Planarians (triclads) are free-living flatworms of the class Turbellaria, order Tricladida, which includes hundreds of species, found in freshwater, marine, and terrestrial habitats. Planarians are characterized by a three-branched intestine, including a single anterior and two posterior branches. Their body is populated by adult stem cells called neoblasts, which planarians use for regenerating missing body parts. Many species are able to regenerate any missing organ, which has made planarians a popular model in research of regeneration and stem cell biology. The genome sequences of several species are available, as are tools for molecular biology analysis.
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.
Dugesia is a genus of dugesiid triclads that contains some common representatives of the class Turbellaria. These common flatworms are found in freshwater habitats of Africa, Eurasia, and Australia. Dugesia is best known to non-specialists because of its regeneration capacities.
Planariidae is a family of freshwater planarians.
Pseudoceros is a genus of the flatworms Platyhelminthes.
Geoplanidae is a family of flatworms known commonly as land planarians or land flatworms.
Bipalium is a genus of large predatory land planarians. They are often loosely called "hammerhead worms" or "broadhead planarians" because of the distinctive shape of their head region. Land planarians are unique in that they possess a "creeping sole", a highly ciliated region on the ventral epidermis that helps them to creep over the substrate. Native to Asia, several species are invasive to the United States, Canada, and Europe. Some studies have begun the investigation of the evolutionary ecology of these invasive planarians.
Doris is a genus of sea slugs, specifically dorid nudibranchs. These animals are marine gastropod molluscs in the family Dorididae.
Dugesiidae is a family of freshwater planarians distributed worldwide. The type genus is Dugesia Girard, 1850.
Girardia is a genus of freshwater planarians belonging to the family Dugesiidae.
Schmidtea is a genus of freshwater triclads. Species of the genus Schmidtea are widely used in regeneration and developmental studies.
Dendrocoelidae is a family of freshwater tricladida flatworms that has a holarctic distribution.
Girardia tigrina, known as the brown planarian or the immigrant triclad flatworm, is a species of dugesiid native to the Americas. It has been accidentally introduced into Europe and Japan.
Schmidtea polychroa is a species of freshwater flatworm, a dugesiid triclad that inhabits the shallow mesotrophic or eutrophic waters of rivers and lakes of Europe. It is also present in North America, where it has been introduced at least in the Saint Lawrence river system. It is an animal with a limited dispersion capability.
Microplana is a genus of land planarians found in Europe and Africa.
Dendrocoelum is a genus of freshwater triclad. Over one hundred species have been described.
Josef Hauser S. J. was a Hungarian zoologist and Jesuit priest.
Planaria torva is a species of planarian in the family Planariidae. When an individual is cut into pieces, each piece has the ability to regenerate into a fully formed individual.
Dendrocoelum lacteum, the milk-white planarian, is a freshwater planarian found in lakes and running waters in Europe, being the most widespread freshwater planarian in this continent.
Cerebratulus is a genus of nemerteans belonging to the family Lineidae.
