Question

The marine fish among the following varieties is
(a) Stromateus
(b) Labeo
(c) Cirrhina
(d) Catla

Answer 1

Hint: A fish is of two types based on the nature of the endoskeleton. The marine fish among the following varieties is a fish with a bony endoskeleton. It is commonly known as Blue butterfish and possesses a flattened body with a lot of colors.

Complete answer:
Bony fishes or Osteichthyes are aquatic vertebrates who possess bony endoskeleton in the adult form. The endoskeleton is cartilaginous in the embryonic stage. They are ectothermic i.e. cold-blooded and more than 25,000 species exist. Bony fishes occur in all sorts of waters – freshwater, marine, brackish. Stromateus is an example of marine bony fish.

Additional Information:
-The blood and tissue fluids of marine bony fishes are hypotonic to the surrounding medium. This poses a threat of water loss from the body of fishes into the environment by osmosis. In such circumstances, the marine bony fishes are adapted to take large amounts of water into the gut and reduce the production of urine. Also, excess salt which has entered the body is excreted from the gills and kidneys.
-In freshwater bony fishes like Labeo, Catla, Cirrhina the blood and tissue fluids are hypertonic to the surrounding medium and thus water is constantly flushed inside by osmosis. To balance this, kidneys excrete hypotonic urine i.e excess of water is secreted out from the body into the environment.

So, the correct answer is ‘ Stromateus.’

Note: Bony fishes are ammonotelic i.e they secrete ammonia as the main excretory product. Nitrogenous waste substances such as urea, ammonia, and uric acid are produced during protein or nucleic acid metabolism. Ammonia is the most toxic of all which is followed by urea and uric acid. Ammonia required a large amount of water to be excreted out from the body and thus is the main excretory product of most aquatic animals.