Question

In which of the following groups the operculum is present?
A. Polypterus
B. Hippocampus
C. Holocephali
D. Teleostomi
E. Both C and D

Answer 1

Hint: The fishes on the basis of their structures and composition of the skeleton is divided into cartilaginous fishes and bony fishes. The cartilaginous fishes possess gill slits and gills open directly to the exterior. In bony fishes, operculum is a series of bony structures that covers the gills. It is used for respiration and feeding.

Complete step by step answer: Bony fishes contain a series of four bones known as the opercular series. The four bone segments are pre-operculum, sub- operculum, inter- operculum and operculum. The pre- operculum contains a series of ridges that are directed to the organisms’ canal pores. It is directed posterodorsal. The pre- operculum is a crescent shaped structure. It is located through an exposed condyle. The condyle is present immediately under the ventral margin. The pre- operculum marks the border of operculum, sub- operculum and inter - operculum.
The sub- operculum is rectangular in shape and is present ventral to the pre- operculum and operculum components. it is located directly above the gills. It is the thinnest bone segment out of the four components. The inter – operculum borders the sub- operculum in the posterodorsal position and pre- operculum in the anterodorsal position. The inter- operculum is the shortest bone. It is present on the dorsal and ventral surrounding borders.
Polypterus is a freshwater fish belonging to the order Polypteriformes. It is the only known vertebrate to possess lungs but no trachea. It bears spiracles.
Hippocampus is commonly known as sea- horse. They belong to the family of ray-finned fishes.
Holocephali belongs to the cartilaginous fishes and are highly specialized marine fish. They are known to possess gill slits and not operculum.
Teleostomi fishes include an operculum and single pair of respiratory openings. The operculum was however not similar to the recent fishes.
Therefore, the correct option is option D.

Note: In bony fishes, operculum serves as a vital organ in obtaining oxygen. As the fishes open the mouth, the pressure inside the fishes drops and water then flows across the fishes, gill lamina which allows oxygen to be absorbed by gills. Operculum helps to provide a continuous flow of water over the gills