which of the following statements is correct w.r.t. osmoregulation in Marine environment?

Options

A. entry of excess water in body followed by removal of large quantities of urine
B. optic of monovalent and divalent ions by ionocytes actively
C. loss of water from the body replenished by drinking sea water and eliminating monovalent ions actively
D. loss of divalent ions are actively through ionocytes

Answer

To solve the question regarding osmoregulation in the marine environment, we will analyze the statements provided and determine which one is correct based on our understanding of osmoregulation in marine organisms, particularly marine fish.

### Step-by-Step Solution:

1. **Understanding Osmoregulation**:
- Osmoregulation is the process by which organisms regulate the balance of water and salts in their bodies to maintain homeostasis. In marine environments, this process is crucial due to the high salt concentration in seawater.

**Hint**: Remember that osmoregulation involves balancing water and salt levels in the body.

2. **Marine Environment Characteristics**:
- Marine fish live in a hypertonic environment (the sea), meaning the concentration of salt in the seawater is higher than that in their bodies. Consequently, water tends to move out of the fish into the seawater.

**Hint**: Identify the difference between hypotonic (lower salt concentration) and hypertonic (higher salt concentration) environments.

3. **Water Loss in Marine Fish**:
- Due to the hypertonic nature of seawater, marine fish lose water. To counteract this, they have developed strategies such as minimizing urine production and actively drinking seawater.

**Hint**: Think about how marine fish adapt to losing water in a salty environment.

4. **Ion Regulation**:
- Marine fish actively expel excess salts, primarily monovalent ions (like sodium and chloride), through specialized cells called ionocytes. Divalent ions (like magnesium) are expelled through the kidneys.

**Hint**: Differentiate between the mechanisms for expelling monovalent and divalent ions.

5. **Evaluating the Options**:
- **Option A**: Entry of excess water in the body - Incorrect, as marine fish lose water.
- **Option B**: Removal of large quantities of urine - Incorrect, as marine fish produce minimal urine.
- **Option C**: Monovalent and divalent ions are expelled actively; loss of water from the body replenished by drinking seawater and eliminating monovalent ions respectively - Correct, as this accurately describes the osmoregulation process.
- **Option D**: Loss of divalent ions actively through ionocytes - Incorrect, as divalent ions are not expelled through ionocytes.

6. **Conclusion**:
- The correct statement regarding osmoregulation in the marine environment is **Option C**.

### Final Answer:
**C. Monovalent and divalent ions are expelled actively; loss of water from the body replenished by drinking seawater and eliminating monovalent ions respectively.**