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Limpets (Ferrissia)

Taxonomic group

Planorbidae: Ferrissia

Diagnostic features

Ferrissia (synonym Gundlachia) are small, limpet-shaped snails, often with semi-transparrent shells that are easily overlooked (if you don’t have a microscope). Small individuals have fragile shells, but with increasing size the shells become more thickened and coloured. The limpet shape is asymetrical but not as paua-shaped as the larger native limpet Latia.

Typical habitats

Ferrissia are most common in slow-flowing, weedy streams where they often attach to submerged plant surfaces. Some populations also occur on stony bottom streams.


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

Indicator value

  • Hard bottom: 3
  • Soft bottom: 2.4

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

Ferrissia can be abundant in farmland streams with moderate to poor water quality. They have been assigned tolerance values of 3 (hard bottom sites) and 2.4 (soft bottom sites).