Anal gills occur in

Options

A. Doris
B. Limax
C. Slug
D. Nautilus

Answer

To determine where anal gills occur among the given options, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks about the occurrence of anal gills in specific organisms. We need to identify which of the given options has anal gills.

2. **Identify the Organisms**: The options provided are Doris, Lemax, Slug, and Nautilus. We need to analyze each of these organisms to see if they possess anal gills.

3. **Define Anal Gills**: Anal gills are gills that are located near the anus of an organism. They are typically found in some aquatic mollusks and are involved in respiration.

4. **Analyze Each Option**:
- **Doris**: Known as sea hares, Doris has its anus located in the mid-dorsal region, surrounded by gills. This is a key feature that indicates the presence of anal gills.
- **Lemax**: This organism does not have anal gills; its gills are located elsewhere.
- **Slug**: Similar to Lemax, slugs do not have anal gills; they have gills positioned in different areas.
- **Nautilus**: Nautilus has a different respiratory structure and does not possess anal gills.

5. **Conclusion**: Based on the analysis, Doris is the only organism among the options that possesses anal gills. Therefore, the correct answer is Doris.

### Final Answer:
Anal gills occur in **Doris**.

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