Question

A cartilaginous fish with an operculum is:
A. Scoliodon
B. Chimaera
C. Torpedo
D. Trygon

Answer 1

Hint: The operculum is a group of bones found in bony fish which provides protective covering for the gills and it is also used for respiration and feeding. The operculum is composed of corneous protein material, which is yellow to brownish in colour.

Complete answer:
Scoliodon, chimaera, torpedo, trygon fall under the class Chondrichthyes and subclass Pisces.
Characteristics of Chondrichthyes:
> They are marine animals with streamlined bodies.
> Endoskeleton made up of cartilage.
> Teeth are modified placoid scales.
> Kidneys are mesonephric.
> Heart is two chambered.
> Fertilization is internal.
> Sexes are separate and show sexual dimorphism.
> In males pelvic fins bear claspers which are used in copulation.
> Air bladder is absent.
> Gill slits are separate and absence of operculum (gill cover). Chimaera are the only exception in which operculum is present.
Scoliodon: It is commonly called dogfish. Scoliodon is carnivorous and surface eater. Numerous dermal placoid scales are present on the skin. This fish is also eaten as food by some people and it yields liver oil.
Torpedo: It is commonly called an electric ray. It is also carnivorous and kills the prey and enemies with electric shock from its electric organs. Electric discharge varies from 8 volts to 220 volts.
Trygon: It is commonly called stingray. It is a bottom dwelling, carnivorous fish.
Chimaera: It is commonly called rat fish, ghost fish or king of Herrings (small silver fish). It bears a cartilaginous skeleton and a pair of pelvic claspers (characters of shark and bony fish). Cloaca is absent and it possesses operculum on each side.

So the correct answer is option B.

Note: The great white shark (Carcharodon) is ranked first in a list which shows the highest number of attacks on humans. Sharks are viviparous and ureotelic in nature.