We studied population density, population size, and reproductive seasonality of the Phantom Tryonia, Tryonia cheatumi (Pilsbry, 1935). This endangered freshwater snail is found only in the San Solomon Spring system, a cienega, or karst-based, arid-land freshwater spring system, in western Texas, USA. We sampled populations at seven locations in the system seasonally over a 2-yr period. San Solomon Spring, the system's largest spring and modified into a swimming pool, had the largest population of T. cheatumi, with an estimated 49 million individuals and a mean density as high as 23,626 ± 39,030 (individuals/m2 ± SD). There were seasonal differences in mean density (up to 25-fold) and median snail size at all sites, but consistent seasonal patterns of mean density or size were not observed. Median snail size among samples was not related to water temperature, and juveniles were present in most samples in all seasons. These results support continuous, aseasonal reproduction, as expected in thermally stable habitats, but differences in median size and mean density among seasons and sites suggest that other factors affect reproduction and seasonal variation in population size of T. cheatumi.
Kathryn E. Perez, Nina Noreika, Chad Norris, Marty Kelly, Melissa Lopez, Christina Ortega, Salma Ruiz Sandoval, Samantha Gonzalez, and Weston Nowlin "Population Density and Reproductive Seasonality of Tryonia cheatumi (Gastropoda: Cochliopidae), the Phantom Tryonia," Freshwater Mollusk Biology and Conservation 25(2), 82-90, (1 November 2022). https://doi.org/10.31931/fmbc-d-20-00006
Freshwater Mollusk Biology and Conservation