Physiology of Finfish and Shellfish (2+1)

2.2.6. Cyclostomes

Hag fish

The circularly system of hag fish differs from that of all other vertibrates. It is party are open system with large head sinus, rather than a closed system as in other vertibrates. In addition to the regular hear (the branchial heart) the hag fish has several accessory hearts. There are three sets of such accessory hearts, the portal heart.

1. Portal heart: Receives venues blood from the cardinal vein and from the intestine and pumps blood to the liver.
2. Pumps blood to the liver.
3. Cardinal hearts: Paird expansions of the candal veins → help to propel the blood.
4. Candal hearts: Paird expansion of the candal veins.

Shark

The heart consists of two chambers in series, on atrium and a vontride. Sinus venosus which helps assure a continous flow of blood to the heart. On the arterial side the letcost heart is immediately followed by a there muscular part of the ventral aorta the bulbus arleriosus. The clasurobranch heart has a similarly located thickend part the cones arteriosus. It is fibrous and is equated with valves that prevent back flow of blood into the ventricle.

Lung fish

The major evolutionary change in lung fish is that, in addition to gills, they have lungs as respiratory organs. The atrium of the heart is divided into two chambers by a septum and the ventricle is partially divided. In this way the lungfish heart somewhat resembles the completely divided heart of mammals birds and crocodiles.

The caudal hearts of the hag fishes are particularly interesting because they differ in design from all other hearts. a longitudinal rod of cartilage separates two chambers and alternate contractions of muscles on the two sides cause the rod to be flexed.

As the muscles on one side contract, those on the opposite side provide preserve for expulsion of the blood on that side.

The major evolutionary change in lung fish is that, in addition to gills, they have lungs as respiratory organs. The atrium of the heart is divided into two chambers by a septum and the ventricle is partially divided. Blood from the lungs returns to the left atrium and the right atrium receivers blood from the general circulation studies of live African lung fish (Protopteres) show that circulation to the systemic vascular circulation have a high degree of functional separation, with preferential passage of oxygen poor blood to lungs and oxygen rich blood to the systematic circulation.