New Zealand mudsnails (Potamopyrgus antipodarum) in Boulder Creek, Colorado: environmental factors associated with fecundity of a parthenogenic invader

Abstract

New Zealand mudsnails (Potamopyrgus antipodarum (Gray, 1853)) are non-native snails that are increasingly spreading in freshwater systems in North America. Most invasive populations are parthenogenic and threaten native freshwater diversity. We observed variability of P. antipodarum fecundity each month for 16 months at a recently invaded site in Boulder Creek, Colorado. We collected 100 snails each month and dissected them to count embryos in the brood sac. We used a general linear model analysis to examine water-quality variables as predictors of the monthly variability in P. antipodarum fecundity. After dissecting 1600 snails, we observed four male individuals (<1%), brood sizes ranging from 0 to 70 embryos per snail, reproductively mature females at 3.2 mm in length or greater, and a significant relationship between snail length and embryo counts (r2 = 0.38, p < 0.001). The model with the highest level of support for predicting variability in snail fecundity included water temperature, snail shell length, water hardness (calcium carbonate), and nutrient levels (total phosphate) (adjusted r2 = 0.53, p < 0.01). These variables may be important for snail growth and promote increased rates of reproduction in this parthenogenic, invasive snail. These results can further inform efforts to model geographic areas at high risk of P. antipodarum establishment and rapid demographic growth.

Adaptive phenotypic plasticity in a clonal invader

“…Our data suggest that shell size varies as a function of phenotypic plasticity. Like previous studies, we demonstrated a direct, positive association between size and fecundity in female P. antipodarum (McKenzie et al., ). Several environmental factors affected size or fecundity directly, but only two of these factors, flow and turbidity, had an effect on brood size in interaction with size.…”

“…Any embryos were then removed and the head of each snail placed back into 96% ethanol to be sent to LGC Genomics (http://www.lgcgroup.com) for DNA extraction, mtDNA sequencing, and SNP genotyping. We assumed that embryo counts were comparable across samples because all snails were collected during the summer months, the presumptive reproductive peak (McKenzie et al., ; Schreiber, Glaister, Quinn, & Lake, ). Because infection status (and male vs. female status) can affect shell shape and size in P. antipodarum (e.g., Lagrue et al., ; Levri et al., ), we also determined whether macroparasites were present in the body cavity.…”

Long-term population fluctuations of the exotic New Zealand mudsnail Potamopyrgus antipodarum and its introduced aporocotylid trematode in northwestern France

“…Females were reproductively mature at shell height from 2.5 to 3.0 mm, with up to 74 embryos in the largest females. These results are also consistent with observations for other introduced populations, which mature at size between 2.5 and 3.5 mm, and have maximum brood size ranging from 60 to 89 embryos (e.g., Strzelec & Serafinski, 1996;Gaino et al, 2008;McKenzie et al, 2013).…”

“…The lack of sexual reproduction is consistent with what is seen for introduced P. antipodarum from Europe, Australia, and America, where males are rare or completely absent (e.g., Wallace, 1978Wallace, , 1985Hughes, 1996;Schreiber et al, 1998;Gaino et al, 2008;McKenzie et al, 2013;Collado, 2014). increased from March to May in each year, and also increased with snail size, as previously demonstrated (e.g., Winterbourn, 1970;Gérard & Poullain, 2005;Gaino et al, 2008;McKenzie et al, 2013).…”

“…), both adult and newly recruited, growing P. antipodarum were present throughout the year, but without obvious, constrained periods where most recruitment occurred. In general, parthenogenetic forms of P. antipodarum produce offspring throughout the year, with seasonal fluctuations in reproductive output depending on the clonal population considered and environmental conditions such as temperature, hardness (dissolved calcium), phosphorus level, food availability, and population density (e.g., Winterbourn, 1970;Dussart, 1977;Dahl & Winter, 1993;Schreiber et al, 1998;Neiman, 2006Neiman, , 2013Tibbets et al, 2010;McKenzie et al, 2013). Females in Le Petit Hermitage had a higher fecundity in 2013 when population densities were low (from 12 to 48 snails sampled per month) than in 2002 and 2004 when densities were very high (from 1,623 to 2,993 snails per month), although no significant correlation was found between monthly embryo number per adult female and snail abundance.…”