Question

Enteronephric nephridia of earthworm are
a. Pharyngeal and septal
b. Pharyngeal
c. Septal
d. Integumentary

Answer 1

Hint: Many invertebrates comprise a tubular structure which is used as an excretory organ. Along with excretion nephridia also takes part in osmoregulation of the body. Nephridia is found in annelids, arthropods, and Mollusca.

Complete answer:
Earthworms possess a tubular duct-like organ that is responsible for the filter and removal of waste materials from their body. Nephridia in earthworms are located throughout the body in paired form.
There are three types of nephridia found in an earthworm. These are Enteronephric septal nephridia, Integumentary nephridia, and enteronephric pharyngeal nephridia.

Enteronephric septal nephridia:
- It is a thread-like structure.
- Septal nephridia are located on both sides of septa.
- After the $15^{th}$ segment of the body septal nephridia appear and exit out to the main gut cavity in a pair of the duct.

Integumentary nephridia:
- Integumentary nephridia are a very small single opening.
- Integumentary nephridia are found throughout the segments of the earthworm.
-Each segment comprises 200-250 nephridia

Enteroierphric pharyngeal nephridia:
- Enteronephric pharyngeal nephridia comprise cylindrical brunch-like structure which are located around the esophagus.
- Pharyngeal nephridia comprise a larger number of smaller nephridia.
- Pharyngeal nephridia are located in clustered form into three sets of a paired tusk.
- These three sets of paired ducts open into the pharynx and buccal chamber.

Hence, the correct answer is option (A).

Note: Nephridia acts like the kidney. Pharyngeal nephridia help to excrete out the nitrogenous waste from the surrounding capillaries. The major function of integumentary nephridia is to excrete out the nitrogenous waste from the earthworm's body. Septal nephridia regulates osmoregulation in the earthworm.