The Echiura, or spoon worms, are a small group of marine animals. Once treated as a separate phylum, they are now considered to belong to Annelida. Annelids typically have their bodies divided into segments, but echiurans have secondarily lost their segmentation. The majority of echiurans live in burrows in soft sediment in shallow water, but some live in rock crevices or under boulders, and there are also deep sea forms. More than 230 species have been described. Spoon worms are cylindrical, soft-bodied animals usually possessing a non-retractable proboscis which can be rolled into a scoop-shape to feed. In some species the proboscis is ribbon-like, longer than the trunk and may have a forked tip. Spoon worms vary in size from less than a centimetre in length to more than a metre.
The gastrotrichs, commonly referred to as hairybellies or hairybacks, are a group of microscopic (0.06-3.0 mm), worm-like, pseudocoelomate animals, and are widely distributed and abundant in freshwater and marine environments. They are mostly benthic and live within the periphyton, the layer of tiny organisms and detritus that is found on the seabed and the beds of other water bodies. The majority live on and between particles of sediment or on other submerged surfaces, but a few species are terrestrial and live on land in the film of water surrounding grains of soil. Gastrotrichs are divided into two orders, the Macrodasyida which are marine, and the Chaetonotida, some of which are marine and some freshwater. Nearly 800 species of gastrotrich have been described.
The Naididae are a family of clitellate oligochaete worms like the sludge worm, Tubifex tubifex. They are key components of the benthic communities of many freshwater and marine ecosystems. In freshwater aquaria they may be referred to as detritus worms.
Sabellidae, or feather duster worms, are a family of marine polychaete tube worms characterized by protruding feathery branchiae. Sabellids build tubes out of a tough, parchment-like exudate, strengthened with sand and bits of shell. Unlike the other sabellids, the genus Glomerula secretes a tube of calcium carbonate instead. Sabellidae can be found in subtidal habitats around the world. Their oldest fossils are known from the Early Jurassic.
Atriolum robustum is a colonial tunicate or sea squirt in the family Didemnidae. It is native to the western and central Indo-Pacific where it is usually found anchored to a hard surface in shallow water.
Aeolosoma is a genus of minute annelid worms, variously attributed either to oligochaetes or polychaetes. Unlike most polychaetes, they reside in freshwater environments in various parts of the world.
Didemnum vexillum is a species of colonial tunicate in the family Didemnidae. It is commonly called sea vomit, marine vomit, pancake batter tunicate, or carpet sea squirt. It is thought to be native to Japan, but it has been reported as an invasive species in a number of places in Europe, North America and New Zealand. It is sometimes given the nickname "D. vex" because of the vexing way in which it dominates marine ecosystems when introduced into new locations, however the species epithet vexillum actually derives from the Latin word for flag, and the species was so named because of the way colonies' long tendrils appear to wave in the water like a flag.
Amathia vidovici is a species of colonial bryozoans with a tree-like structure. It is found in shallow waters over a wide geographical range, being found in both the Atlantic and Pacific Oceans and adjoining seas.
Amathia verticillata, commonly known as the spaghetti bryozoan, is a species of colonial bryozoans with a bush-like structure. It is found in shallow temperate and warm waters in the western Atlantic Ocean and the Caribbean Sea and has spread worldwide as a fouling organism. It is regarded as an invasive species in some countries.
Lepidodermella squamata is a freshwater species of minute worm in the phylum Gastrotricha.
Thelepus cincinnatus is a species of polychaete annelids in the family Terebellidae, which can be found inhabiting a tube of secrete on rocks and shells. The worm is widely distributed, and can be found in almost any region of the oceans at depths ranging from 10 to 4000 meters.
Cryptosula pallasiana is a species of colonial bryozoan in the order Cheilostomatida. It is native to the Atlantic Ocean where it occurs in northwestern Europe and northern Africa, and the eastern seaboard of North America. It has been accidentally introduced to the western coast of North America and to other parts of the world.
Watersipora subtorquata, commonly known as the red-rust bryozoan, is a species of colonial bryozoan in the family Watersiporidae. It is unclear from where it originated but it is now present in many warm-water coastal regions throughout the world, and has become invasive on the west coast of North America and in Australia and New Zealand.
Allolobophora chlorotica, commonly known as the green worm, is a species of earthworm that feeds and lives in soil. This species stands out from other earthworms due to the presence of three pairs of sucker-like discs on the underside of the clitellum. An examination of A. chlorotica specimens from many parts of the British Isles suggests that there are two forms of this species, one with green pigment in the body wall, and one which lacks this pigment, making it pink.
Polydora ciliata is a species of annelid worm in the family Spionidae, commonly known as a bristleworm. It is a burrowing worm and is found in the northeastern Atlantic Ocean and some other parts of the world.
Tracheloraphis is a genus of ciliates in the family Trachelocercidae.
Eurypanopeus depressus, the flatback mud crab or depressed mud crab, is a true crab belonging to the infraorder Brachyura and the family Panopeidae. It is native to the western Atlantic Ocean and is often found in estuaries and lagoons, commonly living in close association with oysters.
Ochetostoma erythrogrammon is a species of spoon worm in the family Thalassematidae. It is found in shallow water in the Atlantic Ocean, the Mediterranean Sea, and the Indian and Pacific Oceans, burrowing in soft sediment.
Podostemum ceratophyllum, commonly known as the hornleaf riverweed, is a species of submerged aquatic plant in the family Podostemaceae. It is native to eastern North America where it grows on hard bottoms in swiftly flowing rivers and streams and is considered a foundation species.
Crisularia plumosa is a species of bryozoan belonging to the family Bugulidae, commonly known as the feather bryozoan. It is native to the Atlantic Ocean.
