Life history and ecology of Potamopyrgus estuarinus (Gastropoda: Tateidae) in the tidal reaches of two New Zealand rivers

ABSTRACT

Aspects of the life history and population structure of the common mud snail Potamopyrgus estuarinus were investigated at tidally-influenced sites in the vicinity of Christchurch, New Zealand. Many snails are alternately exposed to air and submerged in water on tidal cycles and are subject to a highly variable and often rapidly changing temperature regime. Annual air temperature ranged from 0.5–39 °C within the tidal reaches of the study areas. The organically enriched Heathcote River populations were dominated by large individuals during all months, whereas in the rural Taranaki Stream, high proportions of small and large snails were present on most sampling occasions. Population density at the latter site averaged about 16,000 m⁻² and was highest in winter. Although growth could not be inferred from size frequency data, laboratory rearing of snails indicated that individuals would reach full size in less than a year. Mature snails at all sites were primarily females (mean ratio 1.4:1). The egg of P. estuarinus is described and the incidence of trematode larvae, principally metacercarial cysts of an unidentified species, is reported.

KEYWORDS:

• Growth
• metacercariae
• parasitism
• population structure
• sex ratio
• temperature environment

Acknowledgements

I thank the Freshwater Ecology Research Group, School of Biological Sciences, University of Canterbury, for access to laboratory facilities. Ryan Hechinger provided helpful advice on the dissection and identification of metacercarial cysts, and useful comments on the manuscript were made by Winston Ponder and two referees.

Disclosure statement

No potential conflict of interest was reported by the author.