Prostomium is a small lip or tongue like lobe present on the upper side of mouth. ... The dorsal surface of prostomium contains photoreceptor cells which help them to detect the intensity and duration of light. Hence, prostomium serves sensory function.

Is prostomium sensory structure?

Description. The prostomium is part of the head and holds at least part of the brain and often bears sensory structures such as the eyes, antennae and palps. ... Another sensory organ, the nuchal organ (or a variation, the nuchal epaulette), is a chemosensory, ciliated pit or groove at the posterior end of the prostomium.

What is the function of the prostomium?

The prostomium is a lobe that serves as a covering for the mouth and as a wedge to force open cracks in the soil into which the earthworm may crawl 1. The anterior section of the worm is shown in Figure 1. Another key characteristic is the clitellum, or the collar-like structure near the front of worm's body.