15-20 % faster in preparations from cold- than from warm-acclimated carp. Force-velocity (P-V) curves were fitted using a hyperbolic-linear equation. The curvature of the P-V relationship was found to be independent of acclimation temperature. Unloaded contraction velocity (Vmax) was 17 % higher at 8°C in fibres from fish acclimated to 8°C than in fish acclimated to 20°C (1.18±0.04 and 0.98±0.04 muscle lengths s~ \ respect-ively). Calculated values for maximum power output at 8°C were 26.5 W kg"1 for cold-acclimated and 18.0 W kg"1 for warm-acclimated fish