Closed circulatory system. Swim free, burrow in sand, or live in tubes cemented with mucus. Parapodia are paddle-like appendages extending from each segment. Function in locomotion and gas exchange. One species releases sperm and eggs within 2 hours of each other.
Cuticle is thin, transparent and keeps body from drying out.
Cuticle secreted by epidermal cells. Mucus secreted by epidermal gland cells also protects from desiccation. Body wall has outer circular and inner longitudinal muscles. Food Worm takes in soil and decaying plants, so soil is turned and aerated. Worm also discharges nitrogenous waste, which helps plants grow Food in through muscular pharynx to esophagus.