Potamopyrgus antipodarum J. E. Gray (New Zealand mudsnail)

Potamopyrgus antipodarum (synonymous with P. jenkinsi and Hydrobia jenkinsi) is a small, aquatic hydrobiid snail (Figures 19.1 and 19.2). In its native range the height of the shell can reach sizes of up to 12mm, but in the invaded range its adult size is generally 4-6mm (Ponder, 1988; Levri, et al, 2007). The shell is dextral and adults normally have five to six whorls. There can be great variation in the shell shape (from slender and elongate to ventricose) and shell ornamentation (with or without spines or keels) (Winterbourne, 1970). The shell colour ranges from light to dark brown, but encrusted shells may be other colours.