Question

List out the differences between class-Chondrichthyes and class Osteichthyes.

Answer 1

• Chondrichthyes
  

1. The mouth is ventral in position.
2. The body is covered with minute and microscopic placoid scales, the skin is tough.
3. Paired pelvic fins are provided with claspers in males.
4. The tail is heterocercal, the vertebral column extending into the dorsal part of the caudal fin.
5. The head is dorsoventrally flattened.
6. Gill slits, usually five pairs, open sepa­rately and directly to the exterior.
7. The gills are hemibranch/holobranch.
8. Operculum always absent.
9. A spiracle usually present.
10. The endoskeleton is cartilaginous.

• Osteichthyes

1. The mouth is apical in position.
2. The body is covered with cycloid or ctenoid or ganoid scales.
3. The skin is soft. Complete absence of scales in cat fish group.
4. Claspers are absent.
5. The tail is homocercal, the vertebral column ends at the middle of the base of the caudal fin.
6. The head may be dorsoventrally or laterally flattened.
7. Gill slits, usually four pairs, open in a gill chamber.
8. The gills are holobranch.
9. Operculum with branchiostegal mem­brane always present.
   
10. A spiracle is absent.The endoskeleton is bony with amphicoelous vertebrae.