Abstract

Adult crabs Neohelice granulata were exposed for 96 h to 0.125 mg/L of parathion under complete submersion. Crabs were then exposed to air for 6 h (emersion period) to be finally re-submerged. Cardiac rate and ventilatory frequency, as well as hemolymphatic pH, pCO₂ and pO₂ were measured at different times throughout the experiment. Cardiac rate was significantly lower in crabs exposed to parathion, but only during the submersion periods, when cardiac activity is normally high. The insecticide could be affecting the neurological regulation of heart, avoiding the normal increase of cardiac activity. Ventilatory frequency, hemolymphatic, pH and gas parameters remained unaltered by exposure to 0.125 mg/L parathion, both under submersion and emersion.

Key words: Parathion, cardiac rate, crabs, submersion, emersion.