Biological Electric FieldsBiological Electric FieldsDr. Joe E. MeiselDr. Joe E. Meiselbiological electrical fieldsbiological electrical fieldselectrical fieldmagnetic fieldvisible and IR spectrumdetection (electroreception,magnetoreception)vs. production (electrogenesis)all organisms produce electrical fieldsall organisms produce electrical fieldsnerve signalsmuscle contractionsmembrane potentialsanimal sensory apparatianimal sensory apparativisible lightIR - viper pits, Haller’s organsound waveschemicalgravityelectromagnetic fields ...electroreception in animalselectroreception in animalsdetection favored when other stimuli absentimagine a deep sea environment ...electroreception in animalselectroreception in animalsdetection favored when other stimuli absentimagine a turbid tropical river ...electrosensory perceptionelectrosensory perceptiondetect environmental objectsdetect conspecifics, prey, predatorscommunicatefrequency jamming, overlap, shiftingpassive vs. active techniquesElasmobranchs Elasmobranchs --Sharks, Skates & RaysSharks, Skates & RaysAmpullae of Lorenzini5-20 nV/cmdetect preyrays feed in sedimentoceanic cablessharks attacks electric fieldsharks attacks electric fieldPaddlefish (Polyodontidae)Paddlefish (Polyodontidae)USA freshwater systems (murky)detects metal, not plastic, objectsattacked wires with 10 nV currentrostrum w/ >40,000 ampullary sensorsdetect planktonic preyPaddlefish (Polyodontidae)Paddlefish (Polyodontidae)Monotremes Monotremes --Platypus & EchidnaPlatypus & Echidnaprimitive, non-placental mammalsnocturnal feeder, thick sedimentattack buried batteriesbill w/ mucous-gland electroreceptors300-2000 μV/cmElectric Eels, CatfishElectric Eels, Catfisheel (Electrophorus electricus) technically a “knifefish”murky freshwatermost feared fish in Amazonscattered ampullae & tuberous receptors13 μV/cm sensitivitysensory -> communication -> defense -> offenseelectrical field production electrical field production --Electric EelsElectric Eelsproduce up to 600 V (at 1 Amp)4/5 of body = electrogenesis organs3 organs: 1 communication, 2 more powerfuldischarge: disorient, stun or killalso: courtship, orientationEel Electric OrgansEel Electric OrgansElectric EelsElectric Eelselectrogenesis electrogenesis --Electric CatfishElectric CatfishAfrica, Nile; several genera in Fam. Melapteruridaeproduce up to 350 Vcourtship, huntingelectrogenesis electrogenesis --Electric RaysElectric Raysca. 70 species (Or. Torpediniformes)produce up to 8-220 Vpaired organs stun or killelectrogenesis electrogenesis --Weak Electric FishWeak Electric Fishca. 100 species knifefishtypically < 1 Vcommunication, object detectionelectrogenesis electrogenesis --Electric MammalElectric MammalAfrica’s Giant Otter-Shrew (Potamogale velox)aquatic; eats crabs, fishfishermen report shocksmagnetoreceptionmagnetoreceptionearth’s magnetic field linesmagnetoreceptionmagnetoreceptionHow? - mechanical vs. chemical vs. inductionpolarity vs. intensity & inclinationbiogenic magnetite (Fe3O4) = compass needleinclinationpolaritymagnetoreception magnetoreception --BirdsBirdsmigratory birds, homing pigeonsdisruption by magnetsmagnetosensory linked to vision:“see” Northlight-dependent sensormagnetite-based sensormagnetoreception magnetoreception --other animalsother animalssea turtleswhalessharkssalmonbeesmole ratssalamandersmagnetoreception magnetoreception --BacteriaBacteriaMagnetospirillum sp.magnetoreception magnetoreception --BacteriaBacteriamagnetoreception magnetoreception --BacteriaBacteriaexposure to electromagnetic (EM) fieldsexposure to electromagnetic (EM) fieldscancer rates - field correlationschildhood leukemia (CL) & electric utility workersCL doubled - fields > 0.4 μTCL increased 70% (< 200 m) transmission linesbrain cancer, Lou Gehrig’s, Alzheimer’s, miscarriageelectrical fields as cureselectrical fields as curesenhance bone depositionhip replacementbad breaksmany double-blind trialscell phone radiationcell phone radiationsome indications of cancer:Swedish study: 240% brain tumor increaseBritish study: no effectother studies: inconclusivebut ... improved reaction time & mental arithmeticMeisel - Biological Electrical Fields - p. 1 Biological Electric Fields Physics 208 Lecture Outline Dr. Joe E. Meisel Ceiba Foundation for Tropical Conservation I. Introduction A. overview of relevant fields a. electrical, magnetic, visible and thermal-IR spectrum d. detection (electroreception, magnetoreception) vs. production (electrogenesis) B. function within animals 1. nerve signals 2. muscle firing 3. action potential a. store charge differential, then release to generate current b. basis for some forms of electrogenesis 4. all living organisms produce some level of electric field a. cell membrane potential b. voltage-gated sodium, etc., channels C. animal sensory apparati 1. visible light: eyes, ocelli, etc a. Teresa: high-energy muon light detector 2.5 km down saw much bioluminescence 2. IR light: heat sensors in pit vipers, Haller’s organ in ticks o photons excite sensory cells, firing nervous signal 3. sound: waves in air or water (excellent propagation) o waves affect sensory hairs, triggering nervous signal 4. chemical: minute quantities in environment - tasted or smelled 5. gravity: recognize up from down 6. electromagnetic fields D. lecture overview 1. sensing EM fields 2. producing EM fields 3. physiological reaction to EM fields II. Electro-reception by animals A. how & why it works 1. all organisms (plants, animals, etc.) produce electric fields 2. detection of fields favored in environments without other stimuli 3. Deep-sea and tropical river environments a. DARK (deep, or turbid): no light detection -- chemical & other senses take over b. WET: excellent transmitter of sound, but also of electric currents 4. strong in predators and prey alike, but not grazers a. electrosensory organs likely modified for defensive, then offensive uses 5. also can detect abiotic objects, not just living organisms 6. commonly used for communication a. transmit/detect gender, size, identity, reproductive status, etc. b. species in same location avoid frequency overlap c. can shift frequency slightly to avoid “jamming” of conspecifics 7. passive vs. active electro-sensory
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