Summary
1) The behavioral thresholds ofApteronotus andEigenmannia to imposed sine wave electric fields were measured as a function of stimulus frequency using operant conditioning techniques. 2)Apteronotus responds to a broad range of frequencies. Its threshold—frequency curve is complex, showing three distinct threshold dips at: <5–15 Hz, 0.6–0.9 μV/cm; 200–300 Hz, 0.9 μV/cm; and 700–2200 Hz to 0.2 μV/cm. The high frequency dip itself is bimodal, with a primary minimum at the fish's electric organ discharge (EOD) fundamental, and a secondary minimum at its second harmonic. 3) The threshold—frequency curve forEigenmannia differs in several respects, being unimodal and sharpely tuned to the fish's EOD frequency with a sensitivity of 0.2–0.3 μV/cm.Eigenmannia shows a lack of keen low frequency perception, and no marked sensitivity increase at the second harmonic of its EOD. 4) The EOD wave forms ofApteronotus andEigenmannia were Fourier analysed:Eigenmannia's EOD approximates a sine wave, whileApteronotus' EOD contains considerable power at harmonic frequencies. 5) It is proposed that behavioral thresholds to frequencies within ca. 50–100 Hz of the fish's EOD fundamental or second harmonic are improved by the fish's extraction of, and preference for, low frequency beats of its EOD with the stimulus. This is suggested by the sharp, EOD specific tuning demonstrated by bothEigenmannia andApteronotus and the second harmonic sensitivity peak ofApteronotus, which are not predicted by known receptor response characteristics. Such a beat extraction capability might provide a mechanism for improving the resolution of conspecific electrocommunication. 6) The influence of water resistivity on the behavioral thresholds ofApteronotus was measured. High frequency sensitivity increases as a power function with decreasing water resistivity down to 1 k Ohm · cm, below which it remains constant. Low frequency sensitivity increases progressively from 100 k Ohm · cm down to 10 k Ohm · cm, but decreases again below this value. Thus low frequency eleotroreceptors are maximally sensitive in 10 k Ohm · cm water, while high frequency receptors function best in water below 1 k Ohm · cm.
Similar content being viewed by others
References
Bennett, M. V. L.: Mechanisms of electroreception. In: Lateral line detectors, Cahn, P., ed., p. 313–393. Bloomington: Indiana University Press 1967
Bennett, M. V. L.: Electroreception. In: Fish physiology, Hoar and Randall, eds., p. 493–574. New York: Academic Press 1971
Black-Cleworth, P.: The role of electrical discharges in the non-reproductive social behavior ofGymnotus carapo L. (Gymnotidae Pisces). Anim. Behav. Monog.31, 1–77 (1970)
Bullock, T. H.: Biological sensors. In: Vistas in science. Albuquerque: University New Mexico Press 1968
Bullock, T. H.: Species differences in effect of electroreceptor input on electric organ pacemakers and other aspects of behavior in electric fish. Brain, Behav. Evol.2, 85–118 (1969)
Bullock, T. H., Hamstra, R. H., Jr., Scheich, H.: The jamming avoidance response of high frequency electric fish. J. comp. Physiol.77, 1–48 (1972)
Caldwell, W. E., Germas, J. E.: An exploratory study of the environmental preferences of electric fish (Sternarchus albifrons). J. gener. Physiol.115, 33–39 (1969)
Granath, L. P., Sachs, H. G., Erskine, F. T.: Electrical sensitivity of a weakly electric fish. Life Sci.6, 2373–2377 (1967)
Hagiwara, S., Szabo, T., Enger, P. S.: Electroreceptor mechanisms in a high frequency weakly electric fish,Sternarchus albifrons. J. Neurophysiol.28, 784–799 (1965)
Heiligenberg, W.: Electrolocation of objects in the electric fishEigenmannia (Rhamphichthydiae, Gymnotoidei). J. comp. Physiol.87, 137–164 (1973)
Hopkins, C. D.: Patterns of electrical communication among gymnotid fish. Ph. D. Thesis, Rockefeller University, New York (1972)
Hopkins, C. D.: Lightning as background noise for communication among electric fish. Nature (Lond.)242, 268–270 (1973)
Kalmijn, A. J.: Bioelectric fields in sea water and the function of the ampullae of Lorenzini in elasmobranch fishes. S.I.O. Reference Series, 72–83 (1972)
Kalmijn, A. J.,: The role of electroreceptors in the animal's life. I. The detection of electric fields from inanimate and animate sources other than electric organs. In: Handbook of sensory physiology III, Fessard, A., ed. New York: Springer (in press)
Larimer, J. L., MacDonald, J. A.: Sensory feedback from electroreceptors to electromotor pacemaker centers in gymnotids. Amer. J. Physiol.214, 1253–1261 (1968)
Lissmann, H. W.: On the function and evolution of electric organs in fish. J. exp. Biol.35, 156–191 (1958)
Roth, A.: Zur Funktionsweise der Elektrorezeptoren in der Haut von Welsen (Ictalurus): Der Einfluß der Ionen im Süßwasser. Z. vergl. Physiol.75, 303–322 (1971)
Scheich, H., Bullock, T. H.: The role of electroreceptors in the animal's life. II. The detection of electric fields from electric organs. In: Handbook of sensory physiology III, Fessard, A., ed. New York: Springer (in press)
Scheich, H., Bullock, T. H., Hamstra, R. H., Jr.: Coding properties of two classes of afferent nerve fibers: high frequency electroreceptors in the electric fish,Eigenmannia. J. Neurophysiol.36, 39–60 (1973)
Storey, L. R. O.: An investigation of whistling atmospherics. Trans. roy. Soc.246, 113–141 (1953)
Szabo, T.: Specialized receptors in lower vertebrates. In: Handbook of sensory physiology III, Fessard, A., ed. New York: Springer (in press)
Author information
Authors and Affiliations
Additional information
The guidance of Drs. T. H. Bullock, C. D. Hopkins and A. J. Kalmijn is gratefully acknowledged. I wish to thank Drs. J. A. Bastian and W. F. Heiligenberg for their critical readings of the manuscript, and T. G. Uter for his technical assistance.
The work was supported by grants from the National Science Foundation, National Institute of Neurological Diseases and Stroke and the Sloan Foundation.
Rights and permissions
About this article
Cite this article
Knudsen, E.I. Behavioral thresholds to electric signals in high frequency electric fish. J. Comp. Physiol. 91, 333–353 (1974). https://doi.org/10.1007/BF00694465
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00694465