EVALUATION OF MERCURY-INDUCED CHANGES IN CIRCADIAN HEART RARE RHYTHMSIN THE FRESH-WATER CRAB, POTAMON POTAMIOS AND THE CRAYFISH, ASTACUS-ASTACUS AS AN EARLY PREDICTOR OF MORTALITY

The influence of mercury on the expression of circadian rhythmicity in heart rate was investigated in the freshwater crab, Potamon potamios and the crayfish, Astacus astacus. This was made possible by the use o f an on-line, computer aided physiological monitoring (CAPMON) system. The effects of Hg2+ on light driven (12:12 hr light:dark regimen) cir cadian rhythmicity in heart rate were examined. In both Potamon potami os and Astacus astacus, exposure to HgCl2 was almost invariably associ ated with increased heart rate during daytime to levels similar to tho se at night. Rhythmicity was lost and death ensued in the following ho urs or days. This response was largely independent of exposure time an d mercury concentrations. In those: individuals that survived mercury exposure little or no change in the degree of circadian rhythmicity in heart rate was detected. Thus, loss in circadian rhythmicity of heart rate can be utilised as an early indicator for mercury toxicity. Copy right (C) 1996 Elsevier Science Inc.