.............. is a ............. fish in which male has a brood pouch when female lays eggs.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a specific type of fish that has a unique reproductive feature where the male possesses a brood pouch for the eggs laid by the female.

2. **Identifying the Brood Pouch**: A brood pouch is defined as a specialized cavity or sac in the body of an animal where eggs are received and undergo development.

3. **Identifying the Fish**: The fish that is known for having a brood pouch is the seahorse.

4. **Scientific Classification**: Seahorses belong to the genus *Hippocampus*.

5. **Reproductive Process**: In seahorses, the female lays her eggs into the male's brood pouch. This is a unique characteristic as it is the male that incubates and nourishes the embryos.

6. **Development Duration**: The eggs typically remain in the male's brood pouch for about 45 days, depending on the species, until they hatch.

7. **Final Answer**: Therefore, the complete answer to the question is: "Seahorse is a marine fish in which male has a brood pouch when female lays eggs."

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