Question

Which one of the following is a true fish?
A. Jellyfish
B. Starfish
C. Dogfish
D. Silverfish

Answer 1

Hint: True fishes are the fishes that belong to phylum chordate and Pisces is the super class under the class tetrapoda. Vertebrae, gills for movement, scales on body, swim bladders are some general characteristics of being a true fish.

Complete answer:
> Option A is incorrect because the jellyfish belongs to the phylum cnidaria and belongs to predominant non-poly species. Jellyfish are not considered as a jellyfish as jellyfish do not fit into the fish family as fins, vertebrae, and gills are some basic characteristics of being a fish. Therefore, jellyfish are not considered as true fish.

> Option B is incorrect – Silverfishes are not a true fish because starfish is a member of the phylum Echinodermata. Silverfishes live in saltwater and resemble the fishes, but they do not have gills, scales, or fins. Sea stars mostly live underwater.

> Option C is incorrect because the dogfish belongs to the class Chondrichthyes of super class, Pisces. It is also known by the name scoliodon. It is the true fish that belong to the phylum chordata.

> Option D is incorrect as silverfish is also known as Lepisma saccharina belongs to the phylum arthropoda and order of lepisma or thysanura. They are small primitive insects that look similar in appearance to fishes. Their bodies do not possess’ gills that are one of the prime characteristics of being fishes.

Hence, the correct answer is option (C).

Additional information:
During the embryonic development, fishes have notochord that after development becomes backbone. Fishes do not maintain their body temperature by themselves and are influenced by the surroundings temperatures. Fins are of long winged types and help them for gliding purpose.

Note: Unlike mammals fish are cold-blooded in nature comes under ectodermic category. Jellyfish and starfish did not have gills, fins and vertebral columns. Silverfish is a type of aquatic insect that resides in water and looks like a fish.