| Summary: | Swimming is important to the ecology of many species of scallop but the effects of temperature upon swimming are not clear. The ecology and natural history of scallops is introduced followed by a description of the state of current knowledge of scallop swimming, muscle physiology and energetics. The effects of temperature and the mechanisms used by ectotherms to compensate for such changes over acute, seasonal and evolutionary timescales are discussed. Scallops are active molluscs, able to escape from predators using jet propelled swimming. Queen scallops (Aequipecten opercularis) were acclimated to 5,10 and 15°C in the laboratory and collected in Autumn (13±3°C) and Winter (8±2°C) in order to investigate seasonal acclimatisation. The first jetting cycle of escape responses in these animals was recorded using high-speed video (200-250fps). Whole-animal velocity and acceleration were determined while measurements of valve movement and jet area allowed the calculation of muscle shortening velocity, force and power output. Peak swimming speed was significantly higher at 15°C (0.37m.s⁻¹) than at 5°C (0.28m.s⁻¹). Peak acceleration was 77% higher at 15°C (7.88m.s⁻²) than at 5°C (4.44m.s⁻²). Mean cyclic power output was also higher at 15°C (31.3W.kg⁻¹) than at 5°C (23.3W.kg⁻¹). Seasonal comparison of swimming in freshly caught animals revealed significantly greater acceleration (x2 at 11°C) and velocity during jetting in Winter than in Autumn animals (ANCOVA). These were associated with significant increases in peak power output (x8 at 11 °C), force production and muscle shortening velocity. Actomyosin ATPase activity was significantly higher (31 % at 15°C) in winter animals with peptide mapping of the Myosin heavy chain showing no differences between groups. Increases in muscle power output were associated with reductions in the length of the jetting phase as a proportion of the overall cycle. As a result large changes in muscle performance resulted in large short-term whole body performance enhancement but little ...
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