Tomopteris from plankton

The Polychaeta or Polychaetes are a class of annelid worms, generally marine, with a pair of fleshy protrusions on each body segment called parapodia that bear many bristles, called setae, which are made of Chitin. Polychaeta means "many-bristled" (as opposed to the Oligochaeta which are "few-bristled"), and indeed the polychaetes are sometimes referred to as bristle worms. More than 10,000 species are described in this class, but common representatives are the lugworm (Arenicola marina) and the sandworm or clam worm Nereis. Image File history File links Download high resolution version (1061x722, 128 KB)tomopterus image uwe kils gfdl self File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1061x722, 128 KB)tomopterus image uwe kils gfdl self File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Tomopteris from plankton - a polychaete ... Photomontage of plankton organisms Plankton are drifting organisms that inhabit the water column of oceans, seas, and bodies of fresh water. ... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata    Oligochaeta - Earthworms and others    Acanthobdellida    Branchiobdellida    Hirudinea - Leeches Class Myzostomida Class Archiannelida (polyphyletic) Class Echiura *Some authors consider the subclasses under Clitellata to be classes The annelids, collectively called Annelida (from Latin annellus little ring), are a large phylum of animals, comprising... Parapodia (almost feet) are paired lateral outgrowths, bearing bristles known as chaetae. ... Structure of chitin molecule In biology, chitin (pronounced keye-tin) is one of the main components in the cell walls of fungi, the exoskeletons of insects and other arthropods, and in some other animals. ... Orders Arhynchobdellida Haplotaxida Rhynchobdellida The Oligochaeta or few-bristled worms (singular Oligochaete, IPA /ˈɒlɪgoʊˌkit/) are well-segmented Annelids, most with a spacious coelom that is used as a hydroskeleton. ... The Lugworm ia a large marine worm of the phylum Annelida much used as bait by anglers. ... A sandworm is a Polychaete in the genus Nereis. ... Binomial name Nereis succinea (Frey & Leuchart, 1847) The Common clam worm Nereis succinea is a widely distributed polychaete worm. ...

The polychaetes' paddle-like and highly vascularized parapodia are used for movement and act as the animal's primary respiratory surface (parapodia can be thought of as a kind of external gills that are also used for locomotion). Polychaeta also have well-developed heads compared to other annelids. Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anenomes) Placozoa {trichoplax) Subregnum Bilateria (bilateral symmetry) Acoelomorpha (basal) Orthonectida (flatworms, echinoderms, etc. ... Gas exchange or respiration takes place at a respiratory surface - a boundary between the external environment and the interior of the body. ... gills of a Smooth Newt In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ...

Taxonomically, the polychaetes are thought to be paraphyletic, meaning an assemblage of not very closely related forms, but all of which come from the same source. Paraphyletic - Wikipedia /**/ @import /skins-1. ...

Polychaetes are extremely variable in both form and lifestyle and include freeliving (with many swimming among plankton), burrowing, and tube-dwelling species as well as commensals. The free living forms or Errantia tend to have well-developed sense organs and jaws, while the Sedentaria (or stationary forms) lack them but may have specialized gills or tentacles used for respiration and filter-feeding, similar to the fanworms. Photomontage of plankton organisms Plankton are drifting organisms that inhabit the water column of oceans, seas, and bodies of fresh water. ...

One notable polychaete, the Pompeii worm (Alvinella pompejana) is endemic to the hydrothermal vents of the Pacific Ocean. Pompeii worms are thought to be the most heat-tolerant complex animals known. Binomial name Alvinella pompejana The Pompeii worm (Alvinella pompejana) is a deep-sea polychaete worm found only at hydrothermal vents in the Pacific Ocean. ... A hydrothermal vent A hydrothermal vent is a fissure in a planets surface from which geothermally heated water issues. ...

Another remarkable polychaete is Hesiocaeca methanicola, which lives on methane clathrate deposits. Binomial name Hesiocaeca methanicola Recently, methane clathrate deposits in the ocean floor have been found to be inhabited by polychaete worms of the species Hesiocaeca methanicola. ... Burning ice. Methane released by heating burns, water drips. ...

Reference

• Campbell, Reece, and Mitchell. Biology. 1999.