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Valiño G, Dunlap K, Quintana L. Androgen receptors rapidly modulate non-breeding aggression in male and female weakly electric fish (Gymnotus omarorum). Horm Behav 2024; 159:105475. [PMID: 38154435 DOI: 10.1016/j.yhbeh.2023.105475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 12/19/2023] [Accepted: 12/19/2023] [Indexed: 12/30/2023]
Abstract
The South American weakly electric fish, Gymnotus omarorum, displays territorial aggression year-round in both sexes. To examine the role of rapid androgen modulation in non-breeding aggression, we administered acetate cyproterone (CPA), a potent inhibitor of androgen receptors, to both male and females, just before staged agonistic interactions. Wild-caught fish were injected with CPA and, 30 min later, paired in intrasexual dyads. We then recorded the agonistic behavior which encompasses both locomotor displays and emission of social electric signals. We found that CPA had no discernible impact on the levels of aggression or the motivation to engage in aggressive behavior for either sex. However, CPA specifically decreased the expression of social electric signals in both males and female dyads. The effect was status-dependent as it only affected subordinate electrocommunication behavior, the emission of brief interruptions in their electric signaling ("offs"). This study is the first demonstration of a direct and rapid androgen effect mediated via androgen receptors on non-breeding aggression. Elucidating the mechanisms involved in non-breeding aggression in this teleost model allows us to better understand potentially conserved or convergent neuroendocrine mechanisms underlying aggression in vertebrates.
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Affiliation(s)
- Guillermo Valiño
- Departamento de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, MEC, Montevideo, Uruguay
| | - Kent Dunlap
- Department of Biology, Trinity College, Hartford, CT, United States
| | - Laura Quintana
- Departamento de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, MEC, Montevideo, Uruguay.
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Mucha S, Chapman LJ, Krahe R. The weakly electric fish, Apteronotus albifrons, actively avoids experimentally induced hypoxia. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2021; 207:369-379. [PMID: 33751182 PMCID: PMC8079295 DOI: 10.1007/s00359-021-01470-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 02/16/2021] [Accepted: 02/18/2021] [Indexed: 11/15/2022]
Abstract
Anthropogenic environmental degradation has led to an increase in the frequency and prevalence of aquatic hypoxia (low dissolved oxygen concentration, DO), which may affect habitat quality for water-breathing fishes. The weakly electric black ghost knifefish, Apteronotus albifrons, is typically found in well-oxygenated freshwater habitats in South America. Using a shuttle-box design, we exposed juvenile A. albifrons to a stepwise decline in DO from normoxia (> 95% air saturation) to extreme hypoxia (10% air saturation) in one compartment and chronic normoxia in the other. On average, A. albifrons actively avoided the hypoxic compartment below 22% air saturation. Hypoxia avoidance was correlated with upregulated swimming activity. Following avoidance, fish regularly ventured back briefly into deep hypoxia. Hypoxia did not affect the frequency of their electric organ discharges. Our results show that A. albifrons is able to sense hypoxia at non-lethal levels and uses active avoidance to mitigate its adverse effects.
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Affiliation(s)
- Stefan Mucha
- Institute of Biology, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany.
| | - Lauren J Chapman
- Department of Biology, McGill University, Montreal, QC, H3A 1B1, Canada
| | - Rüdiger Krahe
- Institute of Biology, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany.,Department of Biology, McGill University, Montreal, QC, H3A 1B1, Canada
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Pouso P, Radmilovich M, Silva A. An immunohistochemical study on the distribution of vasotocin neurons in the brain of two weakly electric fish, Gymnotus omarorum and Brachyhypopomus gauderio. Tissue Cell 2017; 49:257-269. [PMID: 28242105 DOI: 10.1016/j.tice.2017.02.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/21/2017] [Accepted: 02/05/2017] [Indexed: 10/20/2022]
Abstract
Hypothalamic nonapeptides (arginin vasotocin-vasopressin, oxytocin-isotocin) are known to modulate social behaviors across vertebrates. The neuroanatomical conservation of nonapeptide systems enables the use of novel vertebrate model species to identify general strategies of their functional mechanisms. We present a detailed immunohistochemical description of vasotocin (AVT) cell populations and their projections in two species of weakly electric fish with different social structure, Gymnotus omarorum and Brachyhypopomus gauderio. Strong behavioral, pharmacological, and electrophysiological evidence support that AVT modulation of electric behavior differs between the gregarious B. gauderio and the solitary G. omarorum. This functional diversity does not necessarily depend on anatomical differences of AVT neurons. To test this, we focus on interspecific comparisons of the AVT system in basal non-breeding males along the brain. G. omarorum and B. gauderio showed similar AVT somata sizes and comparable distributions of AVT somata and fibers. Interestingly, AVT fibers project to areas related to the control of social behavior and electromotor displays in both species. We found that no gross anatomical differences in the organization of the AVT system account for functional differences between species, which rather shall depend on the pattern of activation of neurons embedded in the same basic anatomical organization of the AVT system.
