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Journal of Comparative Physiology A

, Volume 191, Issue 2, pp 115–123 | Cite as

Infrastructure in the electric sense: admittance data from shark hydrogels

  • Brandon R. Brown
  • Mary E. Hughes
  • Clementina Russo
Original Paper

Abstract

Elasmobranchs (sharks, skates, and rays) possess an electrosensory system with an infrastructure of canals connecting the electrosensors to the environment. The electrosensors and canals are filled with a uniform hydrogel, but the gel’s function has not yet been determined. We present electrical admittance spectra collected from the hydrogel from 0.05 to 100 kHz, covering the effective range of the electrosensors. We have taken samples of this gel, postmortem, from Triaenodon obesus and Carcharodon carcharias; for purposes of comparison, we have synthesized a series of collagen-based hydrogel samples. The shark hydrogels demonstrate suppressed admittance when compared to both seawater and collagen gels. In particular, collagen hydrogels with equivalent ion concentrations are roughly 2.5 times more polarizable than the shark samples. We conclude that the shark hydrogels strongly localize ionic species, and we discuss the implications for the related roles of the gel and the canals in the electric sense. The gel-filled canals appear better suited to fostering voltage differences along their length than to providing direct electrical contact to the seawater environment.

Keywords

Electrosensory Morphology Neurophysiology Elasmobranch 

Notes

Acknowledgements

This work was supported in part by a grant from the Fletcher Jones Foundation, and by the NSF via grant CHE-0216617. Access to specimens was provided by Pat Morales and Chris Doller of the Steinhart Aquarium at the San Francisco Academy of Sciences and by Sean Van Sommeran of the Pelagic Shark Research Foundation. We thank C.P. Hutchison for technical assistance and advice. We also thank Marcelo Camperi and Tim Tricas for fruitful discussions. These experiments comply with the “Principles of Animal Care,” NIH publication no. 86–23, and with US federal regulations.

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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Brandon R. Brown
    • 1
  • Mary E. Hughes
    • 2
  • Clementina Russo
    • 1
  1. 1.Department of PhysicsUniversity of San FranciscoSan FranciscoUSA
  2. 2.Division of Engineering and Applied SciencesHarvard UniversityCambridgeUSA

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