The heart of ruhi fish is located in the pericardial cavity. It is covered by the pericardium. It is called a myogenic heart because the heart muscle in the heart wall produces the heartbeat. The parts of the heart are:
1. Subchamber or sinus venosus: Sinus venosus is a triangular shaped and elastic subchamber. It is thin walled. Blood enters the sinus venosus from the veins, ductus cuveae, and hepatic sinuses. Blood enters the atrium from the sinus venosus. Siddique Publications
2. Atrium: The atrium is the largest chamber of the heart. It is triangular, muscular and thin walled. One end is connected to the ventricles and the other end to the sinus venosus. It collects blood containing CO2 from the sinus venosus and delivers it to the lungs. Siddique Publications
3. Ventricle : Ventricle is a muscular, fleshy and thick walled cavity. One end of the ventricle is connected to the atrium and the other end to the bulbus arteriosus. It is filled with blood containing CO2. Dr. Siddiq Publications
4. Bulbus arteriosus: Conus arteriosus is absent in the heart of roe fish. The root of the artery swells to form the bulbus arteriosus. The bulbus arteriosus is not part of the heart as it is not covered by myocardium or pericardium. It delivers blood from the heart to the ventral aorta. Dr. Siddiq Publications
5. Cardiac valves: There are three types of valves in the heart of roe fish.
(i) Sino-atrial cavity: It lies between the sinus venosus and the atrium.
(ii) Atrio-ventricular chamber: It lies between the atria and the ventricles.
(iii) Ventriculo-bulbus capatica: It lies between the ventricles and the bulbous aorta.