Question

The circulation of blood in fishes is called.
A. Venous circulation
B. Double circulation
C. Arterial circulation
D. Arterial and venous circulation

Answer 1

Hint: Fishes are aquatic organisms. They oxygenate blood through gills via respiration. The heart of fishes has only two chambers. Single circulation is present in fishes.

Complete answer: Fishes have a single type of circulation. The heart of a fish has only one atrium and one ventricle. Fishes have two-chambered hearts. The heart of a fish collects blood from veins for pumping it to the gills for oxygenation.
a) Venous circulation: In this type of circulation, blood flows through veins into the heart and then goes to the gills. The oxygenated blood flows into other parts of the body from gills. The deoxygenated blood that returns from the body goes to the atrium and then into the ventricle. This is how the blood circulation is carried out in fishes.
b) Double Circulation: In this type of circulation, the blood flows two times through the heart. This type of circulation is usually found in the organisms which have four-chambered hearts for example humans. Four chambered heart has two auricles of atria and two ventricles. In humans, the right side of the heart receives deoxygenated blood and the left side receives oxygenated blood.
In fishes, the deoxygenated blood flows once through the heart which is called single circulation. Only venous blood flows through the heart in fishes. So it is known as venous circulation.
Hence, the correct answer is option A.

Note: In humans, coronary venous flow occurs during diastole and systole, and the coronary venous system drains the myocardium of oxygen-depleted blood. It dominates the arterial system of the body.