A fresh water fish maintains osmoregulation by

Options

A. Continuously taking in water and eliminating excess of salts
B. Eliminating excess of water and taking up salts from the environment
C. Taking both water and salt from the environment
D. Eliminating both salt and water into the environment

Answer

### Step-by-Step Solution:

1. **Understanding Osmoregulation**:
- Osmoregulation refers to the process by which organisms maintain the balance of water and salts in their bodies, ensuring that their internal environment remains stable despite external changes.

2. **Freshwater Fish Environment**:
- Freshwater fish live in a hypotonic environment, meaning the concentration of salts (solutes) in the surrounding water is lower than that inside their bodies. This creates a tendency for water to enter the fish's body through osmosis.

3. **Salt and Water Balance**:
- Since freshwater fish have a higher concentration of salts in their bodies compared to the surrounding water, they must actively manage the influx of water and the loss of salts to maintain homeostasis.

4. **Mechanisms of Osmoregulation**:
- Freshwater fish continuously take in water through their skin and gills.
- They have specialized cells in their gills that help in the excretion of excess salts. These cells actively transport salts out of the fish's body into the surrounding water.

5. **Kidney Function**:
- The kidneys of freshwater fish are adapted to excrete large volumes of dilute urine. This helps in the removal of excess water while reabsorbing necessary salts back into the body.

6. **Conclusion**:
- Based on the mechanisms described, the correct answer to how freshwater fish maintain osmoregulation is: **"continuously taking in water and eliminating excess of salt."**