Snail (Glyptophysa)

Taxonomic group

Planorbidae: Glyptophysa

Diagnostic features

Glyptophysa (formerly Physastra) is a native snail genus that appears to have become increasingly rare over recent decades. They are similar in shape to the introduced Physa, but Glyptophysa has rings of nodules or shouldering around the edges of some whorls. As with Physa there is no operculum (protective shield) covering the aperture (shell opening) when the animal withdraws, and the aperture is on the left when facing toward you and when the spire points upwards.

[Glyptophysa]. Nodules and shouldering on whorls. Image: Stephen Moore Image — Glyptophysa. Nodules and shouldering on whorls. Image: Stephen Moore

[Glyptophysa]. Aperture is on the left when facing toward you and when the spire points upwards. Image: Stephen Moore Image — Glyptophysa. Aperture is on the left when facing toward you and when the spire points upwards. Image: Stephen Moore

Typical habitats

Glyptophysa tend to be found in wetlands or slow flowing streams amongst aquatic plants.

Feeding

Like most snails they are grazers, scraping biofilms from submerged surfaces.

Indicator value

Hard bottom: 5
Soft bottom: 0.3

The tolerance values (ranging from 0 to 10) give an indication of which are the sensitive taxa (values of 8 or more) and which are the tolerant taxa (values of 3 or less). For more information see: Indicator species

The presence of Glyptophysa is probably of more conservation interest than water quality interest. They have been assigned tolerance values of 5 (hard bottom sites) and 0.3 (soft bottom sites).