Fig. 1. (A) Structure of the myotomes in side or fillet view. This diagram shows three myotomes each separated by the removal of two intervening myotomes to demonstrate the nested nature of the cones. The silhouette of the fish indicates the orientation of the myotomes within the fillet. Each anterior-pointing cone is indicated with a white arrow and each posterior-pointing cone is indicated with a black arrow. (B) Diagram of the myotomes from a generic non-heterothermic fish in cross section, or steak view. The red, oxidative muscle is in a small wedge in close apposition to the skin along the mid-lateral line (indicated in orange). The remainder of the muscle consists of white, glycolytic fibers within the cones. Sectioning through the nested cones produces the concentric ring structure visible in this view (white arrows). (C) Diagram of the myotomes of a heterothermic yellowfin tuna (Thunnus albacares) in cross section, or steak view. This diagram shows the distribution of red muscle that is common to tunas, where there is an internal loin of red muscle fibers (in red) in addition to the superficial wedge of red fibers seen in other fish (orange). The location where the mid-lateral septum passes through this section is indicated with a white arrow.

Return to article