COMPARATIVE ASSESSMENT OF THE RESPONSE TO THE FUNCTIONAL TEST- LOAD OF THE CARDIOVASCULAR SYSTEM OF UNIO TUMIDUS BIVALVE MOLLUSKS LIVING IN LAKES WITH DIFFERENT TROPHIC STATUS

The response of the cardiac system of the freshwater bivalve Unio tumidus to hypoxic and salt functional loads depending on the trophic status of its habitat was studied by measuring the heart rate (HR). Using the example of two of its populations inhabiting the littoral zone of the oligo-mesotrophic Lake Naroch and the eutrophic Lake Batorino (Republic of Belarus), it was shown that under both studied stress effects, the values of some HR indicators demonstrate a pronounced tendency to increase, others to decrease with an increase in the trophic state of the lake, and some remain unchanged. The identified features should be taken into account when using HR indicators to assess the ecotoxicological state of water bodies.