Variation in minimum temperature tolerance of two invasive snails in central Texas, USA
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Invasive species are a major concern for aquatic ecosystems and tropical freshwater snails (Thiaridae) can be very successful invaders. Melanoides tuberculata and Tarebia granifera are two invasive snails in Central Texas that serve as intermediate hosts for several Asiatic trematode parasites of fishes, birds, and other organisms including domestic animals and humans. A better understanding of their temperature tolerances is needed to better predict their spread in Texas and to inform management strategies. Therefore, the goal of my study was to determine the critical thermal minimum of these species and to compare temperature tolerances between species, rivers, and different local morphotype. Survival of snails were monitored in environmental tanks in which temperature was decreased by 0.1°C per hour from 23°C to 10°C. In addition, survival was monitored over time in environmental tanks in which temperature was held constant at 17°C, 15°C, 11°C and 10°C after acclimatization. Temperature tolerances differed significantly between snails from different rivers or river segments. There was no significant difference in survival at colder temperatures between M. tuberculata and T. granifera, nor between local morphotypes of M. tuberculata found in Central Texas. My results show that M. tuberculata can tolerate colder temperatures down to 11ºC for a few weeks, which will facilitate their dispersal in rivers of Central Texas farther away from thermally stable spring influenced reaches. Future research should examine differences in temperature tolerances between rivers in central Texas and further examine potential role of local adaptation of M. tuberculata.