2012/01/01 by Joseph R. Holomuzki, Holomuzki, Joseph R., Barry J. F. Biggs +1
Environmental Science · #Aquatic Invertebrate Ecology and Behavior #Fish Ecology and Management Studies #Parasite Biology and Host Interactions
paper · pdf · doi:10.26021/414
openalex publication_date 2012/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/01
Novel or highly effective antipredator traits can facilitate successful invasions by prey species. Previous studies have documented that both the native New Zealand snail, Potamopyrgus antipodarum, and the highly successful, worldwide invader Physella (Physa) acuta, seek benthic cover to avoid fish predators. We asked whether an invasive, South Island population of Physella has maintained this avoidance response, and if so, how it compared to that of Potamopyrgus that has coevolved with native fish. We compared patterns of sediment surface and subsurface use between snail species and between sizes of conspecifics both in a 2nd –order reach with predatory fish and in a laboratory experiment where fish presence (common bullies [ Gobiomorphus cotidianus]) was manipulated. Both snails sought protective sediment subsurfaces when with bullies. Proportionally, sediment subsurface use both in field collections and in fish treatments in the experiment were similar between species. Field-captured bullies ate more Physella than Potamoprygus, suggesting different consumptive risks, but overall, few snails were consumed. Instream densities and sizes (shell length) of Physella were greatest on cobbles, where most (>90%) egg masses were found. Potamopyrgus densities were evenly distributed across sand, gravel, and cobbles. Shell lengths were similar between snails on sediment subsurfaces and surfaces during daylight for both species, suggesting this avoidance response was not size-dependent. For Physella, retaining the ability to seek benthic refugia when exposed to novel predators likely greatly contributes to its invasion success. Given both snails are dominant primary consumers in many freshwater ecosystems, surface-density increases resulting from predation pressure decreases would predictably significantly affect system trophic dynamics.