Question

Name the class of fish where the tail fin is heterocoel.

Answer 1

Hint: Heterocoel is a type of tail of a fish in which the upper lobe is comparatively larger than the lower lobe. It is a caudal fin. The heterocercal fin is a type of fin in which the tip of the vertebral column turns upwards and stretches up to the dorsal lobe of the tail fin.

Complete answer:
The class of the fish in which the tail is heterocoel is Chondrichthyes. This type of tail is found in the cartilaginous fishes and that are usually marine. In the younger fishes notochord is present but after maturity, the notochord is converted into cartilage. They have a streamlined body with a cartilaginous exoskeleton. The gill slits are divided and without operculum which is a cover of the gills. The skin is tough and is covered with minute placoid scales. Their jaws are very powerful and they are predaceous. They possess a two-chambered heart.
They do not have an air bladder and as a result, they have to swim constantly to avoid sinking. The heterocercal tail fin is found in the shark fish and they help them to swim steadily in the water and it is unequal. They are the cold-blooded animals, they do not have the power to regulate their body temperature.

Note: The rays of the fin are soft and they are unsegmented. They possess the liver filled with lipids or oils which gives them neutral buoyancy for swimming.