On Galvanotropism and Oscillotaxis in Fish

HERMANN (1885) found that small fish (and fish embryos) and other animals such as tadpoles in a direct current (D.C.) field of a certain density, direct themselves parallel to the current lines, with their heads towards the anode (galvanotropism). On reversing the current all these animals turn 180 and the fish swim to the other electrode (galvanotaxis). This has been confirmed by Blasius & Schweizer (1893), Nagel (1894-5), Scheminzky (1924a) and others. When a fish is turned round in a field, so that it faces the cathode, it becomes excited and shows swimming movements and tremors of the body and tail. This occurs with normal as well as with spinal animals (Hermann, 1886; Hermann & Matthias, 1894). Destruction of the spinal cord abolishes all these phenomena. Several explanations have been given for galvanotropism. The earlier authors were of the opinion that the position parallel with the current lines, with the head towards the anode, is the location in which the animal is stimulated least, the fish having moved around until it got into this position (Hermann, 1886; Nagel, 1894-5). Loeb & Maxwell (1896) and Loeb & Garry (1896-7), who worked on crayfish and on Amblystoma, assume that the D.C. stimulates nerve cells having a certain position in the central nervous system (c.N.S.) and so causes an orientation of the animal, which makes movements towards the anode more easy, towards the cathode more difficult. Breuer (1905) observed, in fish held at right angles to the current lines in a D.c. field, a bending of the head and the tail towards the anode. This reaction was abolished by destruction of the spinal cord and is, according to him, caused by a stimulation of structures in the cord. He thinks that this reaction alone cannot explain the galvanotropism, but that the movement of the head towards the anode and the moving of the tail into a position parallel with the current lines is governed by the labyrinths. Scheminzky (19246) supports this view, as he could not demonstrate galvanotropism in trout embryos at an age at which the labyrinths were still undeveloped.