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Bioelectric Sensing in Sharks and Rays

Bioelectric Sensing in Sharks and Rays. ENGN/BIOL 267. Behavior and Electrosensory Capability. http://www.youtube.com/watch?v=BPDu0TvUtAU http://dsc.discovery.com/videos/perfect-predators-shorts-white-tip-blind-killer.html http://www.youtube.com/watch?v=5JWvTFZZsAc.

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Bioelectric Sensing in Sharks and Rays

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  1. Bioelectric Sensing in Sharks and Rays ENGN/BIOL 267

  2. Behavior and Electrosensory Capability http://www.youtube.com/watch?v=BPDu0TvUtAU http://dsc.discovery.com/videos/perfect-predators-shorts-white-tip-blind-killer.html http://www.youtube.com/watch?v=5JWvTFZZsAc

  3. What sensory cues are important for predation? • Visual • Odors • Mechanical • Thermal • Salinity • Oxygen/Carbon Dioxide concentration • Electrical But how do we really know electrical signal helps sharks find their next meal???

  4. Plaice (weakly electric fish) sand

  5. Fish odors sand

  6. Fish odors sand

  7. Polyethylene film coated box: An “electric shield” sand

  8. So far we know… • Sharks don’t use visual sense to find plaice • Don’t use mechanical stimuli to find plaice • Suspect they use electrical sense, but not yet proved. In Kalmijn’s words: • “However, such an indirect conclusion may indicate only a limitation on the human imaginative faculty if not tested thoroughly and affirmed by more direct evidence.”

  9. The Big Question • “How do they do it? • What about their physiology endows it with such keen electrical sensing? • How can we apply physics principles to understand/model the system? • And, equipped with this knowledge, what we be inspired to build? • Glad you asked...Good thing we’re all in bioE!

  10. A bit of shark physiology

  11. Pores leading to “jelly-filled canals” on the Ray (raja natusa) and tiger shark Injected ink shows distribution of sensory canals. From Montgomery et al. Journal of Experimental Biology 202, 1349–1355 (1999)

  12. Electroreceptors in the Shark

  13. Ampullae of Lorenzini To epidermis/ocean water Ampullary canal: filled with Mucous-like, sugary gel Ampulla: Bulblike termination of canal Alveoli: individual “pouches” Receptor Cellsline bottom of ampulla. Electrical stimulus Neural signal Bv = blood vessel Mn = myelinated nerve From WaltmanActa Physiol. Scand. (1966) “The Fine Structure of Ampullary Canals of Lorenzini”

  14. Ampullae of Lorenzini Laminar section through canal wall Same, Zoomed IN 100 um Epithelial Cells form tight junctions

  15. Receptor Cell—Nerve Terminal Section through ampullary alveolus Receptor cell forms synapse Accessory cell: electrical insulation for receptor cells Receptor Cell Presynaptic ribbon: Connection coming from receptor cell  nerve terminal Nerve terminal: Path to sensory neuron Synapse formation

  16. Coding electricity in neural impulses/responses Subthreshold response Action potential A cartoon model of the receptor cell making synapse onto nerve. • * Receptor cells are electrically active! • Exhibit all-or-nothing response From Obara and Bennett: J Physiol (1972) “Mode of Operation of Ampullae of Lorenzini Skate, Raja

  17. Receptor cells at base of alveolus

  18. Full circuit model

  19. Current Divider Icanal Nrc ~20000 Iapex ~ Icanal

  20. Equivalent Circuit 20 kW 1.2 MW 12 kW Voltage drop across apical membrane is about 97.4% of Vin  Only 2.6% loss of signal strength!!

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