Question

Pharyngeal nephridia of earthworm occurs in segment
(A) 3, 4 and 5
(B) 4, 5 and 6
(C) 5, 6 and 7
(D) 6, 7 and 8

Answer 1

Nephridia is a coiled tubular duct like structure. This structure is responsible for filtering and removing the waste from the body of earthworms. It is found in less developed organisms such as flatworms and annelids because they don’t have a kidney for excretion.

Complete answer:
Advanced organisms such as birds, mammals etc. have specialized organs for excretion. But less developed organisms such as flatworms, rotifers or earthworms have less developed organs. Birds and mammals have kidneys for excretion. But less advanced organisms have nephridia for excretion.
Nephridia are the excretory structures found in earthworms. These are the coiled, tubular and duct like structure. They are responsible for removing wastes from the body. Nephridia consists of funnel and tubular part. Funnel part collects the excess fluid from the coelomic chamber and then the tubular part transports this waste to the alimentary canal.
There are three types of nephridia found in earthworm:

Pharyngeal nephridia: As the name suggests pharyngeal, it means these nephridia are found in the pharyngeal region. These nephridia are found in the 4th, 5th and 6th segments in earthworm. They filter nitrogenous waste from the capillaries and then their ends are dumped into the pharynx and the buccal chamber.
Septal nephridia: These nephridia are found on both sides of septa. These are found after the 15th segment in the earthworm body. The excretory duct of nephridia open in the main gut cavity. These nephridia are responsible for osmoregulation and water balance in the body.
Integumentary nephridia: These are located throughout the body of earthworms. These are found from the 3rd to the last segment.

Pharyngeal nephridia are found in 4th, 5th and 6th segments in earthworm. That’s why the right answer is: B.

Note: Nephridia are the excretory organs which are responsible for removing the waste from the body. Their tubular part is connected with the alimentary canal and the funnel part is connected with the coelomic chamber. The funnel part is responsible for extracting the waste from the coelomic chamber whereas the tubular part is transported this waste to the alimentary canal.