Question

Chondrichthyes can be differentiated from osteichthyes externally by

• A. Naked gills
• B. Heterocercal tail
• C. Number of chambers in heart
• D. Ventral mouth

Answer 1

Answer: (A), (B), (D)

Ventral mouth

Cartilaginous fishes (Chondrichthyes) possess naked gills (no operculum), while bony fishes (Osteichthyes) have gills covered with operculum. Chondrichthyes mostly have a heterocercal tail, that is, both the lobes of the tail are not similar in size; the dorsal lobe is often larger than the ventral lobe. Osteichthyes typically have a homocercal fin, in which the tail lobes externally appear symmetrical. This happens as a result of the differences in internal skeletal structures. Cartilaginous fishes have a ventral mouth, while bony fishes have a terminal mouth. The number of chambers in the heart is two in all fishes.