Question

Why are nephridia in earthworms that are basically similar in structure classified into three types? Mention the names of each.

Answer 1

Structure:

Nephridium is an excretory organ found in annelids like earthworms. Nephridium has two main parts

• Funnel or nephrostome
• the tubular part

This is the basic structure of all nephridia.


Classification:

Nephridia are classified as follows:-

• Septal nephridia
• Integumentary nephridia
• Pharyngeal nephridia

Although all the nephridia have the same structure, they are present in different locations and empty wastes in different locations as well.

Septal nephridia:

Septal nephridia is present on both sides of the intersegmental septum of segment 15 to the last segment. These nephridia open into the intestine.


Integumentary nephridia:

Integumentary nephridia is found attached to the lining of the body wall from the 3rd segment to the last. They open into the exterior of the body through nephridiopores.


Pharyngeal nephridia:

Pharyngeal nephridia is present as three pairs of tufts on 4th, 5th and 6th segment and open into the buccal cavity and pharynx.