Why nephridia in earthworm that are basically similar in structure classified into three types ? Mention the names of each.

Explanation

N ephridia are m ain excretory organs in earthworm. They are associated with excretion and regulation of water. Nephridia are present in all segments except first. Two segments on the basis of their location three types of nephridia are seen in earthworm. They are separated as enteronephric and exonephric. (exonephric - removal of nitrogenous waste done outside the body while in enteronephric, excretory waste is discharged in to lumen of intestine.) Septal nephridia : They are found attached to both sides of each intersegmental septum behind the `15^(th)` segment. It is enteronephric. Integumentary nephridia : They are attached to the inner side of the body wall from `3^(rd)` to last segment. They are exonephric. Pharyngeal nephridia : They are found as paired and lie one pair in each of the `4^(th), 5^(th)` and `6^(th)` segment. It is also enteronephric.