Question

Which one has a heterocercal tail?
A. Dipnoi
B. Bony fish
C. Cartilaginous fish
D. All of the above

Answer 1

Hint: The tail of shark is heterocercal as its upper lobe is larger than the lower lobe. In the homocercal tail the both lobes are the same.

Complete Answer:
- The heterocercal tail is a caudal fin consisting of two asymmetric lobes. Sometimes, as in many sharks, the spinal column moves through the upper lobe, making it the larger of the two lobes.
- The heterocercal tail is compared with the homocercal tail, which has the same lobes. The homocercal tail is a caudal fin made up of two lobes of similar proportion. Homocercal tails are the most common type of caudal fin fish, but they can come in several symmetrical shapes.
- Dipnoi are a group of sarcopterygian fish, commonly known as lungfish. Their "lung" is a modified swim bladder that is used for swimming in most fish, but also absorbs oxygen in the lungfish and eliminates waste. They are bony fish that have a homocercal tail.
- The skeleton of bony fishes is composed of bones instead of cartilage. Bony fishes have homocercal tails which are made up of two lobes of similar proportion.
- Cartilaginous fish are jawed vertebrates with paired fins, scales, and cartilaginous skeleton rather than bone. They have a heterocercal tail which consists of two asymmetric lobes.

Thus, the correct answer is option C. i.e., Cartilaginous fish.

Note: The primary purpose of the tail is to move enough water for each stroke or rhythm, which allows the fish to move forward. The actual forward thrust is created by the pressure that the moving tail produces as it pushes against the surrounding water.