Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Guide to New Zealand's freshwater invertebrates

Snail ( Melanopsidae : Zemelanopsis )

Diagnostic features

Zemelanopsis (formerly Melanopsis) is a native snail that is usually found in estuaries or in streams near the coast. They are bullet-shaped, with strongly built, olive green or brown shells. They have an operculum (protective shield) covering the aperture (shell opening) when the animal withdraws, and the aperture is on the right when facing toward you and when the spire points upwards (see lower photo).

Typical habitats

Zemelanopsis are usually found on stony streambeds in coastal streams and rivers, either within the seawater zone or a short distance upstream.


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

Indicator value

Zemelanopsis occur in the lower reaches of streams and rivers, including those with largely farmland catchments and dubious water quality. They have been assigned tolerance values of 3 (hard bottom sites) and 1.9 (soft bottom sites).