1
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Wiser SD, Markham MR. Electrosensory and metabolic responses of weakly electric fish to changing water conductivity. J Exp Biol 2024; 227:jeb246269. [PMID: 38712896 DOI: 10.1242/jeb.246269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 04/24/2024] [Indexed: 05/08/2024]
Abstract
Weakly electric gymnotiform fishes use self-generated electric organ discharges (EODs) to navigate and communicate. The electrosensory range for these processes is a function of EOD amplitude, determined by the fish's electric organ (EO) output and the electrical conductivity of the surrounding water. Anthropogenic activity, such as deforestation, dams and industrial/agricultural runoff, are known to increase water conductivity in neotropical habitats, likely reducing the electrosensory range of these fish. We investigated whether fish modulate EO output as means of re-expanding electrosensory range after a rapid increase in water conductivity in the pulse-type Brachyhypopomus gauderio and the wave-type Eigenmannia virescens. Furthermore, because EOD production incurs significant metabolic costs, we assessed whether such compensation is associated with an increase in metabolic rate. Following the conductivity increase, B. gauderio increased EOD amplitude by 20.2±4.3% over 6 days but with no associated increase in metabolic rate, whereas the EOD amplitude of E. virescens remained constant, accompanied by an unexpected decrease in metabolic rate. Our results suggest that B. gauderio uses a compensation mechanism that requires no metabolic investment, such as impedance matching, or a physiological trade-off wherein energy is diverted from other physiological processes to increase EO output. These divergent responses between species could be the result of differences in reproductive life history or evolutionary adaptations to different aquatic habitats. Continued investigation of electrosensory responses to changing water conditions will be essential for understanding the effects of anthropogenic disturbances on gymnotiforms, and potential physiological mechanisms for adapting to a rapidly changing aquatic environment.
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Affiliation(s)
- Shannon D Wiser
- School of Biological Sciences, University of Oklahoma, Norman, OK 73019, USA
| | - Michael R Markham
- School of Biological Sciences, University of Oklahoma, Norman, OK 73019, USA
- Cellular & Behavioral Neurobiology Graduate Program, University of Oklahoma, Norman, OK 73019, USA
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2
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Caputi AA. Living life with an electric touch. J Exp Biol 2023; 226:jeb246060. [PMID: 38009325 DOI: 10.1242/jeb.246060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2023]
Abstract
The electric organ discharges (EODs) produced by weakly electric fish have long been a source of scientific intrigue and inspiration. The study of these species has contributed to our understanding of the organization of fixed action patterns, as well as enriching general imaging theory by unveiling the dual impact of an agent's actions on the environment and its own sensory system during the imaging process. This Centenary Review firstly compares how weakly electric fish generate species- and sex-specific stereotyped electric fields by considering: (1) peripheral mechanisms, including the geometry, channel repertoire and innervation of the electrogenic units; (2) the organization of the electric organs (EOs); and (3) neural coordination mechanisms. Secondly, the Review discusses the threefold function of the fish-centered electric fields: (1) to generate electric signals that encode the material, geometry and distance of nearby objects, serving as a short-range sensory modality or 'electric touch'; (2) to mark emitter identity and location; and (3) to convey social messages encoded in stereotypical modulations of the electric field that might be considered as species-specific communication symbols. Finally, this Review considers a range of potential research directions that are likely to be productive in the future.
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Affiliation(s)
- Angel Ariel Caputi
- Sistema Nacional de Investigadores - Uruguay, Av. Wilson Ferreira Aldunate 1219, Pando, PC 15600, Uruguay
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3
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Skeels S, von der Emde G, Burt de Perera T. Mormyrid fish as models for investigating sensory-motor integration: A behavioural perspective. J Zool (1987) 2023; 319:243-253. [PMID: 38515784 PMCID: PMC10953462 DOI: 10.1111/jzo.13046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 11/12/2022] [Accepted: 12/22/2022] [Indexed: 02/04/2023]
Abstract
Animals possess senses which gather information from their environment. They can tune into important aspects of this information and decide on the most appropriate response, requiring coordination of their sensory and motor systems. This interaction is bidirectional. Animals can actively shape their perception with self-driven motion, altering sensory flow to maximise the environmental information they are able to extract. Mormyrid fish are excellent candidates for studying sensory-motor interactions, because they possess a unique sensory system (the active electric sense) and exhibit notable behaviours that seem to be associated with electrosensing. This review will take a behavioural approach to unpicking this relationship, using active electrolocation as an example where body movements and sensing capabilities are highly related and can be assessed in tandem. Active electrolocation is the process where individuals will generate and detect low-voltage electric fields to locate and recognise nearby objects. We will focus on research in the mormyrid Gnathonemus petersii (G. petersii), given the extensive study of this species, particularly its object recognition abilities. By studying object detection and recognition, we can assess the potential benefits of self-driven movements to enhance selection of biologically relevant information. Finally, these findings are highly relevant to understanding the involvement of movement in shaping the sensory experience of animals that use other sensory modalities. Understanding the overlap between sensory and motor systems will give insight into how different species have become adapted to their environments.
