Question

Integumentary nephridia of earthworm occurs in
A) All segments except the first two
B) First two segments of the body
C) First fifteen segments
D) All the segments

Answer 1

Hint: Integumentary nephridia is small, with no nephrostome and no opening to the coelom.They are therefore referred to as the closed type of nephridia. In each segment of the body, from the 7th to the last segment, numerous nephridia are found attached to the lining of the body wall.

Complete answer:
Nephridia, coiled tubular duct-like organs, filter and remove waste from the body of the earthworm. In less developed worms, such as flatworms or rotifers, nephridia are not as specialized and are located in different cells throughout the body of the creature. In more advanced segmented worms, such as earthworms, nephridia is typically grouped in pairs across segments of the body of the worm.

Hundreds (200 to 250 per segment) of integumentary nephridia are located across the body wall of the earthworm (in all but the first two segments). These tiny nephritis are used to channel nitrogenous waste from the inside of the worm to the outer soil.

Integumentary nephridia occurs in all segments with the exception of the first two segments and varies from 200 to 250 per segment. The Clittellar segments are from 2000 to 2500 each. They are attached to the body wall and closed internally without nephrostomy. They only remove metabolic waste from the blood and are the smallest in size.

Thus, the correct answer is option ‘A’ i.e, All segments except the first two.

Note: Each integumentary nephridia is V-shaped with a short straight lobe and a twisted loop, the lumen of which has two ciliate canals. Each nephridium opens directly on the outer surface of the body wall with a nephridium. Since integumentary nephridia discharges excretory waste directly outside, it is called exonephric nephridia.