Final answer:
Fish use both compact and spongy myocardium to oxygenate their heart muscle.True
Step-by-step explanation:
True.
Fish oxygenate their heart muscle using both compact myocardium with coronary vessels and spongy myocardium. The fish have a two-chambered heart that pumps blood to the gills for oxygenation and then circulates it through the rest of the body. The compact myocardium and coronary vessels provide oxygenated blood to the heart muscle, while the spongy myocardium helps with oxygenation and circulation.