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Losilla M, Gallant JR. Molecular evolution of the ependymin-related gene epdl2 in African weakly electric fish. G3 (BETHESDA, MD.) 2023; 13:6931758. [PMID: 36529459 PMCID: PMC9997568 DOI: 10.1093/g3journal/jkac331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/01/2022] [Accepted: 11/16/2022] [Indexed: 12/23/2022]
Abstract
Gene duplication and subsequent molecular evolution can give rise to taxon-specific gene specializations. In previous work, we found evidence that African weakly electric fish (Mormyridae) may have as many as three copies of the epdl2 gene, and the expression of two epdl2 genes is correlated with electric signal divergence. Epdl2 belongs to the ependymin-related family (EPDR), a functionally diverse family of secretory glycoproteins. In this study, we first describe vertebrate EPDR evolution and then present a detailed evolutionary history of epdl2 in Mormyridae with emphasis on the speciose genus Paramormyrops. Using Sanger sequencing, we confirm three apparently functional epdl2 genes in Paramormyrops kingsleyae. Next, we developed a nanopore-based amplicon sequencing strategy and bioinformatics pipeline to obtain and classify full-length epdl2 gene sequences (N = 34) across Mormyridae. Our phylogenetic analysis proposes three or four epdl2 paralogs dating from early Paramormyrops evolution. Finally, we conducted selection tests which detected positive selection around the duplication events and identified ten sites likely targeted by selection in the resulting paralogs. These sites' locations in our modeled 3D protein structure involve four sites in ligand binding and six sites in homodimer formation. Together, these findings strongly imply an evolutionary mechanism whereby epdl2 genes underwent selection-driven functional specialization after tandem duplications in the rapidly speciating Paramormyrops. Considering previous evidence, we propose that epdl2 may contribute to electric signal diversification in mormyrids, an important aspect of species recognition during mating.
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Affiliation(s)
- Mauricio Losilla
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA.,Graduate Program in Ecology, Evolution and Behavior, Michigan State University, East Lansing, MI 48824, USA
| | - Jason R Gallant
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA.,Graduate Program in Ecology, Evolution and Behavior, Michigan State University, East Lansing, MI 48824, USA
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Intergenus F1-hybrids of African weakly electric fish (Mormyridae: Gnathonemus petersii ♂ × Campylomormyrus compressirostris ♀) are fertile. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2022; 208:355-371. [PMID: 35119505 PMCID: PMC9123046 DOI: 10.1007/s00359-022-01542-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 01/09/2022] [Accepted: 01/10/2022] [Indexed: 11/16/2022]
Abstract
Hybridisation is an important element of adaptive radiation in fish but data are limited in weakly electric mormyrid fish in this respect. Recently, it has been shown that intragenus hybrids (Campylomormyrus) are fertile and are able to produce F2-fish. In this paper, we demonstrate that even intergenus hybrids (Gnathonemus petersii ♂ × Campylomormyrus compressirostris ♀) are fertile. Three artificial reproduction (AR) trials, with an average fertilisation rate of ca. 23%, yielded different numbers of survivals (maximally about 50%) of the F1-hybrids. The complete ontogenetic development of these hybrids is described concerning their morphology and electric organ discharge (EOD). Two EOD types emerged at the juvenile stage, which did not change up to adulthood. Type I consisted of four phases and Type II was triphasic. The minimum body length at sexual maturity was between 10 and 11 cm. Malformations, growth and mortality rates are also described.
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Picq S, Sperling J, Cheng CJ, Carlson BA, Gallant JR. Genetic drift does not sufficiently explain patterns of electric signal variation among populations of the mormyrid electric fish Paramormyrops kingsleyae. Evolution 2020; 74:911-935. [PMID: 32187650 PMCID: PMC7816287 DOI: 10.1111/evo.13953] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 02/13/2020] [Accepted: 02/20/2020] [Indexed: 11/28/2022]
Abstract
Communication signals serve crucial survival and reproductive functions. In Gabon, the widely distributed mormyrid fish Paramormyrops kingsleyae emits an electric organ discharge (EOD) signal with a dual role in communication and electrolocation that exhibits remarkable variation: populations of P. kingsleyae have either biphasic or triphasic EODs, a feature that characterizes interspecific signal diversity among the Paramormyrops genus. We quantified variation in EODs of 327 P. kingsleyae from nine populations and compared it to genetic variation estimated from microsatellite loci. We found no correlation between electric signal and genetic distances, suggesting that EOD divergence cannot be explained by drift alone. An alternative hypothesis is that EOD differences are used for mate discrimination, which would require P. kingsleyae be capable of differentiating between divergent EOD waveforms. Using a habituation-dishabituation assay, we found that P. kingsleyae can discriminate between biphasic and triphasic EOD types. Nonetheless, patterns of genetic and electric organ morphology divergence provide evidence for hybridization between these signal types. Although reproductive isolation with respect to signal type is incomplete, our results suggest that EOD variation in P. kingsleyae could be a cue for assortative mating.
