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Earthworm Excretory System Short Notes

In this article we will discuss about the earthworm excretory system

Earthworm Excretory System

The excretory system remove metabolic wastes and toxins from the body
Excretory organs of earthworm is nephridia
Nephridia occur in all segments of the body except for the first three
The earthworms are both ureotelic and ammonotelic and secrete both urea and ammonia as waste products

Nephridia

According to their position in the body, nephridia are of 3 types:- Septal Nephridia, Integumentary nephridia and Pharyngeal nephridia

1. Septal Nephridia

They are well developed and the largest nephridia
Found on inter segmental septa
Starting from 15 segment all posterior septa have nephridia
Each inter-segmental septum possess two rows of septal nephridia (80-100 on each septum)
Septal nephridium has 4 parts: Nephrostome (nephridiostome or ciliated funnel), neck, body of nephridium and terminal duct
Septal nephridia open into alimentary canal
Alimentary canal absorbs water from excretory materials

Function of septal nephridia

Septal nephridia discharge the waste products through canal and ducts into the lumen of the intestine. So they are enteronephric.

2. Integumentary nephridia

Present on the internal surface of body wall
Each segment has 200-250 nephridia
In clitellar segments has 2000-2500 nephredia. They are known as forest of nephridia
Each nephridium opens by a nephridiopore on the outer surface of the body wall directly.

Function of Integumentary nephridia

They discharge nitrogenous metabolic waste products directly outside from the body through nephridiopores. So they are called exonephric nephridia.

3. Pharyngeal nephridia

Present on 4,5,6 segment of alimentary canal
Similar to septal nehridia in structure but they lack nephrostome
Terminal ducts of each group unit to form a common duct
Common ducts open into pharynx in 4 segment

Function of Pharyngeal nephridia

They discharge the waste products directly into the buccal cavity and pharynx from where these are passed outside with undigested food through the anus. So they are called enteronephric nephridia.

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