DOI: 10.3391/ai.2025.20.2.150239

Authors: Nicholas T. Lewis, Sarah R. Goodnight, Daya Hall-Stratton, Amy E. Fowler

Abstract: Freshwater Japanese mystery snails (Cipangopaludina japonica, previously Heterogen japonica) were introduced to North America from Asia in the early 1900s and have colonized many lake and river systems across the United States (US). Tolerance to environmental stressors, such as desiccation, plays a large role in species’ invasion potential and persistence in novel environments. To characterize the desiccation tolerance of C. japonica snails, adults and juveniles from three eastern US populations were exposed to air for 13.5 weeks (adults, n = 650) or 48 hours (juveniles, n = 849) and their mortality assessed over time. Over 50% of adult snails from each population exposed to desiccation survived over 10 weeks of constant air exposure, while survival ranged from 10 to 64% at the end of the exposure experiment (13.5 weeks), depending on population, indicating exceedingly high resistance to desiccation mortality in adults of this species. In contrast, juvenile snails were much more vulnerable to desiccation, with over 70% mortality at just 24 hours of drying and only a single individual surviving 48 hours of desiccation stress. We found that the interaction between snail shell length and time affected survival for both adults and juveniles, where larger body sizes were associated with increased probability of survival as time of exposure increased (p < 0.001 for both juveniles and adults). Based on these data, juveniles cannot survive long-term air exposure, but the high desiccation tolerance of adults may facilitate survival and population persistence in stressful environments and allow for increased dispersal between water bodies. Therefore, both commercial and recreational users of water bodies containing introduced C. japonica should be aware of the risk of unintentional dispersal between water bodies via contaminated gear and/or boats, even if those materials are exposed to air for a significant amount of time.

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DOI: 10.3391/ai.2023.18.2.104203

Authors: Pratyush Jaishanker, Daya Hall-Stratton, Amy E. Fowler

Abstract: The freshwater Japanese mystery snail (Heterogen japonica) was introduced to the United States in the early 1900s and has since established populations throughout the continent. The species has ovoviviparous reproduction (i.e., eggs hatch within the mother and develop inside before being released as juveniles), which is one reason it has been successful. Despite its wide geographic range, little is known about its physiological tolerances. For example, high salinities and temperatures may limit its spread, and determining the species’ tolerance to these environmental factors is crucial to predict its possible range expansion. To test this, 600 juvenile H. japonica (average shell length: 6.0mm, range: 4.5–8.3mm) were collected from 28 females from a lake in Virginia, USA and placed in a fully crossed design to test the interaction between salinity (0.2 and 2 PSU) and temperature (25 °C, 34 °C and 38 °C). Juveniles were monitored for mortality over two weeks. Kaplan–Meier survival analyses determined median survival probabilities, and generalized linear models compared differences in mean survival. All juveniles in 25 °C (except one in 0.2 PSU) survived (N=199/200), and all juveniles in 38 °C died by the end of 14 days (N=200), irrespective of salinity. However, juveniles kept at 38 °C showed higher early (≤4 days) mortality in 0.2 PSU, but lower early mortality in 2 PSU. Importantly, juveniles in 2 PSU survived for ≥2 days (N=294/300) across all temperatures, indicating that there may be scope for expansion through estuaries. Future work should examine temperatures between 34 and 38 °C and salinities above 2 PSU to understand the extent of covariance between salinity and temperature and create mathematical models to estimate survivability and spread.

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