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Affiliation(s)
- S. Skeels
- Department of BiologyUniversity of OxfordOxfordUK
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4
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Saenz DE, Gu T, Ban Y, Winemiller KO, Markham MR. Derived loss of signal complexity and plasticity in a genus of weakly electric fish. J Exp Biol 2021; 224:269075. [PMID: 34109419 PMCID: PMC8246343 DOI: 10.1242/jeb.242400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Accepted: 05/25/2021] [Indexed: 11/07/2022]
Abstract
Signal plasticity can maximize the usefulness of costly animal signals such as the electric organ discharges (EODs) of weakly electric fishes. Some species of the order Gymnotiformes rapidly alter their EOD amplitude and duration in response to circadian cues and social stimuli. How this plasticity is maintained across related species with different degrees of signal complexity is poorly understood. In one genus of weakly electric gymnotiform fish (Brachyhypopomus), only one species, B. bennetti, produces a monophasic signal while all other species emit complex biphasic or multiphasic EOD waveforms produced by two overlapping but asynchronous action potentials in each electric organ cell (electrocyte). One consequence of this signal complexity is the suppression of low-frequency signal content that is detectable by electroreceptive predators. In complex EODs, reduction of the EOD amplitude and duration during daytime inactivity can decrease both predation risk and the metabolic cost of EOD generation. We compared EOD plasticity and its underlying physiology in Brachyhypopomus focusing on B. bennetti. We found that B. bennetti exhibits minimal EOD plasticity, but that its electrocytes retained vestigial mechanisms of biphasic signaling and vestigial mechanisms for modulating the EOD amplitude. These results suggest that this species represents a transitional phenotypic state within a clade where signal complexity and plasticity were initially gained and then lost. Signal mimicry, mate recognition and sexual selection are potential factors maintaining the monophasic EOD phenotype in the face of detection by electroreceptive predators. Highlighted Article: In one electric fish genus, most species produce complex, plastic electric signals. One species that produces a simple signal shows reduced signal plasticity and retains vestigial mechanisms of signal complexity.
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Affiliation(s)
- David E Saenz
- Department of Ecology and Conservation Biology, Texas A&M University,College Station, TX 77843, USA
| | - Tingting Gu
- Sam Noble Microscopy Laboratory, University of Oklahoma, Norman, OK 73019, USA
| | - Yue Ban
- Neurobiology Section, Biological Sciences Division, University of California, San Diego, La Jolla, CA 92093, USA
| | - Kirk O Winemiller
- Department of Ecology and Conservation Biology, Texas A&M University,College Station, TX 77843, USA
| | - Michael R Markham
- Department of Biology, University of Oklahoma, Norman, OK 73019, USA.,Cellular & Behavioral Neurobiology Graduate Program, University of Oklahoma, Norman, OK 73019, USA
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5
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Fortune ES, Andanar N, Madhav M, Jayakumar RP, Cowan NJ, Bichuette ME, Soares D. Spooky Interaction at a Distance in Cave and Surface Dwelling Electric Fishes. Front Integr Neurosci 2020; 14:561524. [PMID: 33192352 PMCID: PMC7642693 DOI: 10.3389/fnint.2020.561524] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 09/07/2020] [Indexed: 11/30/2022] Open
Abstract
Glass knifefish (Eigenmannia) are a group of weakly electric fishes found throughout the Amazon basin. Their electric organ discharges (EODs) are energetically costly adaptations used in social communication and for localizing conspecifics and other objects including prey at night and in turbid water. Interestingly, a troglobitic population of blind cavefish Eigenmannia vicentespelea survives in complete darkness in a cave system in central Brazil. We examined the effects of troglobitic conditions, which includes a complete loss of visual cues and potentially reduced food sources, by comparing the behavior and movement of freely behaving cavefish to a nearby epigean (surface) population (Eigenmannia trilineata). We found that the strengths of electric discharges in cavefish were greater than in surface fish, which may result from increased reliance on electrosensory perception, larger size, and sufficient food resources. Surface fish were recorded while feeding at night and did not show evidence of territoriality, whereas cavefish appeared to maintain territories. Surprisingly, we routinely found both surface and cavefish with sustained differences in EOD frequencies that were below 10 Hz despite being within close proximity of about 50 cm. A half century of analysis of electrosocial interactions in laboratory tanks suggest that these small differences in EOD frequencies should have triggered the "jamming avoidance response," a behavior in which fish change their EOD frequencies to increase the difference between individuals. Pairs of fish also showed significant interactions between EOD frequencies and relative movements at large distances, over 1.5 m, and at high differences in frequencies, often >50 Hz. These interactions are likely "envelope" responses in which fish alter their EOD frequency in relation to higher order features, specifically changes in the depth of modulation, of electrosocial signals.
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Affiliation(s)
- Eric S. Fortune
- Biological Sciences, New Jersey Institute of Technology, Newark, NJ, United States
| | - Nicole Andanar
- Biological Sciences, New Jersey Institute of Technology, Newark, NJ, United States
| | - Manu Madhav
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, United States
| | | | - Noah J. Cowan
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, United States
| | - Maria Elina Bichuette
- Departamento de Ecologia e Biologia Evolutiva, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Daphne Soares
- Biological Sciences, New Jersey Institute of Technology, Newark, NJ, United States
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6
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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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7
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Waddell JC, Caputi AA. Waveform discrimination in a pair of pulse-generating electric fishes. JOURNAL OF FISH BIOLOGY 2020; 96:1065-1071. [PMID: 32077109 DOI: 10.1111/jfb.14298] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 01/07/2020] [Accepted: 01/17/2020] [Indexed: 06/10/2023]
Abstract
Studies of pulse-type gymnotiform electric fishes have suggested that electric organ discharge waveforms (EODw) allow individuals to discriminate between conspecific and allospecific signals, but few have approached this experimentally. Here we implement a phase-locked playback technique for a syntopic species pair, Brachyhypopomus gauderio and Gymnotus omarorum. Both species respond to changes in stimulus waveform with a transitory reduction in the interpulse interval of their self-generated discharge, providing strong evidence of discrimination. We also document sustained rate changes in response to different EODws, which may suggest recognition of natural waveforms.
