Hypania invalida (Grube, 1860) (Annelida: Polychaeta) is a Ponto-Caspian species. It is considered as eurytopic, active filter feeding and deposit feeding species (Manoleli 1975), with a preference for fine substrate, ranging from silt to gravel (Manoleli 1975; Popescu-Marinescu 1980; Rusev and Marinov 1964; Šporka 1998).

Hypania invalida is such an invasive species of the Ponto Caspian origin which, until now, has been the only polychaete inhabiting inland waters of Central Europe (Norf et al., 2010). Over the last 35 years, it spread widely and rapidly in Europe through the Volga, Dnieper, and Danube catchments

Ecology: Hypania invalida is one of few polychaete species (<2%) able to inhabit freshwater. In its native range, it exists in fresh and brackish water, tolerating a wide range of salinity (0–12 ppt), temperature (2-25°C), and depth (from shoreline up to 960 m) (Zenkevich 1963; Mordukhai-Boltovskoi 1964).

Hypania invalida este un vierme inelat din clasa polichetelor, de culoare portocalie-roșiatică. Corpul viermelui este cilindric, format din cap, trunchi și pigidium. Majoritatea celor 16 segemente toracice, cu excepția primelor două, poartă câte 20-24 de cheți în fiecare evantai.

The polychaete Hypania invalida (Grube, 1860) lives mainly in freshwater, but still has a high tolerance to salinity (0–12 PSU) and temperature (2–25 °C) (Mordukhai-Boltovskoi 1964). Hypania invalida has separate sexes with no evidence of a distinct sexual mode and has several life stages, one of which is a planktonic larva (Norf et al. 2010).