Ammonia is the chief nitrogenous excretory material in.............

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about which organisms primarily excrete ammonia as their nitrogenous waste product.

2. **Defining Ammonotelic Organisms**: Ammonotelic organisms are those that excrete ammonia directly into the environment. This is typically seen in aquatic organisms where ammonia can be diluted in water.

3. **Identifying Examples of Ammonotelic Organisms**: Freshwater fish are a classic example of ammonotelic organisms. They excrete ammonia because they live in water, which allows for the rapid diffusion of ammonia into the surrounding environment.

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