Annelids respire through
Skin
Annelids respire by diffusion through the body surface. Setae help in locomotion in some annelids such as the earthworm. Nephridia are excretory organs found in most annelids. The clitellum is a thickened glandular and non-segmented section of the body wall near the head in earthworms and leeches. It is a thick, saddle-like ring found in the epidermis (skin) of the worm, usually with a light-coloured pigment. The clitellum is part of the reproductive system of a subgroup of annelids. To form a cocoon for its eggs, the clitellum secretes a viscous fluid. This organ is used in sexual reproduction of some annelids.