The ampullae of Lorenzini in the magnetic field

Abstract

1. The impulse activity of single nerve fibers supplying the ampullae of Lorenzini in hyoid group of the Black Sea skate, was recorded to study the response of these receptors to various modifications of stimulation with the vertical component of a magnetic field. 2. When the animal was at rest in motionless water an impulse reaction was observed only with changes in magnetic field, a constant field had no effect. The intensity of response was determined by the rate of magnetic field change (dB/dt). 3. The nature of responses to magnetic field changes depended on the orientation of the ampullary canals relative to induced currents in the animal's body and in the surrounding sea water (Figs. 1, 2 and 3). 4. The intensity of response of a single receptor to magnetic field changes decreased with the shortening of the ampullary canal under study (Fig. 4); cutting of the other canals or dissection of the capsule of the ampullary cluster appeared to have no effect. 5. The receptors of the ampullae of Lorenzini were shown to respond to a constant magnetic field when the fish moved in water, or when water was moved with respect to the fish (Figs. 5 and 6). 6. The character of impulse responses to a constant magnetic field depended on the direction of the field and the direction of movement of either the fish or the water. The relationship between the response intensity and magnetic field, or velocity of water flow is roughly linear (Figs. 7 and 8). 7. Symmetrical receptors on the right and left sides of the animal's body responded oppositely to stimulation by either increasing or constant magnetic field (Figs. 1 and 6). 8. Experiments involving compensation for the Earth's magnetic field with Helmholtz coils revealed a statistically significant reaction to the vertical component of the geomagnetic field (0.35 Gs in the region of the Karadag Biological Station, the Crimea). 9. The mechanisms and functional role of the detection of changing and constant magnetic field by the ampullae of Lorenzini are discussed.