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A new electroreceptive teleost:Xenomystus nigri (Osteoglossiformes: Notopteridae)

Summary

The African knife fish,Xenomystus nigri, is found to be sensitive to weak electric fields by the method of averaged evoked potentials from the brain. Slow waves and spikes were recorded in or near the lateral line area of the medulla and the torus semicircularis of the mesencephalon in response to long pulses (best > 50 ms) and low frequency sine waves (best ca. 10 Hz) of voltage gradients down to < 10 μV/cm. Evoked waves in the lateral line area are a sequence of negative and positive deflections beginning with a first peak at ca. 24 ms; in the torus semicircularis the first peak is at ca. 37 ms. Spikes are most likely in the torus between 50 and 80 ms after ON. At each recording locus there is a best axis of the homogeneous electric field and a better polarity. Effects of stimulus intensity, duration and repetition are described. The physiological properties are similar to those of ampullary receptor systems in mormyriforms, gymnotiforms and siluriforms.

Confirming Braford (1982),Xenomystus has a large medullary nucleus resembling the nucleus otherwise peculiar to mormyriforms, gymnotiforms and siluriforms and now called the electrosensory lateral line lobe (ELLL; formerly the posterior lateral line lobe). We describe the projections of anterior and posterior lateral line nerves by HRP applied to the proximal stump of a cut nerve. A descending central ramus of the anterior lateral line nerve and a lateral component of the ascending ramus of the posterior lateral line nerve end in part in the ELLL.

Electroreception, including the system of discrete central structures mediating it, is for the first time found to be less than an ordinal or even a family character, but apparently a characteristic of the subfamily Xenomystinae. Species of the other subfamily, Notopterinae as well as of the other families of osteoglossiforms (Osteoglossidae, Hiodontidae and Pantodontidae), lack the ELLL.Notopterus andPantodon are found to lack the evoked potential.

The positive finding of evoked activity to feeble electric field is found to be the most practical method for searching widely among fishes for the presence of the electrosense modality and its central pathways. The anatomical criterion of an ELLL can now be taken to be a good criterion for the presence of this sensory system. The absence of evoked response correlates well with the absence of an ELLL.

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Similar content being viewed by others Explore related subjectsDiscover the latest articles and news from researchers in related subjects, suggested using machine learning. Abbreviations
ELLL :

electrosensory lateral line lobe

HRP :

horseradish peroxidase

TS :

torus semicircularis

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Author information Authors and Affiliations
  1. Neurobiology Unit, Scripps Institution of Oceanography and Department of Neurosciences, School of Medicine, University of California, 92093, San Diego, La Jolla, California, USA

    Theodore H. Bullock

  2. Division of Biological Sciences, The University of Michigan, 48109, Ann Arbor, Michigan, USA

    R. Glenn Northcutt

Authors
  1. Theodore H. Bullock
  2. R. Glenn Northcutt
About this article Cite this article

Bullock, T.H., Northcutt, R.G. A new electroreceptive teleost:Xenomystus nigri (Osteoglossiformes: Notopteridae). J. Comp. Physiol. 148, 345–352 (1982). https://doi.org/10.1007/BF00679019

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