Learn about the comparison between the respiratory system of elasmobranch and teleost.
Comparison # Respiratory System of Elasmobranch:
1. In the wall of the pharynx there are five pairs of gill clefts separated by complete partitions. The partition wall between the two clefts is known as intrabranchial septum.
2. Gills of Elasmobranch are lamelliform.
3. The intrabranchial septa are supported by the branchial and hyoid arches with their rays. The first cleft is bounded anteriorly by the hyoid arch and posteriorly by the first branchial arch.
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4. The first four gill slits are bounded by gill filaments on both anterior and posterior margins while in the fifth, filaments are present only on its anterior margin. Each set of branchial filament is known as half-gill or hemi- branch and the first four gills slits are bounded by a half-gill on each side and the fifth by only a half on its anterior surface.
5. A minute aperture or spiracle opens dorsally behind the eye on each side, and contains a rudimentary gill (pseudobranch) on the anterior wall supported by a spiracular cartilage in Scylorhinus, while in Scoliodon it bears no gill lamellae. Through the spiracle water enters the mouth when the animal is at rest.
6. Gill chamber and operculum are absent in Elasmobranch.
7. The gills are richly supplied with blood from the afferent branchial system and gaseous exchange takes place there.
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Mechanism of respiration:
During respiration, the floor of the mouth is lowered and the pharynx is expanded. Due to increased space thus created, water rushes in through the open mouth. Now the mouth is closed, the buccal floor is raised, the pharyngeal wall contracted and the water is forced out through the gill slits.
A repetition of this process maintains a continuous water current through the gill slits which carries dissolved O2 and food particles with it.
Comparison # Respiratory System of Teleost:
1. In the wall of the pharynx there are five pairs of gill clefts separated by thickened stripes. The partition between the two clefts is reduced to a branchial arch.
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2. Gills of Teleost are filliform or pectinate.
3. The branchial arches are supported by bony structures. Between the five slits on each side there are four branchial arches.
4. Each branchial arch bears externally on its convex margin two rows of gill filaments. One row is borne on the anterior border and the other on the posterior border of each branchial arch. Such a gill, bearing a double set of branchial filaments is known as holo- branch. The inner margins of the branchial arches are provided with horny gill rakers.
On the internal surface of the operculum lies a red patch, the pseudobranch or rudimentary hyoideal gill.
6. All the gills of each side are placed in a chamber known as gill chamber. The gill chamber is covered externally by a bony structure, the operculum, at the posterior margin of which is a thin branchiostegal membrane.
7. The gills of Teleost are richly supplied with blood from the afferent branchial system and gaseous exchange takes place there.
Mechanism of respiration:
During respiration, the branchiostegal membranes are pressed against the body wall. The floor of the mouth is lowered and the pharynx is expanded. Due to increased space thus created water rushes in through the open mouth.
Now the mouth is closed, the buccal floor is raised, the pharyngeal wall contracted, the opercula raised, branchiostegal membranes released and the water is forced out through the gill slits to the branchial chamber and from there to the exterior. A repetition of this process maintains a continuous water current through the gill slits which carries dissolved O2 and food particles with it.