Cardiac Activity of Pontastacus leptodactylus (Decapoda) under Prolonged Exposure to High Salinity: on the Possibility of Using Freshwater Crayfish in Testing Brackish Waters

Abstract—In this study we analyze the characteristics of the cardiac activity of crayfish held on a long-term basis in an environment with high salinity (6.5‰) in order to find out the fundamental possibility of using them as bioindicators in bioelectronic systems for monitoring the quality of marine coastal waters under high anthropogenic load. Similar salinity values were noted for many bays of the Baltic Sea subregions, for example, the Tallinn and Bothnian bays, which are characterized by intense anthropogenic load. It is found that an increase in water salinity from 0 to 6.5‰ causes an initial short-term increase in heart rate (HR) by 30%. It has been shown that crayfish can not only successfully survive for 1 month in high salinity water, but also change the characteristics of cardiac activity to a small extent. Some features are revealed in crayfish in water with altered salinity. During exposure to saline solution, crayfish show a clear diurnal rhythm of cardiac activity. The rhythmicity of the heart rate disappears a few days before the molt in both fresh and salt water. This study makes it possible to come to a conclusion about the possibility of using freshwater crayfish in bioelectronic systems for the continuous monitoring of the functional state of representatives of the local biota and for identifying the biological effects of pollutants in both fresh and brackish water.