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Affiliation(s)
- Joseph C Waddell
- Department of Integrative and Computational Neurosciences, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
| | - Angel A Caputi
- Department of Integrative and Computational Neurosciences, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
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8
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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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9
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Abstract
Neuroscience has a long, rich history in embracing unusual animals for research. Over the past several decades, there has been a technology-driven bottleneck in the species used for neuroscience research. However, an oncoming wave of technologies applicable to many animals hold promise for enabling researchers to address challenging scientific questions that cannot be solved using traditional laboratory animals. Here, we discuss how leveraging the convergent evolution of physiological or behavioral phenotypes can empower research mapping genotype to phenotype interactions. We present two case studies using electric fish and poison frogs and discuss how comparative work can teach us about evolutionary constraint and flexibility at various levels of biological organization. We also offer advice on the potential and pitfalls of establishing novel model systems in neuroscience research. Finally, we end with a discussion on the use of charismatic animals in neuroscience research and their utility in public outreach. Overall, we argue that convergent evolution frameworks can help identify generalizable principles of neuroscience.
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Affiliation(s)
- Jason R Gallant
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
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10
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Borde M, Quintana L, Comas V, Silva A. Hormone‐mediated modulation of the electromotor CPG in pulse‐type weakly electric fish. Commonalities and differences across species. Dev Neurobiol 2020; 80:70-80. [DOI: 10.1002/dneu.22732] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 11/21/2019] [Accepted: 01/08/2020] [Indexed: 12/28/2022]
Affiliation(s)
- Michel Borde
- Departamento de Fisiología Facultad de Medicina Universidad de la República Montevideo Uruguay
| | - Laura Quintana
- Unidad Bases Neurales de la Conducta Instituto de Investigaciones Biológicas Clemente Estable Montevideo Uruguay
| | - Virginia Comas
- Departamento de Fisiología Facultad de Medicina Universidad de la República Montevideo Uruguay
| | - Ana Silva
- Unidad Bases Neurales de la Conducta Instituto de Investigaciones Biológicas Clemente Estable Montevideo Uruguay
- Laboratorio de Neurociencias Facultad de Ciencias Universidad de la República Montevideo Uruguay
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11
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Crampton WGR. Electroreception, electrogenesis and electric signal evolution. JOURNAL OF FISH BIOLOGY 2019; 95:92-134. [PMID: 30729523 DOI: 10.1111/jfb.13922] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 02/05/2019] [Indexed: 05/06/2023]
Abstract
Electroreception, the capacity to detect external underwater electric fields with specialised receptors, is a phylogenetically widespread sensory modality in fishes and amphibians. In passive electroreception, a capacity possessed by c. 16% of fish species, an animal uses low-frequency-tuned ampullary electroreceptors to detect microvolt-range bioelectric fields from prey, without the need to generate its own electric field. In active electroreception (electrolocation), which occurs only in the teleost lineages Mormyroidea and Gymnotiformes, an animal senses its surroundings by generating a weak (< 1 V) electric-organ discharge (EOD) and detecting distortions in the EOD-associated field using high-frequency-tuned tuberous electroreceptors. Tuberous electroreceptors also detect the EODs of neighbouring fishes, facilitating electrocommunication. Several other groups of elasmobranchs and teleosts generate weak (< 10 V) or strong (> 50 V) EODs that facilitate communication or predation, but not electrolocation. Approximately 1.5% of fish species possess electric organs. This review has two aims. First, to synthesise our knowledge of the functional biology and phylogenetic distribution of electroreception and electrogenesis in fishes, with a focus on freshwater taxa and with emphasis on the proximate (morphological, physiological and genetic) bases of EOD and electroreceptor diversity. Second, to describe the diversity, biogeography, ecology and electric signal diversity of the mormyroids and gymnotiforms and to explore the ultimate (evolutionary) bases of signal and receptor diversity in their convergent electrogenic-electrosensory systems. Four sets of potential drivers or moderators of signal diversity are discussed. First, selective forces of an abiotic (environmental) nature for optimal electrolocation and communication performance of the EOD. Second, selective forces of a biotic nature targeting the communication function of the EOD, including sexual selection, reproductive interference from syntopic heterospecifics and selection from eavesdropping predators. Third, non-adaptive drift and, finally, phylogenetic inertia, which may arise from stabilising selection for optimal signal-receptor matching.
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12
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Baker CVH, Modrell MS. Insights into Electroreceptor Development and Evolution from Molecular Comparisons with Hair Cells. Integr Comp Biol 2019; 58:329-340. [PMID: 29846597 DOI: 10.1093/icb/icy037] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The vertebrate lateral line system comprises a mechanosensory division, with neuromasts containing hair cells that detect local water movement ("distant touch"); and an electrosensory division, with electrosensory organs that detect the weak, low-frequency electric fields surrounding other animals in water (primarily used for hunting). The entire lateral line system was lost in the amniote lineage with the transition to fully terrestrial life; the electrosensory division was lost independently in several lineages, including the ancestors of frogs and of teleost fishes. (Electroreception with different characteristics subsequently evolved independently within two teleost lineages.) Recent gene expression studies in a non-teleost actinopterygian fish suggest that electroreceptor ribbon synapses employ the same transmission mechanisms as hair cell ribbon synapses, and show that developing electrosensory organs express transcription factors essential for hair cell development, including Atoh1 and Pou4f3. Previous hypotheses for electroreceptor evolution suggest either that electroreceptors and hair cells evolved independently in the vertebrate ancestor from a common ciliated secondary cell, or that electroreceptors evolved from hair cells. The close developmental and putative physiological similarities implied by the gene expression data support the latter hypothesis, i.e., that electroreceptors evolved in the vertebrate ancestor as a "sister cell-type" to lateral line hair cells.
