The action of muscles in swimming fish.

Abstract

This review will focus on the mechanical performance of the trunk muscles of fish in relation to their important role in the generation of lateral undulations during swimming. In most fish, the different muscle fibre types are located in separate regions in the trunk (e.g. Boddeke, Slijper & Van der Stelt, 1959). This makes fish muscle particularly suitable for investigating how different fibre types are used during locomotion. Not only can the activity of homogeneous fibre bundles be detected fairly easily by electromyography (e.g. Bone, 1966), but bundles of fibres of the same type may also be isolated for mechanical experiments which mimic the in vivo activation and strain variation (e.g. Altringham & Johnston, 1990a). The following questions will be addressed in particular. First, a swimming fish produces waves of curvature along its trunk with its muscles. What is the nature of the associated net bending moments along the trunk and how much power is produced along the trunk (section 2)? Second, what are the mechanical properties of muscle fibres of fish and what is their efficiency (sections 3 and 4)? How are the muscle fibres at different positions in the trunk of a swimming fish recruited during various swimming modes? What is their in vivo work and power output (section 5)? Space limits do not allow consideration of the structural design of the myomeres, nor the complex innervation patterns of fish muscles.