Question
Distinguish between Chondrichthyes and Osteichthyes.
| Chondrichthyes | Osteichthyes |
| 1. Endoskeleton is made of cartilage. | Endoskeleton is made of bones. |
| 2. Exoskeleton is made of minute scales called placoid scales. | Exoskeleton is made of large, flat and overlapping cycloid or ctenoid scales. |
| 3. Mouth is ventral in position. | Mouth is mostly terminal in position. |
| 4. 5-7 pairs of gill slits without operculum are present. | Four pairs of gills covered by operculum are present. |
| 5. Caudal fin is heterocercal. | Caudal fin is homocercal. |
| 6. Males have copulatory organs called claspers located between the pelvic fins. | Males lack claspers. |
| 7. Air bladder is absent. | Air bladder is present to maintain buoyancy. Thus, these fishes do not need to swim constantly. |
| 8. Fertilization is internal. | Fertilization is external. |
| 9. Many of them are viviparous animals. | They are oviparous animal |
| 10. Scolidon (Dogfish), Pristis (Sawfish), Electric ray, Common skate, Hammer headed shark, Carcharodon (Great white shark), Trygon (Stingray), Anoxypristis. | Exocoetus (Flying fish), Hippocampus (Sea horse), Labeo rohita, Pomphret (Rohu), Catla (Katla), Clarius (Magur), Pterophyllum (Angle fish), Bombay duck, Lung fishes (Protopterus, Lepidosireri), Aquarium fishes like Betta (Fighting fish). |
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