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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] [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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Smith GT, Proffitt MR, Smith AR, Rusch DB. Genes linked to species diversity in a sexually dimorphic communication signal in electric fish. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2017; 204:93-112. [PMID: 29058069 DOI: 10.1007/s00359-017-1223-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 09/17/2017] [Accepted: 09/25/2017] [Indexed: 02/06/2023]
Abstract
Sexually dimorphic behaviors are often regulated by androgens and estrogens. Steroid receptors and metabolism are control points for evolutionary changes in sexual dimorphism. Electric communication signals of South American knifefishes are a model for understanding the evolution and physiology of sexually dimorphic behavior. These signals are regulated by gonadal steroids and controlled by a simple neural circuit. Sexual dimorphism of the signals varies across species. We used transcriptomics to examine mechanisms for sex differences in electric organ discharges (EODs) of two closely related species, Apteronotus leptorhynchus and Apteronotus albifrons, with reversed sexual dimorphism in their EODs. The pacemaker nucleus (Pn), which controls EOD frequency (EODf), expressed transcripts for steroid receptors and metabolizing enzymes, including androgen receptors, estrogen receptors, aromatase, and 5α-reductase. The Pn expressed mRNA for ion channels likely to regulate the high-frequency activity of Pn neurons and for neuromodulator and neurotransmitter receptors that may regulate EOD modulations used in aggression and courtship. Expression of several ion channel genes, including those for Kir3.1 inward-rectifying potassium channels and sodium channel β1 subunits, was sex-biased or correlated with EODf in ways consistent with EODf sex differences. Our findings provide a basis for future studies to characterize neurogenomic mechanisms by which sex differences evolve.
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Affiliation(s)
- G Troy Smith
- Department of Biology, Indiana University, Jordan Hall, 1001 E. 3rd St., Bloomington, IN, 47405, USA. .,Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA.
| | - Melissa R Proffitt
- Department of Biology, Indiana University, Jordan Hall, 1001 E. 3rd St., Bloomington, IN, 47405, USA.,Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
| | - Adam R Smith
- Department of Biology, Indiana University, Jordan Hall, 1001 E. 3rd St., Bloomington, IN, 47405, USA.,Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
| | - Douglas B Rusch
- Department of Biology, Indiana University, Jordan Hall, 1001 E. 3rd St., Bloomington, IN, 47405, USA.,Center for Genomics and Bioinformatics, Indiana University, Bloomington, IN, 47405, USA
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