Temperature Tolerance of Red‐Rim Melania Melanoides tuberculatus, an Exotic Aquatic Snail Established in the United States

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Abstract
The red‐rim melania Melanoides tuberculatus (family Thiaridae), a tropical, nonindigenous aquatic snail, has become established and is spreading in the United States. Concerns associated with the spread of this snail include its potential to displace native snail populations and to transmit trematodes. Of particular concern is the gill trematode Centrocestus formosanus now found in U.S. commercial and wild fish stocks. The snail survives year‐round in subtropical ponds and constant‐temperature spring runs in Florida and Texas and in geothermal waters of several western and midwestern states. Knowledge of the temperature tolerances of the snail will increase the ability to predict its potential range in North American waters and to control its spread. Under constant temperature conditions in the laboratory, all red‐rim melania (15–25 mm shell height (SH)) were killed by exposure to 5°C for 1 d, 9°C for 2 d, 11°C for 8 d, and 13°C for 12 d. At 17°C and 32.5°C, about 10% of the snails died within 27 d, indicating the outer limits of the temperature range for the snail. Waters that attain temperatures less than 18°C or greater than 32°C will probably not support red‐rim melania. All snails (10–20 mm SH) died within 10 h at 40°C and within 20 min at 45°C. At 50°C, all snails (≤42 mm SH) succumbed within 2.5 min, and the smallest snails (1–4 mm SH) survived for less than 0.5 min. A 4–5‐min exposure to 50°C or warmer water should kill all red‐rim melania on dip nets and other fisheries equipment.