Question

What Is The Main Difference Between Placoid And Ctenoid Scales?

Answer 1

• Scales are rigid structure that grow out on the skin of fishes.
• Scales are an important characteristic for most fish. For instance, scales provide protection against predators.
• They also provide camouflage through reflection and colouration, which makes fishes harder to spot.
• There are 4 types of scales of fishes:

1. Placoid.
2. Cycloid and Ctenoid.
3. Cosmoid
4. Ganoid

• Placoid Scales: These scales are spiny, toothlike structures found only in cartilaginous fishes like sharks, rays and skates.
• Ctenoid Scales: These scales have comb-like tooth along their free edges and are found only in bony fishes like sunfish, catfish and trouts.

Placoid scales are predominantly found in cartilaginous fish while ctenoid scales are more common in bony fish.