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Planaria torva
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Order: Tricladida
Family: Planariidae
Genus: Planaria
OF Müller, 1776

Planaria is a genus of planarians in the family Planariidae. Due to its excellent ability to regenerate, species of Planaria has also been used as model organisms in regeneration studies.[1] When an individual is cut into pieces, each piece has the ability to regenerate into a fully formed individual.[2] When decapitated, they retain their memories.[3]

Various species of Planaria have been widely used as model invertebrate organisms in pharmacological research, in particular in the studies of the drugs of abuse.[4] They were also proposed as models in toxicological research.[5]


Currently the genus Planaria is defined as freshwater triclads with oviducts that unite to form a common oviduct without embracing the bursa copulatrix and with an adenodactyl present in the male atrium. The testes occur along the whole body.[6]

Planaria originally have habitats in dark, murky water which results in such sensitivity (Paskin et al., 2014). They are also sensitive to other stimuli such as chemical gradients, vibration, magnetic and electric fields (Deochand et al., 2018). Their central nervous system includes the anterior (head, brain and eyes) and middle (abdominal trunk and pharynx) (Deochand et al., 2018).


The food of Planaria species includes freshwater gastropods, tubificid worms, and freshwater arthropods, such as isopods of the genus Asellus and chironomid larvae.[7] In the United Kingdom, P. torva is a successful predator of the invasive New Zealand mud snail (Potamopyrgus jenkinsi).[8]


The following species are recognised in the genus Planaria:


  1. ^ "Model systems for regeneration: planarians". doi:10.1242/dev.167684. Retrieved 21 January 2023.
  2. ^ "Unravelling How Planaria Regenerate". Sedeer el-Showk. Retrieved 26 January 2017.
  3. ^
  4. ^ Raffa, Robert B. (3 December 2008). Planaria: A Model for Drug Action and Abuse. CRC Press. doi:10.1201/9781498713597. ISBN 978-0-429-08997-8.
  5. ^ Shah, Syed Ibrahim; Williams, Adrian C.; Lau, Wing Man; Khutoryanskiy, Vitaliy V. (1 December 2020). "Planarian toxicity fluorescent assay: A rapid and cheap pre-screening tool for potential skin irritants" (PDF). Toxicology in Vitro. 69: 105004. doi:10.1016/j.tiv.2020.105004. ISSN 0887-2333. PMID 33010358. S2CID 222159871.
  6. ^ Ball, Ian R.; Reynoldson, T. B.; Warwick, T. (2009). "The taxonomy, habitat and distribution of the freshwater triclad Planaria torva (Platyhelminthes: Turbellaria) in Britain". Journal of Zoology. 157 (1): 99–123. doi:10.1111/j.1469-7998.1969.tb01691.x. ISSN 0952-8369.
  7. ^ Reynoldson, T. B.; Sefton, A. D. (1976). "The food of Planaria torva (Müller) (Turbellaria-Tricladida), a laboratory and field study". Freshwater Biology. 6 (4): 383–393. doi:10.1111/j.1365-2427.1976.tb01623.x. ISSN 0046-5070.
  8. ^ Reynoldson, T. B.; Piearce, Bronwen (1979). "Predation on snails by three species of triclad and its bearing on the distribution of Planaria torva in Britain". Journal of Zoology. 189 (4): 459–484. doi:10.1111/j.1469-7998.1979.tb03974.x. ISSN 0952-8369.