This aquatic plant with a sub-Atlantic distribution is present in Northern and Central Italy and in Sicily. It grows in rapidly flowing, well oxygenated, meso-eutrophic freshwaters that are poor in calcium and are often subject to strong seasonal variations, from sea level to about 1200 m. The species is sporadic in the central belt of the Sardinian temporary ponds. The genus name derives from Greek and means 'beautiful hairs' alluding to the thin stems; the species name comes from the Latin 'hamulus' (small hook) and means 'with small hooks'. Flowering period: May to October.

Italian name(s): Callitriche arrotondata (Italia), Gamberaja arrotondata (Italia), Gamberaja calabrese (Italia), Gamberaja di Re Giuba (Italia).