What are pisces? Classify and explain two different kinds of fishes by the help of suitable examples.
Solution
Pisces is a super class of subphylum Gnathostomata, which consists of following two classes:
Class 1: Chondrichthyes
(a) Marine fishes with entirely cartilaginous endoskeleton.
(b) They have a streamlined body that is either compressed laterally or flattened dorsoventrally.
(c) Mouth is ventral in position.
(d) Skin is tough and covered with minute placoid scales.
(e) Respiration occurs via gills.
Examples: Scoliodon and Torpedo
Class 2: Osteichthyes:
(a) Marine and fresh-water fish with partial or full bony endoskeleton.
(b) Their size varies from 10 mm to 4 metres.
(c) They have a spindle-shaped body.
(d) Four pairs of gills are present for respiration.
(e) They excrete ammonia (ammonotelic animals).
Examples: Labeo and Protopterus.