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Affiliation(s)
- Clare V H Baker
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, UK
| | - Melinda S Modrell
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, UK
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Silva AC. Hormonal Influences on Social Behavior in South American Weakly Electric Fishes. ELECTRORECEPTION: FUNDAMENTAL INSIGHTS FROM COMPARATIVE APPROACHES 2019. [DOI: 10.1007/978-3-030-29105-1_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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14
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Joos B, Markham MR, Lewis JE, Morris CE. A model for studying the energetics of sustained high frequency firing. PLoS One 2018; 13:e0196508. [PMID: 29708986 PMCID: PMC5927439 DOI: 10.1371/journal.pone.0196508] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 04/13/2018] [Indexed: 11/25/2022] Open
Abstract
Regulating membrane potential and synaptic function contributes significantly to the energetic costs of brain signaling, but the relative costs of action potentials (APs) and synaptic transmission during high-frequency firing are unknown. The continuous high-frequency (200-600Hz) electric organ discharge (EOD) of Eigenmannia, a weakly electric fish, underlies its electrosensing and communication. EODs reflect APs fired by the muscle-derived electrocytes of the electric organ (EO). Cholinergic synapses at the excitable posterior membranes of the elongated electrocytes control AP frequency. Based on whole-fish O2 consumption, ATP demand per EOD-linked AP increases exponentially with AP frequency. Continual EOD-AP generation implies first, that ion homeostatic processes reliably counteract any dissipation of posterior membrane ENa and EK and second that high frequency synaptic activation is reliably supported. Both of these processes require energy. To facilitate an exploration of the expected energy demands of each, we modify a previous excitability model and include synaptic currents able to drive APs at frequencies as high as 600 Hz. Synaptic stimuli are modeled as pulsatile cation conductance changes, with or without a small (sustained) background conductance. Over the full species range of EOD frequencies (200–600 Hz) we calculate frequency-dependent “Na+-entry budgets” for an electrocyte AP as a surrogate for required 3Na+/2K+-ATPase activity. We find that the cost per AP of maintaining constant-amplitude APs increases nonlinearly with frequency, whereas the cost per AP for synaptic input current is essentially constant. This predicts that Na+ channel density should correlate positively with EOD frequency, whereas AChR density should be the same across fish. Importantly, calculated costs (inferred from Na+-entry through Nav and ACh channels) for electrocyte APs as frequencies rise are much less than expected from published whole-fish EOD-linked O2 consumption. For APs at increasingly high frequencies, we suggest that EOD-related costs external to electrocytes (including packaging of synaptic transmitter) substantially exceed the direct cost of electrocyte ion homeostasis.
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Affiliation(s)
- Bela Joos
- Department of Physics, University of Ottawa, Ottawa, Ontario, Canada
- Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, Canada
- * E-mail:
| | - Michael R. Markham
- Department of Biology, The University of Oklahoma, Norman, Oklahoma, United States of America
| | - John E. Lewis
- Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, Canada
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Catherine E. Morris
- Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario, Canada
- Neuroscience, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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15
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Traeger LL, Sabat G, Barrett-Wilt GA, Wells GB, Sussman MR. A tail of two voltages: Proteomic comparison of the three electric organs of the electric eel. SCIENCE ADVANCES 2017; 3:e1700523. [PMID: 28695212 PMCID: PMC5498108 DOI: 10.1126/sciadv.1700523] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 05/19/2017] [Indexed: 05/22/2023]
Abstract
The electric eel (Electrophorus electricus) is unusual among electric fishes because it has three pairs of electric organs that serve multiple biological functions: For navigation and communication, it emits continuous pulses of weak electric discharge (<1 V), but for predation and defense, it intermittently emits lethal strong electric discharges (10 to 600 V). We hypothesized that these two electrogenic outputs have different energetic demands reflected by differences in their proteome and phosphoproteome. We report the use of isotope-assisted quantitative mass spectrometry to test this hypothesis. We observed novel phosphorylation sites in sodium transporters and identified a potassium channel with unique differences in protein concentration among the electric organs. In addition, we found transcription factors and protein kinases that show differential abundance in the strong versus weak electric organs. Our findings support the hypothesis that proteomic differences among electric organs underlie differences in energetic needs, reflecting a trade-off between generating weak voltages continuously and strong voltages intermittently.
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Affiliation(s)
- Lindsay L. Traeger
- Department of Genetics, University of Wisconsin-Madison, Madison, WI 53706, USA
- Biotechnology Center, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Grzegorz Sabat
- Biotechnology Center, University of Wisconsin-Madison, Madison, WI 53706, USA
| | | | - Gregg B. Wells
- Department of Molecular and Cellular Medicine, Texas A&M University, College Station, TX 77843, USA
| | - Michael R. Sussman
- Biotechnology Center, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
- Corresponding author.
