What Does Prostomial Mean?

The prostomium is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth.

What is meant by prostomium?

: the portion of the head of an annelid worm (such as an earthworm) that is situated in front of the mouth.

What is the prostomium used for?

There is a small tongue-like lobe just above the mouth called the prostomium (see figure 1). Earthworms use the prostomium to see their environment, as earthworms have no eyes, ears, nose or hands. They depend on the prostomium and skin to help it feel their way through the soil.