Cardiac activity of crayfish Cherax quadricarinatus (Von Martens 1868) in different physiological states

Diurnal cardiac rhythm of crayfish Cherax quadricarinatus was studied. Crayfish were contained in laboratory conditions with the following illumination mode: 12 hours of light, 12 hours of darkness. Real-time heart rate was recorded non-invasively for several months using the original fiber-optic method. It was stated that after a certain period of acclimation a pronounced diurnal rhythm was established in crayfish. It changes during the pre-molting stage of the molting cycle and disappears completely within 3-5 days immediately preceding molting. It was shown that changes in the chronotropic characteristics of cardiac activity such as cardiac rhythm found in these experimental conditions could serve as reliable criteria for the assessment of the functional state of the crayfish, which is used as a test-organism for the assessment of surface waters ecological state.