What are Polychaetes?
The class Polychaeta (poly-keet-a, meaning “many bristles”) consists of a very diverse group of segmented worms (unlike round worms or flatworms, which are not segmented) which primarily live in ocean habitats. The closest relatives of polychaetes are the earthworms and leeches. Among the over 80 polychaete families and more than 10,000 species there is an amazing array of body forms and sizes. Polychaete worms live in every type of habitat in the seas – they can be found in the sands of any beach, all the way down to the deepest depths of the oceans. Most polychaetes make the sea floor their home, where they burrow through sand and mud, or crawl over the sediment surface. Because of their vast abundance, polychaetes comprise an extremely important link in ocean food chains. As a result, polychaetes are one of the most important groups of organisms for assessing the health of marine ecosystems. Although polychaetes are largely unknown to most people that visit the seashore, our underst
Polychaetes are a class of ubiquitous segmented worms, mostly marine, though a few species have adapted to terrestrial life in humid areas. They are annelids, the marine counterparts of terrestrial annelids like earthworms. “Polychaete” means “many hairs,” a reference to the chitinous hairs that protrude from either side of their bodies, with an identical set of hairs per segment. Like terrestrial annelids, polychaetes have an advantage over simpler worms due to their segmentation, which helps give them a more rigid structure more conducive to secondary adaptations. Like a few other common animal phyla, polychaetes have been around since the Lower Cambrian, approximately 540 million years ago. Definitive polychaete fossils have been found in the Sirius Passet Lagerstatte, alongside primitive arthropods. They may date back to even earlier, as segmented hollow skeleton tubes (Cloudina) have been found from the Ediacaran, reminiscent of the tubes used by some modern polychaetes, though co
