Abstract
The acoustic near field of quietly moving underwater objects and the bio-electric field of aquatic animals exhibit great similarity, as both are predominantly governed by Laplace's equation. The acoustic and electrical sensory modalities thus may, in directing fishes to their prey, employ analogous processing algorithms, suggesting a common evolutionary design, founded on the salient physical features shared by the respective stimulus fields. Sharks and rays are capable of orientating to the earth's magnetic field and, hence, have a magnetic sense. The electromagnetic theory of orientation offers strong arguments for the animals using the electric fields induced by ocean currents and by their own motions in the earth's magnetic field. In the animal's frame of reference, in which the sense organs are at rest, the classical concept of motional electricity must be interpreted in relativistic terms. In the ampullae of Lorenzini, weak electric fields cause the ciliated apical receptor-cell membranes to produce graded, negative receptor currents opposite in direction to the fields applied. The observed currents form part of a positive-feedback mechanism, supporting the generation of receptor potentials much larger than the input signal. Acting across the basal cell membranes, the receptor potentials control the process of synaptic transmission.
Full Text
The Full Text of this article is available as a PDF (940.1 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Kalmijn A. J. Electric and magnetic field detection in elasmobranch fishes. Science. 1982 Nov 26;218(4575):916–918. doi: 10.1126/science.7134985. [DOI] [PubMed] [Google Scholar]
- Kalmijn A. J. Electric and near-field acoustic detection, a comparative study. Acta Physiol Scand Suppl. 1997;638:25–38. [PubMed] [Google Scholar]
- Kalmijn A. J. The electric sense of sharks and rays. J Exp Biol. 1971 Oct;55(2):371–383. doi: 10.1242/jeb.55.2.371. [DOI] [PubMed] [Google Scholar]