Planaria is a genus of planarians in the family Planariidae. When an individual is cut into pieces, each piece has the ability to regenerate into a fully formed individual. 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 Uses of planaria in research Planaria has been widely used as a model invertebrate organism in pharmacological research, in particular in the studies of the drugs of abuse. Due to its excellent ability to regenerate, planaria has also been used as a model in regeneration studies. It was also proposed as a model in toxicological research. References Deochand, N., Costello, M. S., & Deochand, M. E. (2018). Behavioral Research with Planaria. Perspectives on behavior science, 41(2), 447–464. https://doi.org/10.1007/s40614-018-00176-w Continenticola Rhabditophora genera