Nereis is a genus of polychaete worms in the family Nereididae. It comprises many species, most of which are marine. Nereis possess setae and parapodia for locomotion and gas exchange. They may have two types of setae, which are found on the parapodia. Acicular setae provide support. Locomotor setae are for crawling, and are the bristles that are visible on the exterior of the Polychaeta. They are cylindrical in shape, found not only in sandy areas, and they are adapted to burrow. They often cling to seagrass (posidonia) or other grass on rocks and sometimes gather in large groups.
Eunicidae is a family of marine polychaetes. The family comprises marine annelids distributed in diverse benthic habitats across Oceania, Europe, South America, North America, Asia and Africa. The Eunicid anatomy typically consists of a pair of appendages near the mouth (mandibles) and complex sets of muscular structures on the head (maxillae) in an eversible pharynx. One of the most conspicuous of the eunicids is the giant, dark-purple, iridescent "Bobbit worm", a bristle worm found at low tide under boulders on southern Australian shores. Its robust, muscular body can be as long as 2 m. Eunicidae jaws are known from as far back as Ordovician sediments. Cultural tradition surrounds Palola worm reproductive cycles in the South Pacific Islands. Eunicidae are economically valuable as bait in both recreational and commercial fishing. Commercial bait-farming of Eunicidae can have adverse ecological impacts. Bait-farming can deplete worm and associated fauna population numbers, damage local intertidal environments and introduce alien species to local aquatic ecosystems.
Terebellida make up an order of the Polychaeta class, commonly referred to as "bristle worms". Together with the Sabellida, the Spionida and some enigmatic families of unclear taxonomic relationship, they make up the subclass Canalipalpata, one of the three main clades of polychaetes. Like most polychaetes, almost all members of the Terebellida are marine organisms. Most are small, sessile detritivores which live in small tubes they build from mud or similar substrate, or burrow in the sand. Their central nervous system displays characteristic apomorphies.
Ampharetidae are a family of terebellid "bristle worm". As such, they belong to the order Canalipalpata, one of the three main clades of polychaetes. They appear to be most closely related to the peculiar alvinellids (Alvinellidae) which inhabit the deep sea, and somewhat less closely to the well-known trumpet worms (Pectinariidae). These three appear to form one of the main clades of terebellids.
Psamathini are a tribe of phyllodocid "bristle worms" in the family Hesionidae. They are marine organisms; most are found on the continental shelf, but some have adapted to greater depths down to the abyssal plain.
Acrocirridae is a family of polychaete worms. Acrocirrids are detritivores, catching falling particles with numerous long prostomial tentacles. There are eight known genera, and at least 21 described species and subspecies within the Acrocirridae. The acrocirrids are primarily benthic (seabed-dwelling) animals, but at least two genera appear to have evolved or adapted to a pelagic (free-swimming) habitat.
Phyllodocida is an order of polychaete worms in the subclass Aciculata. These worms are mostly marine, though some are found in brackish water. Most are active benthic creatures, moving over the surface or burrowing in sediments, or living in cracks and crevices in bedrock. A few construct tubes in which they live and some are pelagic, swimming through the water column. There are estimated to be more than 4,600 accepted species in the order.
Errantia is a diverse group of marine polychaete worms in the phylum Annelida. Traditionally a subclass of the paraphyletic class Polychaeta, it is currently regarded as a monophyletic group within the larger Pleistoannelida, composed of Errantia and Sedentaria. These worms are found worldwide in marine environments and brackish water.
Amphinomidae, also known as the bristle worms or sea mice, are a family of marine polychaetes, many species of which bear chaetae mineralized with carbonate. The best-known amphinomids are the fireworms, which can cause great pain if their toxin-coated chaetae are touched or trodden on. Their relationship to other polychaete groups is somewhat poorly resolved.
Chrysopetalidae is a family of polychaete worms. The body is short or elongated, with few or numerous segments. All segments bear on their dorsal side a fan or a transverse row of paleae. The cephalic lobe has tentacles and eyes and the buccal segment has two or four tentacular cirri on each side. The parapodia are uniramous or biramous, with dorsal cirri upon all segments. The ventral bristles are compound.
Phyllodocidae is a family of polychaete worms. Worms in this family live on the seabed and may burrow under the sediment.
Leocratides is a genus of marine hesionid polychaete worms dwelling in hexactinellid sponges.
Flabelligeridae is a family of polychaete worms, known as bristle-cage worms, notable for their cephalic cage: long slender chaetae forming a fan-like arrangement surrounding the eversible head. Unlike many polychaetes, they also have large, pigmented, complex eyes.
Subadyte pellucida is a scale worm widely reported from the Indian, Pacific and North Atlantic Oceans from the intertidal zone to depths of about 800 m.
Sedentaria is a diverse clade of annelid worms. It is traditionally treated as a subclass of the paraphyletic class Polychaeta, but it is also a monophyletic group uniting several polychaetes and the monophyletic class Clitellata. It is the sister group of Errantia.
Notoproctus is a genus of marine polychaete worms in the family Maldanidae. It is the only member of the subfamily Notoproctinae.
Buskiella is a genus of pelagic polychaete annelids placed either in the family Flotidae or Flabelligeridae. In appearance, they are generally bluish or yellowish, depending on lighting conditions, and live exclusively in very deep water. They move by swinging their bodies from side to side, "rowing with [their] bristles." Species have nine to eleven chaetigers.
Flotidae is a family of pelagic polychaete worms, sometimes synonymized with Flabelligeridae, which they closely resemble. Other sources consider them the sister taxon to Flabelligeridae and closely allied to the latter group.
Flabelligera is a genus of polychaetes in the family Flabelligeridae. Species are common around the world, in both temperate and cold waters. Flabelligera species have long, club-like papillae, which are encased in a smooth mucus sheath. They also have a distinct cephalic cage, and hooked neurochaeatae which they use to hold onto rocks.
Amphicteinae is a subfamily of polychaete worms in the family Ampharetidae. It was originally established as a tribe, with eight genera, but was elevated to subfamily-level with a reduced number of genera in 2020. Two species, Hypaniola kowatewskii and Hypania invalida, are known to feed on blue-green algae.
