Opacuincola gretathunbergae

The sample of 20 collected had an average shell height of 2.35 mm and a height of 1.41 mm, and an aperture just under a millimetre wide. This species is closely related to Opacuincola ngatapuna, which has larger genitalia. Its well-developed eyes and pigmentation suggest it is a true crenobiont, one of a small number of species associated with freshwater springs, rather than dwelling in subterranean groundwater.

The snail was discovered in 2016 by a research team from the University of Greifswald, which spent two weeks surveying easily-accessible water bodies in the northern South Island, and discovered multiple new species of endemic snail. This species lives in small streams with shallow and slow-flowing water, and has so far been found in just one site. It was collected off stones and debris in a trickle of water beside Cobb Dam Road in the upper Tākaka River valley, within Kahurangi National Park.