Question

Choose the incorrect statement about earthworms:

• A. Segmentally arranged coiled tubules known as nephridia act as an excretory organ
• B. Septal nephridia and pharyngeal nephridia are enteronephric
• C. Integumentary nephridia is exonephric
• D. Integumentary and septal nephridia are exonephric

Answer 1

The correct option is D Integumentary and septal nephridia are exonephric

In earthworms, excretory organs occur as segmentally arranged coiled tubules called nephridia.
These are of three types:
1. Septal nephridia - Present from segment 15 onwards till the last that opens into the intestine. Such nephridia which discharge into the intestine are called enteronephric.
2. Integumentary nephridia - Present from segment 3 onwards and opens on the body surface. Such nephridia are called exonephric.
3. Pharyngeal nephridia - Present as three paired tufts in the 4th, 5th and 6th segments. The terminal duct of the tuft opens to the common thick walled duct. The common duct of 6th segment opens into the buccal chamber and that of 4th and 5th opens into the pharynx. They are enteronephric.
So septal and pharyngeal nephridia are enteronephric. Integumentary nephridia are exonephric.