Question

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

Answer 1

Hint: Earthworm belongs to the phylum Annelida, under class Oligochaeta and genus Lumbricus.
The major function of nephridia is the removal of waste products from the body of the earthworm. These are basically ciliated tubes that collect and excrete the waste products (surplus ions, metabolic waste, food, toxins, and other useless hormonal products) outside the body. They direct these products towards a funnel-shaped structure called nephrostomes.

Complete answer:
There are three types of nephridia found in the body of earthworm based on their location:
Septal Nephridia: These are present on both the sides of the intersegmental septa which is located behind the 15th segment. These tubes open into the intestine.
Integumentary nephridia: These are present from the 3rd segment to the last segment. These remain attached to the body wall and open into the outer environment. These are the most abundant nephridia present in earthworms.
Pharyngeal nephridia: These are present as paired tufts in 4th, 5th, and 6th segments.

Note:
The learner should have a clear distinction between protonephridia and metanephridia. The metanephridia is an excretory gland which consists of a ciliated funnel-shaped opening into the cavity of the body and it opens to the exterior environment in the body wall. It functions as an excretory gland that eliminates waste products from the body.
On the other hand, the protonephridia are dead tubules and their end parts are known as flame cells. They function as osmoregulatory organs for the entire body.
Apart from this, there are other types of nephridia present known as saccate metanephridia which are excretory glands and have the function as metanephridia. These are found in the majority of arthropods, crustaceans and arachnids.