Cation-Mediated Orientation of Nematodes Under Electrical Fields

Abstract

The larvae of the wheat nematode Anguina tritici, released between platinum electrodes at 0.06 mA of current for 30 min in sand media saturated with tap water, migrated to the cathode. Similar migration to the cathode occurred in solutions of FeCl3 at 2 X 10 -3 to 4 X 10 -3 g lit. -1 , CoCl 2 , NiCl 2 , MnCl 2 , CrCl 3 , ZnCl 2 and BaCl 2 at 2 ×10 -3 to 6 X 10 -3 g lit. -1 , NaCl and KCl at 6 X 10 -3 tot 8 X 10 -3 g lit. -1 . Orientation was lost when a uniform magnetic field of 750 Oe was applied in a direction perpendicular to the electrical field in ferro- and para-magnetic salt solutions having high magnetic susceptibilities. The charges of the cations at concentrations that elicited maximum galvanotactic response were almost similar ranging from 2.33 X 10 -3 to 3.14 X 10 -3 Faradays/1. of the solutions for all the nine salts tested. It is concluded that the affinity for the cathode in nematodes depends on the density of cations in water and also on the amount of charge carried by the cations. It is suggested that the amphids of nematodes contain large negatively charged organic molecules of low water solubility that attract cations in water. The nematodes may sense the potential change resulting from any disturbance of the ionic atmosphere of the anionic amphidial molecules under an applied electrical field.