The role of elastic energy storage mechanisms in swimming: an analysis of mantle elasticity in escape jetting in the squid, Loligo opalescens

Abstract

Elastic energy storage mechanisms have been shown to improve locomotory performance and efficiency in many animals. In this paper we consider the role of elastic energy storage in jet locomotion of the squid, Loligo opalescens. The jet is powered by the contraction of circular muscles in the mantle. In addition, the mantle contains a collagen fibre based energy storage system (the mantle "spring") which captures some of the mechanical energy produced by the circular muscles and then releases this energy to power the refilling of the mantle cavity. The mantle spring is constructed so that it stores energy from the circular muscles only at a time in the jet cycle when, by virtue of the cylindrical geometry of the mantle, the circular muscles are unable, to apply their full mechanical output to the generation of hydrodynamic thrust. Thus the mantle spring increases the utilization of the circular muscles, and our analysis indicates that these muscles are used at virtually 100% of their potential through the entire jet. Presumably this increase in muscle utilization improves the locomotory performance of the squid. Other swimming animals, such as fish, may obtain similar benefits if elastic energy storage systems are constructed to capture energy at a time in the swimming cycle when muscles can not apply their full output to the generation of useful hydrodynamic forces.