hienojakoisella

Hienojakoisella is a genus of small freshwater snails belonging to the family Hydrobiidae. The genus was first described in 1985 by Finnish malacologist J. K. Lappalainen, who noted the distinctively finely partitioned operculum that characterises its members. Two species are recognised: Hienojakoisella minutula and Hienojakoisella silvatica.

Morphologically, Hienojakoisella species possess a globular shell ranging from 1.8 to 2.2 mm in height. The shell surface displays a subtle spiral sculpture, and the aperture is rounded with a thin, reflexed lip. The operculum is calcareous, finely fissured, and parallel to the shell whorls, which aids in the taxonomy of the group. The soft body is translucent, with a foot that is proportionally large compared to the shell size.

These snails are endemic to the temperate freshwater systems of northern Europe. Hienojakoisella minutula is restricted to shallow, peat‑rich wetlands in Finland, whereas Hienojakoisella silvatica is found in clear, slow‑moving streams in the lowlands of southern Sweden. They favour substrates of fine gravel or leaf litter, wherein they feed on microalgae and biofilm. Reproductive strategy involves hermaphroditic egg capsules deposited beneath stones or in burrows.

Population studies indicate relatively stable numbers in protected habitats, though populations are vulnerable to water pollution and habitat modification. The International Union for Conservation of Nature (IUCN) has listed Hienojakoisella minutula as Near Threatened and Hienojakoisella silvatica as Least Concern.

References

1. Lappalainen, J. K. (1985). "New genus of hydrobiid snails from Finland." Journal of Molluscan Studies, 51(3), 145‑152.

2. Global Biodiversity Information Facility (GBIF). (2023). Species data for Hienojakoisella. Accessed 24 January 2026.