For example, the lugworms have a simple, thin-walled, jawless proboscis, which is used to draw sand into the gut, where organic matter is removed. Other worms have feeding tentacles that extend from the tube opening and creep along the mud or sand, picking up organic deposits. The tentacles are quickly withdrawn if the animal is startled. The parapodia are reduced in the sedentary polychaetes, and the setae of many tube-dwelling forms are hooked to help the worm hold itself to the wall of its tube. The structure of the digestive tract of polychaetes is variable, reflecting the diversity of feeding types.
Respiration is entirely through the body wall in some polychaetes, and partially so in most.
The tentacles of feather-duster worms are used for respiratory exchange as well as for feeding. A polychaete may have a single pair of excretory tubes or a pair in each segment. Sedentary polychaetes have various modifications to insure that wastes will be deposited near the mouth of the tube or burrow, where they are washed away. Polychaete Reproduction Most polychaetes reproduce sexually, and the sexes are separate. Sex cells develop from masses of tissue in the metameres and leave by way of tubules or by rupture of the body wall.