Fish swimming: Patterns in muscle function

Undulatory swimming in fish is powered by the segmental body musculature of the myotomes. Power generated by this muscle and the interactions between the fish and the water generate a backward-travelling wave of lateral displ acement of the body and caudal fin. The body and tail push against the wate r, generating forward thrust, The muscle activation and strain patterns tha t underlie body bending and thrust generation have been described for a num ber of species and show considerable variation. This suggests that muscle f unction may also vary among species. This variation must be due in large pa rt to the complex interactions between muscle mechanical properties, fish b ody form, swimming mode, swimming speed and phylogenetic relationships. Rec ent work in several laboratories has been directed at studying patterns of muscle power output in vitro under simulated swimming conditions. This work suggests that the way that fish generate muscle power and convert it into thrust through the body and caudal fin does indeed vary, However, despite t he differences, several features appear to be common to virtually all speci es studied and suggest where future effort should be directed if muscle fun ction in swimming fish is to be better understood.