Resistance of freshwater gastropod mollusk Melanoides granifera to the effect of low temperatures

One of the current environmental problems is the spread of alien species of invertebrates, in particular representatives of tropical water bodies, in unusual environmental conditions. The values of the lower lethal temperature (NLT) for tropical gastropod freshwater mollusk Melanoides granifera as a representative of the invasive fauna were experimentally established. NLT was determined at two acclimation temperatures and different exposure times. When the acclimation temperature decreased, there was a decrease in the NLT value and the point of cold death. At 8-hours time of exposure to low temperatures and acclimation at a temperature of +20, the NLT value was + 8.4˚C, when acclimated to the water temperature +18 - + 7.3˚C. When the exposure time was increased to 168 hours at an acclimation temperature of + 20° C the NLT value was + 13.3 ° C. The study of the dynamics of survival of mollusks at low temperatures showed a natural increase in the percentage of death of individuals with increasing exposure time. However, it was found that they are able to maintain viability for 168 hours in a dried soil with a humidity of 20%. It was noted that during gradual drainage of the soil, mollusks are able to survive with a decrease in soil moisture up to 2%. It was shown that under the action of low temperatures, the probability of mollusk survival in the drying soil is higher than in the watered soil, which is probably due to their transition to a state of biological dormancy. The obtained results indicate that low ambient temperatures in the autumn-winter period can become the main factor limiting the invasion of Melanoides granifera into the natural water bodies of the Central Russia.