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16
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Abstract
When approached by a large, partially submerged conductor, electric eels (Electrophorus electricus) will often defend themselves by leaping from the water to directly shock the threat. Presumably, the conductor is interpreted as an approaching terrestrial or semiaquatic animal. In the course of this defensive behavior, eels first make direct contact with their lower jaw and then rapidly emerge from the water, ascending the conductor while discharging high-voltage volleys. In this study, the equivalent circuit that develops during this behavior was proposed and investigated. First, the electromotive force and internal resistance of four electric eels were determined. These values were then used to estimate the resistance of the water volume between the eel and the conductor by making direct measurements of current with the eel and water in the circuit. The resistance of the return path from the eel's lower jaw to the main body of water was then determined, based on voltage recordings, for each electric eel at the height of the defensive leap. Finally, the addition of a hypothetical target for the leaping defense was considered as part of the circuit. The results suggest the defensive behavior efficiently directs electrical current through the threat, producing an aversive and deterring experience by activating afferents in potential predators.
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Affiliation(s)
- Kenneth C Catania
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
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17
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Waddell JC, Rodríguez-Cattáneo A, Caputi AA, Crampton WGR. Electric organ discharges and near-field spatiotemporal patterns of the electromotive force in a sympatric assemblage of Neotropical electric knifefish. ACTA ACUST UNITED AC 2016; 110:164-181. [PMID: 27794446 DOI: 10.1016/j.jphysparis.2016.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 09/11/2016] [Accepted: 10/25/2016] [Indexed: 10/20/2022]
Abstract
Descriptions of the head-to-tail electric organ discharge (ht-EOD) waveform - typically recorded with electrodes at a distance of approximately 1-2 body lengths from the center of the subject - have traditionally been used to characterize species diversity in gymnotiform electric fish. However, even taxa with relatively simple ht-EODs show spatiotemporally complex fields near the body surface that are determined by site-specific electrogenic properties of the electric organ and electric filtering properties of adjacent tissues and skin. In Brachyhypopomus, a pulse-discharging genus in the family Hypopomidae, the regional characteristics of the electric organ and the role that the complex 'near field' plays in communication and/or electrolocation are not well known. Here we describe, compare, and discuss the functional significance of diversity in the ht-EOD waveforms and near-field spatiotemporal patterns of the electromotive force (emf-EODs) among a species-rich sympatric community of Brachyhypopomus from the upper Amazon.
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Affiliation(s)
- Joseph C Waddell
- Department of Biology, University of Central Florida, Orlando, FL, United States
| | - Alejo Rodríguez-Cattáneo
- Department of Integrative and Computational Neurosciences, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
| | - Angel A Caputi
- Department of Integrative and Computational Neurosciences, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay.
| | - William G R Crampton
- Department of Biology, University of Central Florida, Orlando, FL, United States.
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18
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Pitchers WR, Constantinou SJ, Losilla M, Gallant JR. Electric fish genomics: Progress, prospects, and new tools for neuroethology. ACTA ACUST UNITED AC 2016; 110:259-272. [PMID: 27769923 DOI: 10.1016/j.jphysparis.2016.10.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 09/06/2016] [Accepted: 10/16/2016] [Indexed: 01/01/2023]
Abstract
Electric fish have served as a model system in biology since the 18th century, providing deep insight into the nature of bioelectrogenesis, the molecular structure of the synapse, and brain circuitry underlying complex behavior. Neuroethologists have collected extensive phenotypic data that span biological levels of analysis from molecules to ecosystems. This phenotypic data, together with genomic resources obtained over the past decades, have motivated new and exciting hypotheses that position the weakly electric fish model to address fundamental 21st century biological questions. This review article considers the molecular data collected for weakly electric fish over the past three decades, and the insights that data of this nature has motivated. For readers relatively new to molecular genetics techniques, we also provide a table of terminology aimed at clarifying the numerous acronyms and techniques that accompany this field. Next, we pose a research agenda for expanding genomic resources for electric fish research over the next 10years. We conclude by considering some of the exciting research prospects for neuroethology that electric fish genomics may offer over the coming decades, if the electric fish community is successful in these endeavors.
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Affiliation(s)
- William R Pitchers
- Dept. of Integrative Biology, Michigan State University, 288 Farm Lane RM 203, East Lansing, MI 48824, USA.
| | - Savvas J Constantinou
- Dept. of Integrative Biology, Michigan State University, 288 Farm Lane RM 203, East Lansing, MI 48824, USA
| | - Mauricio Losilla
- Dept. of Integrative Biology, Michigan State University, 288 Farm Lane RM 203, East Lansing, MI 48824, USA
| | - Jason R Gallant
- Dept. of Integrative Biology, Michigan State University, 288 Farm Lane RM 203, East Lansing, MI 48824, USA.
