Gladde schijfhoren Gyraulus parvus forma laevis (Say, 1817) herkenbaar aan pigmentatie

In the dune lake ‘Spartelmeer’, in the municipality of Bloemendaal (province of Noord-Holland), the Ash gyro Gyraulus parvus s.str. (Say, 1817) lives together with the native European Smooth ramshorn G. parvus forma laevis, formerly known as G. laevis (Alder, 1838). This forma shows a characteristic pattern in pigmentation of some organs, distinguishing it from the nominate form and other species within the genus in the Netherlands. Further research is needed on populations of G. parvus s.l. elswhere in Europe to confirm the general validity of this pigmentation trait. However, hybridization can blur this distinction between the formas.