Coloured scanning electron micrograph (SEM) of The Polychaeta are a class of annelid worms, generally marine. Polychaetes range from microscopic to 10 feet long, the average being 4 inches. Most polychaetes crawl on the ocean floor, but others have modified body structures to adapt to various ecological niches. Augeneriella dubia, a microscopic polychaete (also known as a micro-polychaete, feather duster worm, bristle worm or fan worm), has a segmented body topped by a radial crown made up of 3 pairs of finger-like radioli (tentacles, shown here) that function in filter feeding and respiration. The head includes a pair of antennae, tentacle-like palps (only 1 palp is shown here), and a pair of cilia-lined pits known as nuchal organs. These appear to be chemoreceptors that help the worm find food. Each body segment has a pair of fleshy protrusions (parapodia) bearing many chitinous bristles (chaetae) used for movement. Magnification x35 when shortest |