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19
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Phylogenetic Systematics, Biogeography, and Ecology of the Electric Fish Genus Brachyhypopomus (Ostariophysi: Gymnotiformes). PLoS One 2016; 11:e0161680. [PMID: 27736882 PMCID: PMC5063478 DOI: 10.1371/journal.pone.0161680] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 08/10/2016] [Indexed: 11/23/2022] Open
Abstract
A species-level phylogenetic reconstruction of the Neotropical bluntnose knifefish genus Brachyhypopomus (Gymnotiformes, Hypopomidae) is presented, based on 60 morphological characters, approximately 1100 base pairs of the mitochondrial cytb gene, and approximately 1000 base pairs of the nuclear rag2 gene. The phylogeny includes 28 species of Brachyhypopomus and nine outgroup species from nine other gymnotiform genera, including seven in the superfamily Rhamphichthyoidea (Hypopomidae and Rhamphichthyidae). Parsimony and Bayesian total evidence phylogenetic analyses confirm the monophyly of the genus, and identify nine robust species groups. Homoplastic osteological characters associated with diminutive body size and occurrence in small stream habitats, including loss of squamation and simplifications of the skeleton, appear to mislead a phylogenetic analysis based on morphological characters alone–resulting in the incorrect placing of Microsternarchus + Racenisia in a position deeply nested within Brachyhypopomus. Consideration of geographical distribution in light of the total evidence phylogeny indicates an origin for Brachyhypopomus in Greater Amazonia (the superbasin comprising the Amazon, Orinoco and major Guiana drainages), with subsequent dispersal and vicariance in peripheral basins, including the La Plata, the São Francisco, and trans-Andean basins of northwest South America and Central America. The ancestral habitat of Brachyhypopomus likely resembled the normoxic, low-conductivity terra firme stream system occupied by many extant species, and the genus has subsequently occupied a wide range of terra firme and floodplain habitats including low- and high-conductivity systems, and normoxic and hypoxic systems. Adaptations for impedance matching to high conductivity, and/or for air breathing in hypoxic systems have attended these habitat transitions. Several species of Brachyhypopomus are eurytopic with respect to habitat occupancy and these generally exhibit wider geographical ranges than stenotopic species.
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20
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Markham MR, Ban Y, McCauley AG, Maltby R. Energetics of Sensing and Communication in Electric Fish: A Blessing and a Curse in the Anthropocene? Integr Comp Biol 2016; 56:889-900. [PMID: 27549201 DOI: 10.1093/icb/icw104] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Weakly electric freshwater fish use self-generated electric fields to image their worlds and communicate in the darkness of night and turbid waters. This active sensory/communication modality evolved independently in the freshwaters of South America and Africa, where hundreds of electric fish species are broadly and abundantly distributed. The adaptive advantages of the sensory capacity to forage and communicate in visually-unfavorable environments and outside the detection of visually-guided predators likely contributed to the broad success of these clades across a variety of Afrotropical and neotropical habitats. Here we consider the potentially high and limiting metabolic costs of the active sensory and communication signals that define the gymnotiform weakly electric fish of South America. Recent evidence from two well-studied species suggests that the metabolic costs of electrogenesis can be quite high, sometimes exceeding one-fourth of these fishes' daily energy budget. Supporting such an energetically expensive system has shaped a number of cellular, endocrine, and behavioral adaptations to restrain the metabolic costs of electrogenesis in general or in response to metabolic stress. Despite a suite of adaptations supporting electrogenesis, these weakly electric fish are vulnerable to metabolic stresses such as hypoxia and food restriction. In these conditions, fish reduce signal amplitude presumably as a function of absolute energy shortfall or as a proactive means to conserve energy. In either case, reducing signal amplitude compromises both sensory and communication performance. Such outcomes suggest that the higher metabolic cost of active sensing and communication in weakly electric fish compared with the sensory and communication systems in other neotropical fish might mean that weakly electric fish are disproportionately susceptible to harm from anthropogenic disturbances of neotropical aquatic habitats. Fully evaluating this possibility, however, will require broad comparative studies of metabolic energetics across the diverse clades of gymnotiform electric fish and in comparison to other nonelectric neotropical fishes.
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Affiliation(s)
- Michael R Markham
- *Department of Biology, The University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA .,†Cellular & Behavioral Neurobiology Graduate Program, The University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA
| | - Yue Ban
- *Department of Biology, The University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA.,†Cellular & Behavioral Neurobiology Graduate Program, The University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA
| | - Austin G McCauley
- *Department of Biology, The University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA
| | - Rosalie Maltby
- *Department of Biology, The University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA
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21
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Crampton WGR, Santana CDD, Waddell JC, Lovejoy NR. A taxonomic revision of the Neotropical electric fish genus Brachyhypopomus (Ostariophysi: Gymnotiformes: Hypopomidae), with descriptions of 15 new species. NEOTROPICAL ICHTHYOLOGY 2016. [DOI: 10.1590/1982-0224-20150146] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ABSTRACT The bluntnose knifefish genus BrachyhypopomusMago-Leccia, 1994, is diagnosed from other Rhamphichthyoidea (Rhamphichthyidae + Hypopomidae) by the presence of a disk-like ossification in the anterior portion of the palatoquadrate, and by the following external characters: short snout, 18.7-32.6% of head length (vs. 33.3-68.6% in Hypopomus, Gymnorhamphichthys, Iracema, and Rhamphichthys), absence of a paired accessory electric organ in the mental or humeral region (vs. presence in Hypopygus and Steatogenys), presence of 3-4 pectoral proximal radials (vs. 5 in Akawaio), presence of the antorbital + infraorbital, and the preopercular cephalic lateral line canal bones (vs. absence in Racenisia). Brachyhypopomus cannot be diagnosed unambiguously from Microsternarchus or from Procerusternarchus on the basis of external characters alone. Brachyhypopomus comprises 28 species. Here we describe 15 new species, and provide redescriptions of all 13 previously described species, based on meristic, morphometric, and other morphological characters. We include notes on ecology and natural history for each species, and provide regional dichotomous keys and distribution maps, based on the examination of 12,279 specimens from 2,787 museum lots. A lectotype is designated for Brachyhypopomus pinnicaudatus (Hopkins, Comfort, Bastian & Bass, 1990). Brachyhypopomus species are abundant in shallow lentic and slow-flowing freshwater habitats from southern Costa Rica and northern Venezuela to Uruguay and northern Argentina. Species