Question

In fishes, hypocalcin is secreted by

• A. Thyroid gland
• B. Ultimobranchial bodies
• C. Pancreas
• D. Corpuscles of Stannius

Hint:

Corpuscles of Stannius are unique to bony fishes.
Their major secretion is Stanniocalcin (Hypocalcin), which prevents calcium levels from rising too high.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Endocrine regulation of calcium levels in teleost fishes is controlled by specialized hormones that either raise (hypercalcemic) or lower (hypocalcemic) plasma calcium.

Step 2: Detailed Explanation:
Let us analyze the calcium-regulating glands in fishes:
The thyroid gland regulates metabolism and growth via thyroxine.
The Ultimobranchial bodies secrete calcitonin, which has a weak hypocalcemic effect in fishes.
The pancreas regulates blood glucose levels via insulin and glucagon.
The Corpuscles of Stannius are unique endocrine glands found exclusively in teleost and holostean fishes, typically embedded in or attached to the kidneys.
These glands secrete a primary protein hormone known as hypocalcin (historically also called stanniocalcin).
Hypocalcin is a powerful hypocalcemic hormone.
It prevents hypercalcemia by directly inhibiting calcium uptake across the fish gills from the surrounding water, and promoting calcium excretion.
Therefore, hypocalcin is secreted by the Corpuscles of Stannius.

Step 3: Final Answer:
Hypocalcin is secreted by the Corpuscles of Stannius.