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Electric Eels Wield a Functional Venom Analogue. Toxins (Basel) 2021; 13:toxins13010048. [PMID: 33435184 PMCID: PMC7826911 DOI: 10.3390/toxins13010048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 12/30/2020] [Accepted: 01/07/2021] [Indexed: 12/23/2022] Open
Abstract
In this paper, I draw an analogy between the use of electricity by electric eels (Electrophorus electricus) to paralyze prey muscles and the use of venoms that paralyze prey by disrupting the neuromuscular junction. The eel’s strategy depends on the recently discovered ability of eels to activate prey motor neuron efferents with high-voltage pulses. Usually, eels use high voltage to cause brief, whole-body tetanus, thus preventing escape while swallowing prey whole. However, when eels struggle with large prey, or with prey held precariously, they often curl to bring their tail to the opposite side. This more than doubles the strength of the electric field within shocked prey, ensuring maximal stimulation of motor neuron efferents. Eels then deliver repeated volleys of high-voltage pulses at a rate of approximately 100 Hz. This causes muscle fatigue that attenuates prey movement, thus preventing both escape and defense while the eel manipulates and swallows the helpless animal. Presumably, the evolution of enough electrical power to remotely activate ion channels in prey efferents sets the stage for the selection of eel behaviors that functionally “poison” prey muscles.
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Song Z, Cao X, Horng TL, Huang H. Electric discharge of electrocytes: Modelling, analysis and simulation. J Theor Biol 2020; 498:110294. [PMID: 32348802 DOI: 10.1016/j.jtbi.2020.110294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 04/17/2020] [Accepted: 04/20/2020] [Indexed: 11/18/2022]
Abstract
In this paper, we investigate the electric discharge of electrocytes by extending our previous work on the generation of electric potential. We first give a complete formulation of a single cell unit consisting of an electrocyte and a resistor, based on a Poisson-Nernst-Planck (PNP) system with various membrane currents as interfacial conditions for the electrocyte and a Maxwell's model for the resistor. Our previous work can be treated as a special case with an infinite resistor (or open circuit). Using asymptotic analysis, we simplify our PNP system and reduce it to an ordinary differential equation (ODE) based model. Unlike the case of an infinite resistor, our numerical simulations of the new model reveal several distinct features. A finite current is generated, which leads to non-constant electric potentials in the bulk of intracellular and extracellular regions. Furthermore, the current induces an additional action potential (AP) at the non-innervated membrane, contrary to the case of an open circuit where an AP is generated only at the innervated membrane. The voltage drop inside the electrocyte is caused by an internal resistance due to mobile ions. We show that our single cell model can be used as the basis for a system with stacked electrocytes and the total current during the discharge of an electric eel can be estimated by using our model.
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Affiliation(s)
- Zilong Song
- Department of Mathematics, University of California, Riverside, CA 92521, U.S.A
| | - Xiulei Cao
- Department of Mathematics & Statistics, York University, Toronto, Ontario M3J 1P3, Canada
| | - Tzyy-Leng Horng
- Department of Applied Mathematics, Feng Chia University, Taichung 40724, Taiwan
| | - Huaxiong Huang
- BNU-UIC Joint Mathematical Research Centre, Zhuhai, Guangdong 519087, China; Department of Mathematics & Statistics, York University, Toronto, Ontario M3J 1P3, Canada; Department of Computer Science, University of Toronto, Toronto, Ontario M5T 3A1, Canada.
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Cao X, Song Z, Horng TL, Huang H. Electric potential generation of electrocytes: Modelling, analysis, and computation. J Theor Biol 2020; 487:110107. [PMID: 31836504 DOI: 10.1016/j.jtbi.2019.110107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Revised: 11/30/2019] [Accepted: 12/05/2019] [Indexed: 10/25/2022]
Abstract
In this paper, we developed a one-dimensional model for electric potential generation of electrocytes in electric eels. The model is based on the Poisson-Nernst-Planck system for ion transport coupled with membrane fluxes including the Hodgkin-Huxley type. Using asymptotic analysis, we derived a simplified zero-dimensional model, which we denote as the membrane model in this paper, as a leading order approximation. Our analysis provides justification for the assumption in membrane models that electric potential is constant in the intracellular space. This is essential to explain the superposition of two membrane potentials that leads to a significant transcellular potential. Numerical simulations are also carried out to support our analytical findings.
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Affiliation(s)
- Xiulei Cao
- Department of Mathematics and Statistics, York University, Toronto, Canada
| | - Zilong Song
- Department of Mathematics and Statistics, York University, Toronto, Canada
| | - Tzyy-Leng Horng
- Department of Applied Mathematics, Feng Chia University, Taichung 40724, Taiwan; National Center for Theoretical Sciences, Taipei Office, Taipei 10617, Taiwan
| | - Huaxiong Huang
- Department of Mathematics and Statistics, York University, Toronto, Canada; BNU-UIC Joint Mathematical Research Centre, Zhuhai, China; Department of Computer Science, University of Toronto, Toronto, Canada.
