Question

A marine cartilaginous fish that can produce electric current is:
A) Pristis
B) Torpedo
C) Trygon
D) Scoliodon

Answer 1

Hint: Cartilaginous fish are fish that have a skeleton made of cartilage, rather than bone. All sharks, skates, and rays are cartilaginous fish. These all types of fish fall into the group of fish, which is called the elasmobranchs. Cartilaginous fish have gills that open to the ocean by slits.

Complete answer: 

> Torpedo is a marine cartilaginous fish, which produces an 8-220 volt electric charge or current depending on some species. It is a kind of bottom-living marine fish, discharging electricity which is sufficient to stun prey like small fishes, etc. A pair of electric organs are located on the dorsal side of the trunk region. Their electric organs are changed lateral muscle plates innervated by cranial nerves. Trygon (Stingray) looks like an electric ray in many aspects but is devoid of electricity discharging (or producing) organs.
> Scoliodon is also called dogfish. It is known for its great sense of smell. Pristis or common sawfish is characterized by a long, narrow, flattened rostrum lined with sharp transverse teeth to resemble a saw.

Hence, the correct answer is Option (B).

Additional information:
Chondrichthyes characteristics are listed below:
• They are generally marine fishes.
• They possess a pair of jaws. Their jaws are very much powerful.
• The mouth is present ventrally.
• They possess a cartilaginous endoskeleton, the deposits of calcium salts provide strength to it.
• The notochord is present throughout their life.
• Most of them possess a heterocercal tail. The tail contains two lobes, the upper lobe is elongated and the vertebrae extend into it and a shorter lower lobe, giving rise to the distinct heterocercal tail.
• The skin is covered by minute tooth-like structures called placoid scales.

Note: Some important points:
• Cartilaginous fishes fall under the class Chondrichthyes.
• They have skeletons composed primarily of cartilage.
• Tails are heterocercal in nature.
• Swim bladder is absent. Buoyancy is maintained with oil stored in livers.