Animal Kingdom - Notes | Class 11 | Part 13: Chordata (Cyclostomata, Pisces)

4. ANIMAL KINGDOM

CLASS CYCLOSTOMATA

• All are ectoparasites on some fishes.
• Elongated body without scales and paired fins.
• 6-15 pairs of gill slits for respiration.
• Sucking and circular mouth without jaws.
• Cartilaginous cranium and vertebral column.
• Circulation is closed type.
• Marine, but migrate for spawning to fresh water. After spawning, they die. Their larvae, after metamorphosis, return to ocean.
• E.g. Petromyzon (Lamprey) and Myxine (Hagfish).

SUPERCLASS PISCES (FISHES)

Class Chondricthyes (Cartilaginous fishes)

• Marine. Stream-lined body. Predaceous.

• Cartilaginous endoskeleton.

• Notochord is persistent throughout life.

• Ventral mouth.

• Gill slits without operculum. Powerful jaws.

• Skin with placoid scales. Teeth are modified placoid scales which are backwardly directed.

• No air bladder. So, they have to swim constantly to avoid sinking.

• Poikilotherms (Cold-blooded animals): Animals that lack the capacity to regulate their body temperature.

• Two-chambered heart (one auricle and one ventricle).

• Sexes are separate. In males, pelvic fins bear claspers. Internal fertilization. Many of them viviparous.

    Examples

• Scoliodon (Dogfish)

• Pristis (Saw fish)

• Carcharodon (Great white shark)

• Trygon (Sting ray- has poison sting)

• Torpedo (Electric ray- has electric organ).

Class Osteichthyes (Bony fishes)

• Marine & fresh water. Stream-lined body.

• Bony endoskeleton.

• Terminal mouth.

• 4 pairs of gills covered by operculum on each side.

• Scales are Cycloid, ctenoid etc.

• Air bladder for buoyancy.

• Poikilotherms (cold-blooded).

• Two-chambered heart (one auricle and one ventricle).

• Sexes are separate. External fertilisation.

• Mostly oviparous. Development is direct.

    Examples:

• Marine: Exocoetus (flying fish), Hippocampus (seahorse)

• Fresh water: Labeo (Rohu), Catla (Katla), Clarias (Magur).

• Aquarium: Betta (Fighting fish), Pterophyllum (Angel fish).

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👇 Select Your Topic Here 👇

• Topic 1: Basis of Classification
• Topic 2: Porifera
• Topic 3: Cnidaria
• Topic 4: Ctenophora
• Topic 5: Platyhelminthes
• Topic 6: Aschelminthes
• Topic 7: Annelida
• Topic 8: Arthropoda
• Topic 9: Mollusca
• Topic 10: Echinodermata
• Topic 11: Hemichordata
• Topic 12: Chordata - up to Sub phylum Vertebrata
• Topic 13: Chordata - Cyclostomata, Pisces
• Topic 14: Chordata - Tetrapoda