The hormone involved in the regulation of osmoregulation is:

Correct option is C

Correct Answer: (c) Prolactin
Explanation:
→ Prolactin is the major hormone controlling freshwater osmoregulation in fishes.
→ It helps maintain ionic balance by reducing ion loss and increasing water excretion.
→ Essential for fishes transitioning from saltwater to freshwater.
Information Booster:
→ Prolactin acts on gills, kidney, and intestine to increase ion uptake.
→ Works opposite to cortisol, which supports seawater adaptation.
→ Crucial for survival during salinity stress.
Additional Information (Other Options):
(a) Cortisol: Promotes seawater adaptation.
(b) Catecholamine: Emergency response.
(d) Corticotropin: Stimulates cortisol but not osmoregulation directly.