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Affiliation(s)
- Paula Pouso
- Depto Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay; Unidad Bases Neurales de la Conducta, Departamento de Neurofisiología Celular y Molecular, IIBCE, Montevideo 11600, Uruguay
| | - Milka Radmilovich
- Depto Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay
| | - Ana Silva
- Unidad Bases Neurales de la Conducta, Departamento de Neurofisiología Celular y Molecular, IIBCE, Montevideo 11600, Uruguay; Laboratorio de Neurociencias, Facultad de Ciencias, Universidad de la República, Montevideo 11400, Uruguay.
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Sullivan JP, Zuanon J, Cox Fernandes C. Two new species and a new subgenus of toothed Brachyhypopomus electric knifefishes ( Gymnotiformes, Hypopomidae) from the central Amazon and considerations pertaining to the evolution of a monophasic electric organ discharge. Zookeys 2013:1-34. [PMID: 24167419 PMCID: PMC3807744 DOI: 10.3897/zookeys.327.5427] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 08/09/2013] [Indexed: 11/23/2022] Open
Abstract
We describe two new, closely related species of toothed Brachyhypopomus (Hypopomidae: Gymnotiformes: Teleostei) from the central Amazon basin and create a new subgenus for them. Odontohypopomus, new subgenus of Brachyhypopomus, is diagnosed by (1) small teeth present on premaxillae; (2) medialmost two branchiostegal rays thin with blades oriented more vertically than remaining three rays; (3) background color in life (and to lesser extent in preservation) distinctly yellowish with head and sides peppered with small, widely spaced, very dark brown stellate chromatophores that greatly contrast with light background coloration; (4) a dark blotch or bar of subcutaneous pigment below the eye; (5) electric organ discharge waveform of very long duration (head-positive phase approx. 2 milliseconds or longer, head-negative phase shorter or absent) and slow pulse repetition rate (3–16 Hz). The type species of the new subgenus, Brachyhypopomus (Odontohypopomus) walteri sp. n., is diagnosed by the following additional character states: (1) subcutaneous dark pigment at base of orbit particularly prominent, (2) body semi-translucent and nearly bright yellow background coloration in life, (3) a biphasic electric organ discharge (EOD) waveform of very long duration (between 3.5 and 4 milliseconds at 25° C) with head-positive first phase significantly longer than second head-negative phase in both sexes. Brachyhypopomus (Odontohypopomus) bennetti sp. n. is diagnosed by two character states in addition to those used to diagnose the subgenus Odontohypopomus: (1) a deep electric organ, visible as large semi-transparent area, occupying approximately 14–17% body depth directly posterior to the abdominal cavity in combination with a short, but deep, caudal filament, and (2) a monophasic, head-positive EOD waveform, approximately 2.1 milliseconds in duration in both sexes. These are the only described rhamphichthyoid gymnotiforms with oral teeth, and Brachyhypopomus bennetti is the first Brachyhypopomus reported to have a monophasic (head-positive) EOD waveform. Unlike biphasic species, the waveform of its EOD is largely unaffected by tail damage from predators. Such injuries are common among specimens in our collections. This species’ preference for floating meadow habitat along the major channels of the Amazon River basin may put it at particularly high risk of predation and “tail grazing.”
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Affiliation(s)
- John P Sullivan
- Cornell University Museum of Vertebrates, 159 Sapsucker Woods Road, Ithaca, New York 14850 USA
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