Plectus parvus is a species of nematode (roundworm) found in freshwater and terrestrial environments.
[1] Along with the similar nematode Panagrolaimus detritophagus, in 2018 it was the first species of multicellular eukaryote to be thawed into a living state after prolonged cryopreservation.
The names Plectus potamogeti (Schneider, 1937) and Rhabdolaimus baltonicus (Daaday, 1894) are considered synonyms.
[6] In the river sediments and soils it inhabits, this worm is part of the benthos group.
[1] It has been shown that interaction between this species and another soil nematode Bursilla monhysteria in damp podzols increases both bacterial biomass and nitrogen mineralisation.