Table of Contents
Scoliodon, commonly known as dogfish, is a genus belonging to the requiem sharks in the family Carcharhinidae. Two species of the genus are known: Scoliodon laticaudus and Scoliodon macrorhynchos. They are commonly found in the Indo-West Pacific oceans in the west coasts of Africa and Japan.
Classification
Kingdom |
Animalia |
Phylum |
Chordata |
Class |
Chondrichthyes |
Order |
Carcharhiniformes |
Family |
Carcharhinidae |
Genus |
Scoliodon |
Components of the Circulatory System
Blood
Blood of the dogfish is composed of colourless plasma with blood cells suspended in it. Two types of blood cells are found: RBC and WBC. The RBCs are oval bodies that contain a nucleus whereas WBCs are amoeboid in shape.
Heart
The heart of Scoliodon is situated ventrally beneath the pharynx in the head region. It consists of four chambers: sinus venosus, atrium, ventricle and conus arteriosus.
Receiving Parts of the Heart
The sinus venosus and the atrium make up the receiving part of the heart. The sinus venosus is a thin-walled tubular chamber from where the heartbeat originates. The duct of Cuvier opens into the sinus venosus laterally on both the sides.
Posteriorly, two hepatic sinuses open into the sinus venosus. The sinus venosus opens into the auricle by a sinu-auricular aperture that is guarded by two valves in pairs.
The auricle is a large, thin-walled, triangular chamber that is situated in front of the sinus venosus and dorsally to the ventricle. The auricle is connected to the ventricle by an auriculoventricular aperture that is guarded by two valves. The receiving part of the heart receives venous blood from all body parts.
Forwarding Parts of the Heart
The conus arteriosus and the ventricle make up the forwarding part of the heart. The ventricle is an oval-shaped, thick-walled muscular structure that has muscular strands on its inner surface giving it a spongy texture. It is the most prominent part of the heart.
The conus arteriosus is a tube-like structure arising from the ventricles. The lumen of the conus arteriosus has semilunar valves that are attached to the ventricular walls by chordae tendineae. The conus arteriosus continues forward as ventral aorta.
The heart functions to receive deoxygenated blood from all body parts and pump it to provide aeration for gills. This type of heart is known as venous heart.
Arterial System
The arterial system of Scoliodon is divided into two categories:
- Afferent branchial arteries: These arteries arise from the ventral aorta which supply deoxygenated blood to the gills for oxygenation.
- Efferent branchial arteries: These arteries arise from the gills and supply oxygenated blood to all body parts.
Venous System
Deoxygenated blood from all body parts is returned to the heart by the means of veins. The veins form irregular blood sinuses throughout the pathway. The presence of these blood sinuses is an exclusive feature of the Scoliodon.
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