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

Abstract

In this study, we analyzed the characteristics of the cardiac activity of crayfish during long-term keeping of animals 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 sub-regions, for example, the Tallinn and Bothnian bays, which are characterized by intense anthropogenic load. It was found that an increase in water salinity from 0 to 6.5‰ caused 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 were revealed in crayfish in water with altered salinity. During exposure to saline solution, crayfish showed a clear diurnal rhythm of cardiac activity. The rhythmicity of the heart rate disappeared a few days before the molt in both fresh and salt water. The study made it possible to draw a conclusion about the possibility of using freshwater crayfish in bioelectronic systems for 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.