Question

These are dermal scales of fish. Match them with their names and choose the correct option from the following.
(i) Placoid, (ii) Cycloid, (iii) Ctenoid, (iv) Ganoid

• A. (i)- B, (ii)- D, (iii)- C, (iv)- A
• B. (i)- C, (ii)- B, (iii)- D, (iv)- A
• C. (i)- A, (ii)- B, (iii)- C, (iv)- D
• D. (i)- D, (ii)- B, (iii)- C, (iv)- A
  

Answer 1

The correct option is D

(i)- D, (ii)- B, (iii)- C, (iv)- A

Placoid scales are tooth-like, being made of dentine with a pointed backward projection of enamel, as in sharks and rays.

Cycloid (circular) scales have a smooth texture and are uniform with a smooth outer edge or margin. They are most common on fish with soft fin rays, such as salmon and carp.

Ctenoid (toothed) scales are like cycloid scales with small teeth along their outer edges and are usually found on fish with spiny fin rays, such as the perch-like fishes. They have a rough texture with a toothed outer or posterior edge with tiny teeth called as ctenii.

Ganoid scales are found in the sturgeons, gars, bowfin. They are derived from cosmoid scales, with a layer of dentine in the place of cosmine and a layer of inorganic bone salt called as ganoine in place of vitrodentine. Most are diamond-shaped and connected by peg and socket joints.

So, the correct answer is '(i)- D, (ii)- B, (iii)- C, (iv)- A'