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Guide to New Zealand's freshwater invertebrates
Planorbarius is an introduced snail with a shell coiled in a “planispiral” way that produces no obvious spire or pointed end. The shells are much larger and wider than those of our native planorbid Gyraulus. There is no operculum (protective shield) covering the aperture (shell opening) when the animal withdraws, and there is no keel around the outside of the shell.
Planorbarius is probably common in aquaria and ornamental ponds, but it has been recorded in the Waikato River, and in some lakes e.g. Lake Tarawera.
Like most snails they are grazers, scraping biofilms from submerged surfaces.
The presence of Planorbarius in the wild is probably an indication of a nearby ornamental pond that supports a population of this exotic snail. They have not been assigned any tolerance values.