diversity is highest in Greater Amazonia, where 20 species occur: B. alberti, new species, B. arrayae, new species, and B. cunia, new species, in the upper rio Madeira drainage; B. batesi, new species, in the central Amazon and rio Negro; B. beebei, B. brevirostris, B. regani, new species, B. sullivani, new species, and B. walteri, widespread through the Amazon and Orinoco basins and the Guianas; B. belindae, new species, in the central Amazon basin; B. benjamini, new species, and B. verdii, new species, in the upper Amazon basin; B. bennetti, in the upper, central, and lower Amazon, lower Tocantins, and upper Madeira basins; B. bullocki in the Orinoco, Negro and Essequibo drainages; B. diazi in the Orinoco Llanos; B. flavipomus, new species, and B. hamiltoni, new species, in the central and upper Amazon basin; B. hendersoni, new species, in the central Amazon, lower Negro and Essequibo basins; B. pinnicaudatus in the central and lower Amazon, lower, upper Madeira, lower Tocantins and Mearim basins, and coastal French Guiana; and B. provenzanoi, new species, in the upper Orinoco and upper Negro basins. Five species are known from the Paraná-Paraguay-Uruguay basin and adjacent southern Atlantic drainages: B. bombilla in the lower Paraná, upper, central, and lower Paraguay, Uruguay and Patos-Mirim drainages; B. brevirostris in the upper Paraguay basin; B. draco in the lower Paraná, lower Paraguay, Uruguay, Patos-Mirim, and Tramandaí basins; B. gauderio in the lower Paraná, upper, central, and lower Paraguay, Uruguay, Patos-Mirim and Tramandaí basins; and B. walteri in the lower Paraná and upper Paraguay basins. Two species occur in small Atlantic drainages of southern Brazil: B. janeiroensis in the São João, Paraíba and small intervening drainages; and B. jureiae in the Ribeira de Iguape and Una do Prelado. One species occurs in the middle and upper São Francisco basin: B. menezesi, new species. Three species occur in trans-Andean drainages: B. diazi in Caribbean drainages of northern Venezuela; B. occidentalis in Atlantic and Pacific drainages of southern Costa Rica and Panama to Darién, and the Maracaibo, Magdalena, Sinú and Atrato drainages; and B. palenque, new species, in Pacific drainages of Ecuador.
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22
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Abstract
The high voltage discharge generated by electric eels is a powerful predatory weapon. A new study shows that eels exploit basic physics to increase the voltage delivered to prey, inducing muscle fatigue that turns challenging prey items into easy targets.
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Affiliation(s)
- Bruce A Carlson
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA.
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23
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Shifman AR, Longtin A, Lewis JE. Ultrafast traveling wave dominates the electric organ discharge of Apteronotus leptorhynchus: an inverse modelling study. Sci Rep 2015; 5:15780. [PMID: 26514932 PMCID: PMC4626797 DOI: 10.1038/srep15780] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 10/05/2015] [Indexed: 11/30/2022] Open
Abstract
Identifying and understanding the current sources that give rise to bioelectric fields is a fundamental problem in the biological sciences. It is very difficult, for example, to attribute the time-varying features of an electroencephalogram recorded from the head surface to the neural activity of specific brain areas; model systems can provide important insight into such problems. Some species of fish actively generate an oscillating (c. 1000 Hz) quasi-dipole electric field to communicate and sense their environment in the dark. A specialized electric organ comprises neuron-like cells whose collective signal underlies this electric field. As a step towards understanding the detailed biophysics of signal generation in these fish, we use an anatomically-detailed finite-element modelling approach to reverse-engineer the electric organ signal over one oscillation cycle. We find that the spatiotemporal profile of current along the electric organ constitutes a travelling wave that is well-described by two spatial Fourier components varying in time. The conduction velocity of this wave is faster than action potential conduction in any known neuronal axon (>200 m/s), suggesting that the spatiotemporal features of high-frequency electric organ discharges are not constrained by the conduction velocities of spinal neuron pathways.
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Affiliation(s)
- Aaron R Shifman
- Department of Biology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.,Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - André Longtin
- Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.,Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - John E Lewis
- Department of Biology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.,Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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24
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Traeger LL, Volkening JD, Moffett H, Gallant JR, Chen PH, Novina CD, Phillips GN, Anand R, Wells GB, Pinch M, Güth R, Unguez GA, Albert JS, Zakon H, Sussman MR, Samanta MP. Unique patterns of transcript and miRNA expression in the South American strong voltage electric eel (Electrophorus electricus). BMC Genomics 2015; 16:243. [PMID: 25887781 PMCID: PMC4393597 DOI: 10.1186/s12864-015-1288-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 01/26/2015] [Indexed: 11/10/2022] Open
Abstract
Background With its unique ability to produce high-voltage electric discharges in excess of 600 volts, the South American strong voltage electric eel (Electrophorus electricus) has played an important role in the history of science. Remarkably little is understood about the molecular nature of its electric organs. Results We present an in-depth analysis of the genome of E. electricus, including the transcriptomes of eight mature tissues: brain, spinal cord, kidney, heart, skeletal muscle, Sachs’ electric organ, main electric organ, and Hunter’s electric organ. A gene set enrichment analysis based on gene ontology reveals enriched functions in all three electric organs related to transmembrane transport, androgen binding, and signaling. This study also represents the first analysis of miRNA in electric fish. It identified a number of miRNAs displaying electric organ-specific expression patterns, including one novel miRNA highly over-expressed in all three electric organs of E. electricus. All three electric organ tissues also express three conserved miRNAs that have been reported to inhibit muscle development in mammals, suggesting that miRNA-dependent regulation of gene expression might play an important role in specifying an electric organ identity from its muscle precursor. These miRNA data were supported using another complete miRNA profile from muscle and electric organ tissues of a second gymnotiform species. Conclusions Our work on the E. electricus genome and eight tissue-specific gene expression profiles will greatly facilitate future research on determining the coding and regulatory sequences that specify the function, development, and evolution of electric organs. Moreover, these data and future studies will be informed by the first comprehensive analysis of miRNA expression in an electric fish presented here. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1288-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lindsay L Traeger
- Department of Genetics, University of Wisconsin, Madison, WI, 53706, USA. .,Biotechnology Center, University of Wisconsin, Madison, WI, 53706, USA.
