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. When an individual is cut into pieces, each piece has the ability to regenerate into a fully formed individual. When decapitated, they retain their memories.
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.
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. In the United Kingdom, P. torva is a successful predator of the invasive New Zealand mud snail (Potamopyrgus jenkinsi).
Species The following species are recognised in the genus Planaria:
Planaria adhaerens Planaria albocingata Planaria barroisi Planaria bicingulata Planaria chulunginensis Planaria cincinata Planaria cinerea Planaria dagarensis Planaria debilis Planaria delineata Planaria dybouskyi Planaria flava Planaria fontana Planaria fuliginosa Planaria fuliginosus Planaria fulvifrons Planaria fuscomaculata Planaria gigas Planaria grubii Planaria ignorata Planaria incerta Planaria kempi Planaria lemani Planaria lucta Planaria luteola Planaria macrocephala Planaria maculata Planaria marmorosa Planaria melanocerca Planaria melanopunctata Planaria melanotorquis Planaria nesidensis Planaria onegensis Planaria punctatum Planaria rosea Planaria rothii Planaria sabussowi Planaria savignyi Planaria semifasciata Planaria simplex Planaria sinensis Planaria subflava Planaria torva Planaria tremellaris Planaria unionicola Planaria verrucosa Planaria wytegrensis Planaria zeylanica
Application of planaria in research Planaria's use as an ethical and cost-effective alternative to vertebrate testing makes it commonly used in toxicology, neuroscience, and pharmacology. Planaria’s simple nervous system, high sensitivity to environmental changes, low maintenance in laboratory settings and well-characterized genome make them particularly useful for studying chemical toxicity, wound healing, and neuro-regeneration. In pharmacology and neuroscience, planaria are used to study the effects of psychoactive compounds, including investigations into drug addiction and withdrawal responses. In drug delivery studies, they are sometimes used to assess the bio-compatibility and potential irritancy of pharmaceutical formulations Additionally, their ability to regenerate lost body parts also makes them a common model for stem cell research.
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.
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