The effect of low temperatures on the defensive behavior of gastropods, on the example Helisoma duryi (Wetherby, 1879)

The study of the influence of ambient temperature on the behavior of poikilothermic animals is an important stage in understanding the mechanisms of regulation of nervous activity and adaptation processes. The work was carried out on the freshwater gastropod Helisoma duryi, which is a representative of the invasive fauna. The study of the defensive behavior of the mollusk was carried out by tactile stimulation of the tentacles using graduated nylon hairs with an impact force of 0.01N, 0.06N, and 0.001N. The dependence of the characteristics of defensive behavior when exposed to a hair of 0.001H on the duration of the stay of mollusks at low temperatures and the size of mollusks was experimentally established. It was found that smaller mollusks responded to irritation with two types of reactions - covering the body with a shell (73.3 %) and retraction of the tentacle (26.7 %). With the increase in the size of mollusks, the proportion of individuals responding to the effect of the hair by retraction of the tentacles increases, and individuals appear that ignore the effect. The study of defensive behavior at low temperatures was carried out at a temperature of + 4 °C and different exposure periods - 60, 120, 240, 360 minutes and 24 hours. It was shown that as the duration of exposure at a given temperature increased, the ratio of types of defensive reactions changed - the proportion of mollusks responding by pushing the shell (covering the body with a shell) increased, due to a decrease in the number of individuals responding to the stimulus by retraction of the tentacle and ignoring the effect. When the stimulus was presented to mollusks repeatedly 20 minutes after the first stimulus after cold exposure of different duration, it did not reveal statistically significant changes in the responses of mollusks in all variants of the experiment, except for 60 minutes of exposure. This confirms the profound functional rearrangements in the body of mollusks under the action of low temperatures.