| | - Jeremy D Volkening
- Biotechnology Center, University of Wisconsin, Madison, WI, 53706, USA. .,Department of Biochemistry, University of Wisconsin, Madison, WI, 53706, USA.
| | - Howell Moffett
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA, 02115, USA. .,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Jason R Gallant
- Department of Zoology, Michigan State University, East Lansing, MI, 48824, USA. .,BEACON Center for the Study of Evolution in Action, Lansing, USA.
| | - Po-Hao Chen
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA, 02115, USA. .,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA. .,Broad Institute of Harvard and MIT, Cambridge, MA, 02141, USA.
| | - Carl D Novina
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA, 02115, USA. .,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA. .,Broad Institute of Harvard and MIT, Cambridge, MA, 02141, USA.
| | - George N Phillips
- BioSciences at Rice and Department of Chemistry, Rice University, Houston, TX, 77005, USA.
| | - Rene Anand
- Department of Pharmacology and Department of Neuroscience, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
| | - Gregg B Wells
- Department of Molecular and Cellular Medicine, Texas A&M University, College Station, TX, 77483, USA.
| | - Matthew Pinch
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA.
| | - Robert Güth
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA.
| | - Graciela A Unguez
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA.
| | - James S Albert
- Department of Biology, University of Louisiana, Lafayette, LA, 70503, USA.
| | - Harold Zakon
- BEACON Center for the Study of Evolution in Action, Lansing, USA. .,University of Texas, Austin, TX, 78712, USA. .,The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, The Marine Biological Laboratory, Woods Hole, MA, 02543, USA.
| | - Michael R Sussman
- Biotechnology Center, University of Wisconsin, Madison, WI, 53706, USA. .,Department of Biochemistry, University of Wisconsin, Madison, WI, 53706, USA.
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25
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Abstract
Electric fish image their environments and communicate by generating electric organ discharges through the simultaneous action potentials (APs) of electric organ cells (electrocytes) in the periphery. Steatogenys elegans generates a biphasic electrocyte discharge by the precisely regulated timing and waveform of APs generated from two excitable membranes present in each electrocyte. Current-clamp recordings of electrocyte APs reveal that the posterior membrane fires first, followed ∼30 μs later by an AP on the anterior membrane. This delay was maintained even as the onset of the first AP was advanced >5 ms by increasing stimulus intensity and across multiple spikes during bursts of APs elicited by prolonged stimulation. Simultaneous cell-attached loose-patch recordings of Na(+) currents on each membrane revealed that activation voltage for Na(+) channels on the posterior membrane was 10 mV hyperpolarized compared with Na(+) channels on the anterior membrane, with no differences in activation or inactivation kinetics. Computational simulations of electrocyte APs demonstrated that this difference in Na(+) current activation voltage was sufficient to maintain the proper firing order and the interspike delay. A similar difference in activation threshold has been reported for the Na(+) currents of the axon initial segment compared with somatic Na(+) channels of pyramidal neurons, suggesting convergent evolution of spike initiation and timing mechanisms across different systems of excitable cells.
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26
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Salazar VL, Krahe R, Lewis JE. The energetics of electric organ discharge generation in gymnotiform weakly electric fish. ACTA ACUST UNITED AC 2014; 216:2459-68. [PMID: 23761471 DOI: 10.1242/jeb.082735] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Gymnotiform weakly electric fish produce an electric signal to sense their environment and communicate with conspecifics. Although the generation of such relatively large electric signals over an entire lifetime is expected to be energetically costly, supporting evidence to date is equivocal. In this article, we first provide a theoretical analysis of the energy budget underlying signal production. Our analysis suggests that wave-type and pulse-type species invest a similar fraction of metabolic resources into electric signal generation, supporting previous evidence of a trade-off between signal amplitude and frequency. We then consider a comparative and evolutionary framework in which to interpret and guide future studies. We suggest that species differences in signal generation and plasticity, when considered in an energetics context, will not only help to evaluate the role of energetic constraints in the evolution of signal diversity but also lead to important general insights into the energetics of bioelectric signal generation.
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Affiliation(s)
- Vielka L Salazar
- Department of Biology, Cape Breton University, Sydney, NS, Canada, B1P 6L2
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27
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Krahe R, Fortune ES. Electric fishes: neural systems, behaviour and evolution. ACTA ACUST UNITED AC 2014; 216:2363-4. [PMID: 23761461 DOI: 10.1242/jeb.091322] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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