Planaria

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Planaria
Planaria torva.jpg
Planaria torva
Scientific classification OOjs UI icon edit-ltr.svg
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 have 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]

Contents

Description

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. [4]

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).

Diet

The food of Planaria species includes freshwater gastropods, tubificid worms, and freshwater arthropods, such as isopods of the genus Asellus and chironomid larvae. [5] In the United Kingdom, P. torva is a successful predator of the invasive New Zealand mud snail (Potamopyrgus jenkinsi). [6]

Species

The following species are recognised in the genus Planaria:

Application of planaria in research

These invertebrates are valuable models in toxicology, neuroscience, and pharmacology, offering ethical and cost-effective alternatives to vertebrate testing. Planaria’s simple nervous system, high sensitivity to environmental changes, and well-characterized genome make them particularly useful for studying chemical toxicity, wound healing, and neuroregeneration. Their ease of maintenance in laboratory settings further enhances their appeal for research. In pharmacology and neuroscience, planaria provide a unique opportunity to study the effects of psychoactive compounds, including investigations into drug addiction and withdrawal responses. [7] In drug delivery studies, they can be used to assess the biocompatibility and potential irritancy of pharmaceutical formulations, providing insight into their effects on biological tissues. [8] Additionally, their remarkable ability to regenerate lost body parts makes them an important model for stem cell research, offering insights into cellular and molecular mechanisms of regeneration.

Using advanced genetic analysis (phylogenomics), scientists confirmed that the family of land planarians, Geoplanidae, is divided into two main sister groups (clades):

One group consists of the subfamilies Bipaliinae and Microplaninae.

The other group consists of Rhynchodeminae and Geoplaninae. [9]

References

  1. ↑ Ivankovic, Mario; Haneckova, Radmila; Thommen, Albert; Grohme, Markus A.; Vila-Farré, Miquel; Werner, Steffen; Rink, Jochen C. (2019). "Model systems for regeneration: planarians". Development. 146 (17) dev167684. doi: 10.1242/dev.167684 . PMID   31511248.
  2. ↑ el-Showk, Sedeer (21 April 2014). "Unravelling How Planaria Regenerate". Scitable. Nature Education. Retrieved 26 January 2017.
  3. ↑ Jacobsen, Rowan (1 February 2024). "Brains Are Not Required When It Comes to Thinking and Solving Problems—Simple Cells Can Do It". Scientific American .
  4. ↑ 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.
  5. ↑ 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. Bibcode:1976FrBio...6..383R. doi:10.1111/j.1365-2427.1976.tb01623.x. ISSN   0046-5070.
  6. ↑ 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.
  7. ↑ 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.
  8. ↑ 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" . Toxicology in Vitro. 69 105004. Bibcode:2020ToxVi..6905004S. doi:10.1016/j.tiv.2020.105004. ISSN   0887-2333. PMID   33010358.
  9. ↑ Fernández, Rosa; Carbayo, Fernando; Mateos, Eduardo; Ángel Fernández-Álvarez, Fernando; Rojo, Iñaki; Salces-Ortiz, Judit; Escudero, Nuria; Benítez-Álvarez, Lisandra (September 2025). "Disentangling the evolutionary history of terrestrial planarians through phylogenomics". Molecular Phylogenetics and Evolution. 210 108371. Bibcode:2025MolPE.21008371B. doi:10.1016/j.ympev.2025.108371. PMID   40378903.


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