Answer the following: 

a. What is the function of nephridia? 

b. How many types of nephridia are found in earthworms based on their location?

Nephridia in Earthworms

Nephridia play a crucial role in the excretory system of earthworms by removing waste products from the body. These organs help maintain the organism’s internal environment by eliminating metabolic wastes, excess ions, toxins, and other unnecessary substances.

Metanephridia are the primary excretory glands in earthworms. Each metanephridium has a ciliated funnel that opens into the body cavity and leads to a tubule, which finally opens to the exterior of the body. The cilia help in directing waste materials toward the funnel-shaped structures called nephrostomes, ensuring efficient excretion.

Protonephridia, on the other hand, are closed-end tubules whose terminal cells are called flame cells. These primarily function in osmoregulation, helping maintain the balance of water and salts in the body.

Types of Nephridia in Earthworms

Nephridia are classified based on their location in the body:

1. Septal Nephridia:
   • Found on both sides of the intersegmental septa behind the 15th segment.
   • Open into the intestine to release waste.
2. Integumentary Nephridia:
   • Present from the 3rd to the last segment.
   • Open onto the body surface and are attached to the body wall.
3. Pharyngeal Nephridia:
   • Occur as paired tufts in the 4th, 5th, and 6th segments.