What is Heteronereis?

Explanation

**Step-by-Step Solution:**

1. **Definition of Heteronereis**: Heteronereis is a specific reproductive phase observed in certain annelids, particularly in the genus Nereis.

2. **Location in the Body**: This phase is characterized by the presence of specialized structures located in the posterior part of the body of the organism. These structures are similar in size to the parapodia, which are lateral extensions used for locomotion.

3. **Function of Heteronereis**: The primary function of Heteronereis is to facilitate the release of gametes (sperm and eggs) into the surrounding seawater. This is achieved through active movement and the passing of seawater over the body.

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