PERCEPTION OF WEAK ELECTRIC AC CURRENTS BY THE EUROPEAN EEL, ANGUILLA-ANGUILLA

1. 1. The European eel, Anguilla anguilla was conditioned to exhibit bradycardia to sine wave electric currents. 2. 2. Sensitivity to 0.5, 2. 5 and 50 Hz currents were tested in fresh water (resistivity 3 × 104Ω cm). Voltage gradient thresholds with the eel parallel to current direction averaged 0.97 mV/cm at 0.5 Hz, increasing to 19 mV/cm at 50 Hz. With fish perpendicular to the current, the corresponding thresholds were 3.6 and 59 mV/cm. 3. 3. With the eel oriented parallel to the current, current density thresholds averaged 0.031 μA/cm2 in fesh water, increasing to 0.88 μA/cm2 in brackish water (6.3 × 104Ωcm) at 0.5 Hz. Corresponding voltage gradients are approx 1 mV/cm irrespective of resistivity. 4. 4. The anterior half of the eels were 4-5 times more sensitive than the posterior half. © 1979.