question_answer 5)

Distinguish between the followings (a) Prostomium and peristomium. (b) Septal nephridium and pharyngeal nephridium.

Answer:

(a) Prostomium and peristomium The first segment of earthworm with a ventral mouth is known as peristomium. Prostomium is a dorsal lobe which is present on the ventral mouth. (b) Septal nephridia and pharyngeal nephridia Septal nephridia are present on both the sides of inter segmental septa of segment 15 to the last that open into intestine. The pharyngeal nephridia are closed (no nephrostome) nephridia present as three paired groups (of about 100) in 4th, 5th and 6th segments.