28th ANNUAL EASTERN FISH HEALTH WORKSHOP April 21-25, 2003 Thermal Limits Of Red-Rimmed Melania Melanoides tubercuata, (Gastropoda: Prosobranchia: Thiaridae): Implications For Control And Distribution Of A Snail That Vectors A Gill Trematode Causing Serious Infections In Fish Andrew J. Mitchell1 and Thomas M. Brandt2 1 Harry K. Dupree-Stuttgart National Aquacutlure Research Center, United States Department of Agriculture, Agriculture Research Service, P. O. Box 1050, Stuttgart, Arkansas, 72160; 2United States Fish and Wildlife Sservice, NFHTC, 500 East McCarty Lane, San Marcos, TX, 78666 The red-rimmed melania Melanoides tuberculata, an Asian aquatic tropical snail of the family Thiaridae, is spreading across Mexico, the southern United States and through geothermal waters in several mid western and northwestern states.  In addition to its potential to displace native mollusks, it harbors several parasites including Centrocestus formosanus, a gill trematode that has caused serious infections in cultured fish in Florida and in wild fish stocks in Texas.  The red-rimmed melania is resistant to drying and to a number of molluscicides and disinfectants used to prevent its spread.  Temperature tolerances for the red-rimmed melania were examined to allow predictions to be made on its spread from current known U.S. locations.  Also, the potential of using hot water to disinfect nets and collecting equipment to prevent the spread of this parthenogenetic snail from contaminated to uncontaminated waters was investigated.      To test the effect of temperature on red-rimmed melania survival, three or six replicated groups of 10 snails (10 to 25 mm in length) were placed into incubation chambers and water baths that were set at nine temperatures (5 to 45°C) for 24 different exposure periods (2 min to 27 d).  In addition, snails were grouped in four size classes (1-4, 18-22, 28-32, and 38-42 mm) and were subjected to 50°C for 0.25 to 3 min.  Water temperatures of 5°C for 1 d, 9°C for 4 d, 11°C for 8 d, 13°C for 12 d, 40°C for 10 h, and 45°C for 16 min were lethal to all snails.  At 50°C, all four sizes of snails succumbed within 2.5 min, with the smallest (1 to 4 mm) lasting less than 0.5 min.  Areas where temperatures drop below 15°C or exceed 35°C for 30 or more consecutive days a year probably will not support viable red-rimmed melania populations.  A 5-min exposure to 50°C water (household hot water temperature) should be sufficient to kill all red-rimmed melania on dip nets and other fisheries equipment. Return to 28th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page