What are pisces? Classify and explain two different kinds of fishes by the help of suitable examples.

Pisces: These are fish. They are exclusively waterliving animals. Their skin is covered with scales. Pisces are cold-blooded animals and have two-chamered heart. They obtain oxygen dissolved in water by using gills. The body is streamlined, and a muscular tail is used for movement.

Superclass Pisces is classified into two classes:

(i) Chondrichthyes – The cartilaginous fishes

(ii) Osteichthyes – The bony fishes

(i) Chondrichthyes – The cartilaginous fishes

(Gr; chondros = cartilage + ichthys = fish)

● They are marine animals with streamlined body and have cartilaginous endoskeleton.

● The skin is covered with minute placoid scales.

● Mouth is located ventrally.

● Notochord is persistent throughout life.

● Gill slits are separate and without operculum (gill cover).

● Air bladder is absent.

● Sexes are separate.

● Examples- Scoliodon (Dog fish), Pristis (Saw fish), Torpedo (electric ray), Trygon (Sting ray).

(ii) Osteichthyes – The bony fishes

(Gr; osteon=bone + ichthyes=fish)

● It includes both marine and fresh water fishes with bony endoskeleton.

● Skin is covered with cycloid/ctenoid scales.

● Mouth is located mostly terminal.

● They have four pairs of gills which are covered by an operculum on each side

● Air bladder is present which regulates buoyancy.

● Sexes are separate.

● Examples-Exocoetus (Flying fish), Hippocampus (Sea horse); Labeo (Rohu), Catla (Katla), Clarias (Magur).