Question

A marine bony fish continuously
A. Acquire water and get rid of salt
B. Get rid of both water and salt
C. Get rid of water and acquire salt
D. Acquire both water and salt

Answer 1

Hint:Bony fishes are also referred to as Osteichthyes. They are cold-blooded vertebrates that use fins for swimming and gills for respiration. Bony fishes are present in both marine and freshwater environments. Their body shape is also vast which includes small fishes like Philippine goby and large fishes like swordfishes.

Complete answer:
Acquire water and get rid of salt- The internal osmotic concentration of marine bony fishes is lower than the surrounding seawater, so it tends to get rid of salt and acquire water. Marine fishes lose a lot of water through osmosis to their surroundings. To compensate they have to drink a lot of water and secrete excessive salt from their gills to the surrounding seawater.
Get rid of both water and salt- Although marine fishes get rid of excess salt they cannot get rid of water.
Get rid of water and acquire salt- Since the internal osmotic concentration of bony fish is low therefore it has to take up water from surroundings and cannot get rid of water. The salt is removed from the body due to the process of osmosis. Since there is more salt in the body than in the surrounding water, it has to be secreted out and therefore the bony fishes cannot acquire salt.
Acquire both water and salt- The marine bony fishes cannot acquire both water and salt. It acquires only water.

Therefore the correct answer is (A) Acquire water and get rid of salt.

Note:
 Body fluids of marine fishes are hypotonic to seawater therefore there is a loss of water from the gill membrane, oral membrane, and anal membrane. Marine bony fishes thus conserve water through osmosis. But the cartilaginous fishes such as sharks have an efficient mechanism to conserve water different from the bony fishes i.e. osmoregulation. Such fishes have a rectal gland that secretes the excess salt present in the body.