Fig. 6. Total cost of transport (TCOT), the amount of energy expended per unit mass per unit distance, as a function of swimming speed for the triggerfish Rhinecanthus aculeatus and the parrotfish Scarus schlegeli. TCOT was calculated from the relationship between total _O2 and swimming speed presented in Figs 4A and 5A. Lines in blue are for median-paired fin (MPF), rigid-body swimming, and the line (triggerfish) and symbols (parrotfish) in red are for body-caudal (BCF), undulatory swimming. Symbols for parrotfish BCF swimming are the same as in Fig. 4.