Cardiac morphology & anatomy in fishes and the associated coronary circulation

Abstract

This article reviews the anatomy of the fish heart and its coronary circulation in relation to their functions. The shape, size and anatomy of the cardiac chambers vary greatly among species but, in general, the venous blood enters to sinus venosus from ductus Cuvier. The sino-atrial canal connects the sinus venosus to the atrium, which pumps blood to the ventricle. The ventricle is the largest cardiac chamber by mass and the most muscular. Blood is pumped from ventricle into an arterial outflow vessel, either a bulbus arteriosus or a conus arteriosus. The shape and the size of cardiac chambers are mainly influenced by their function and how they fit into the fish's body shape. In most fish species the ventricle is composed solely from spongy myocardium, but some fish species have compact myocardium that receives coronary circulation, which supplies oxygenated blood directly from gills to the heart. A spongy heart receives oxygen only from the venous deoxygenated blood within its chambers, which is a less reliable oxygen source during exercise, stress and hypoxia. Across all the teleost species, a coronary circulation is present mainly in highly athletic and hypoxia-tolerant species. Air-breathing fishes may have evolved a different way to better secure a reliable oxygen supply to its myocardium.