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.