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O'Rourke DP, Baccanale CL, Stoskopf MK. Nontraditional Laboratory Animal Species (Cephalopods, Fish, Amphibians, Reptiles, and Birds). ILAR J 2019; 59:168-176. [PMID: 30462255 DOI: 10.1093/ilar/ily003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/18/2018] [Indexed: 12/27/2022] Open
Abstract
Aquatic vertebrates and cephalopods, amphibians, reptiles, and birds offer unique safety and occupational health challenges for laboratory animal personnel. This paper discusses environmental, handling, and zoonotic concerns associated with these species.
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Affiliation(s)
- Dorcas P O'Rourke
- Dorcas P. O'Rourke, DVM, MS, DACLAM, is Professor and Chair of the Department of Comparative Medicine at the Brody School of Medicine, East Carolina University in Greenville, North Carolina. Cecile L. Baccanale, DVM, is Associate Professor in the Department of Comparative Medicine at the Brody School of Medicine, East Carolina University in Greenville, North Carolina. Michael K. Stoskopf, DVM, PhD, DACZM, is Professor in the Department of Clinical Sciences, at the College of Veterinary Medicine as well as the Colleges of Natural Resources, Science, and Engineering at North Carolina State University in Raleigh, North Carolina
| | - Cecile L Baccanale
- Dorcas P. O'Rourke, DVM, MS, DACLAM, is Professor and Chair of the Department of Comparative Medicine at the Brody School of Medicine, East Carolina University in Greenville, North Carolina. Cecile L. Baccanale, DVM, is Associate Professor in the Department of Comparative Medicine at the Brody School of Medicine, East Carolina University in Greenville, North Carolina. Michael K. Stoskopf, DVM, PhD, DACZM, is Professor in the Department of Clinical Sciences, at the College of Veterinary Medicine as well as the Colleges of Natural Resources, Science, and Engineering at North Carolina State University in Raleigh, North Carolina
| | - Michael K Stoskopf
- Dorcas P. O'Rourke, DVM, MS, DACLAM, is Professor and Chair of the Department of Comparative Medicine at the Brody School of Medicine, East Carolina University in Greenville, North Carolina. Cecile L. Baccanale, DVM, is Associate Professor in the Department of Comparative Medicine at the Brody School of Medicine, East Carolina University in Greenville, North Carolina. Michael K. Stoskopf, DVM, PhD, DACZM, is Professor in the Department of Clinical Sciences, at the College of Veterinary Medicine as well as the Colleges of Natural Resources, Science, and Engineering at North Carolina State University in Raleigh, North Carolina
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Catania KC. The Astonishing Behavior of Electric Eels. Front Integr Neurosci 2019; 13:23. [PMID: 31379525 PMCID: PMC6646469 DOI: 10.3389/fnint.2019.00023] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Accepted: 06/24/2019] [Indexed: 11/29/2022] Open
Abstract
The remarkable physiology of the electric eel (Electrophorus electricus) made it one of the first model species in science. It was pivotal for understanding animal electricity in the 1700s, was investigated by Humboldt and Faraday in the 1800s, was leveraged to isolate the acetylcholine receptor in the 20th century, and has inspired the design of new power sources and provided insights to electric organ evolution in the 21st century. And yet few studies have investigated the electric eel’s behavior. This review focuses on a series of recently discovered behaviors that evolved alongside the eel’s extreme physiology. Eels use their high-voltage electric discharge to remotely control prey by transcutaneously activating motor neurons. Hunting eels use this behavior in two different ways. When prey have been detected, eels use high-voltage to cause immobility by inducing sustained, involuntary muscle contractions. On the other hand, when prey are hidden, eels often use brief pulses to induce prey twitch, which causes a water movement detected by the eel’s mechanoreceptors. Once grasped in the eel’s jaws, difficult prey are often subdued by sandwiching them between the two poles (head and tail) of the eel’s powerful electric organ. The resulting concentration of the high-voltage discharge, delivered at high-rates, causes involuntary fatigue in prey muscles. This novel strategy for inactivating muscles is functionally analogous to poisoning the neuromuscular junction with venom. For self-defense, electric eels leap from the water to directly electrify threats, efficiently activating nociceptors to deter their target. The latter behavior supports a legendary account by Alexander von Humboldt who described a battle between electric eels and horses in 1800. Finally, electric eels use high-voltage not only as a weapon, but also to efficiently track fast-moving prey with active electroreception. In conclusion, remarkable behaviors go hand in hand with remarkable physiology.
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Affiliation(s)
- Kenneth C Catania
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States
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