Muscle Structure

In land animals, individual muscles and muscle fibers can be quite long, on the order of several inches, and the muscles taper down at the ends into a tough tendon that connects them to bone. In fish, by contrast, muscle fibers are arranged in sheets a fraction of an inch thick (“myotomes”), and each short fiber merges into very thin layers of connective tissue (“myosepta”), which are a loose mesh of collagen fibers that run from the backbone to the skin. The muscle sheets are folded and nested in complex W-like shapes that apparently orient the fibers for greatest efficiency of force transmission to the backbone. There are about 50 muscle sheets or “flakes” along the length of a cod.