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Affiliation(s)
- Sophie Picq
- Michigan State University Department of Integrative Biology, East Lansing MI 48824 USA
| | - Joshua Sperling
- Cornell University Department of Neurobiology and Behavior, Ithaca NY 14853 USA
| | - Catherine J. Cheng
- Cornell University Department of Neurobiology and Behavior, Ithaca NY 14853 USA
| | - Bruce A. Carlson
- Washington University in St. Louis Department of Biology, St. Louis, MO 63130 USA
| | - Jason R. Gallant
- Michigan State University Department of Integrative Biology, East Lansing MI 48824 USA
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Ontogeny of electric organ and electric organ discharge in Campylomormyrus rhynchophorus (Teleostei: Mormyridae). J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2020; 206:453-466. [PMID: 32112119 PMCID: PMC8557190 DOI: 10.1007/s00359-020-01411-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 02/09/2020] [Accepted: 02/15/2020] [Indexed: 10/29/2022]
Abstract
The aim of this study was a longitudinal description of the ontogeny of the adult electric organ of Campylomormyrus rhynchophorus which produces as adult an electric organ discharge of very long duration (ca. 25 ms). We could indeed show (for the first time in a mormyrid fish) that the electric organ discharge which is first produced early during ontogeny in 33-mm-long juveniles is much shorter in duration and has a different shape than the electric organ discharge in 15-cm-long adults. The change from this juvenile electric organ discharges into the adult electric organ discharge takes at least a year. The increase in electric organ discharge duration could be causally linked to the development of surface evaginations, papillae, at the rostral face of the electrocyte which are recognizable for the first time in 65-mm-long juveniles and are most prominent at the periphery of the electrocyte.
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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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6
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Losilla M, Luecke DM, Gallant JR. The transcriptional correlates of divergent electric organ discharges in Paramormyrops electric fish. BMC Evol Biol 2020; 20:6. [PMID: 31918666 PMCID: PMC6953315 DOI: 10.1186/s12862-019-1572-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 12/24/2019] [Indexed: 01/10/2023] Open
Abstract
Background Understanding the genomic basis of phenotypic diversity can be greatly facilitated by examining adaptive radiations with hypervariable traits. In this study, we focus on a rapidly diverged species group of mormyrid electric fish in the genus Paramormyrops, which are characterized by extensive phenotypic variation in electric organ discharges (EODs). The main components of EOD diversity are waveform duration, complexity and polarity. Using an RNA-sequencing based approach, we sought to identify gene expression correlates for each of these EOD waveform features by comparing 11 specimens of Paramormyrops that exhibit variation in these features. Results Patterns of gene expression among Paramormyrops are highly correlated, and 3274 genes (16%) were differentially expressed. Using our most restrictive criteria, we detected 145–183 differentially expressed genes correlated with each EOD feature, with little overlap between them. The predicted functions of several of these genes are related to extracellular matrix, cation homeostasis, lipid metabolism, and cytoskeletal and sarcomeric proteins. These genes are of significant interest given the known morphological differences between electric organs that underlie differences in the EOD waveform features studied. Conclusions In this study, we identified plausible candidate genes that may contribute to phenotypic differences in EOD waveforms among a rapidly diverged group of mormyrid electric fish. These genes may be important targets of selection in the evolution of species-specific differences in mate-recognition signals.
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Affiliation(s)
- Mauricio Losilla
- Department of Integrative Biology, Michigan State University, East Lansing, MI, 48824, USA.,Graduate Program in Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, 48824, USA
| | - David Michael Luecke
- Department of Integrative Biology, Michigan State University, East Lansing, MI, 48824, USA.,Graduate Program in Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, 48824, USA
| | - Jason R Gallant
- Department of Integrative Biology, Michigan State University, East Lansing, MI, 48824, USA. .,Graduate Program in Ecology, Evolutionary Biology and Behavior, Michigan State University, East Lansing, MI, 48824, USA.
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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: 64] [Impact Index Per Article: 12.8] [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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Gallant JR, Losilla M, Tomlinson C, Warren WC. The Genome and Adult Somatic Transcriptome of the Mormyrid Electric Fish Paramormyrops kingsleyae. Genome Biol Evol 2017; 9:3525-3530. [PMID: 29240929 PMCID: PMC5751062 DOI: 10.1093/gbe/evx265] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/11/2017] [Indexed: 12/23/2022] Open
Abstract
Several studies have begun to elucidate the genetic and developmental processes underlying major vertebrate traits. Few of these traits have evolved repeatedly in vertebrates, preventing the analysis of molecular mechanisms underlying these traits comparatively. Electric organs have evolved multiple times among vertebrates, presenting a unique opportunity to understand the degree of constraint and repeatability of the evolutionary processes underlying novel vertebrate traits. As there is now a completed genome sequence representing South American electric eels, we were motivated to obtain genomic sequence from a linage that independently evolved electric organs to facilitate future comparative analyses of the evolution and development of electric organs. We report here the sequencing and de novo assembly of the genome of the mormyrid Paramormyrops kingsleyae using short-read sequencing. In addition, we have completed a somatic transcriptome from 11 tissues to construct a gene expression atlas of predicted genes from this assembly, enabling us to identify candidate housekeeping genes as well as genes differentially expressed in the major somatic tissues of the mormyrid electric fish. We anticipate that this resource will greatly facilitate comparative studies on the evolution and development of electric organs and electroreceptors.
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Affiliation(s)
- Jason R Gallant
- Department of Integrative Biology, Michigan State University
| | | | - Chad Tomlinson
- McDonnell Genome Institute, Washington University, St Louis
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Kirschbaum F, Nguyen L, Baumgartner S, Chi HWL, Wolfart R, Elarbani K, Eppenstein H, Korniienko Y, Guido-Böhm L, Mamonekene V, Vater M, Tiedemann R. Intragenus (Campylomormyrus) and intergenus hybrids in mormyrid fish: Physiological and histological investigations of the electric organ ontogeny. ACTA ACUST UNITED AC 2017; 110:281-301. [PMID: 28108418 DOI: 10.1016/j.jphysparis.2017.01.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 01/04/2017] [Accepted: 01/14/2017] [Indexed: 11/24/2022]
Abstract
African weakly electric mormyrid fish show a high diversity of their electric organ discharge (EOD) both across and within genera. Thanks to a recently developed technique of artificial reproduction in mormyrid fish, we were able to perform hybridizations between different genera and within one genus (Campylomormyrus). The hybrids of intergenus hybridizations exhibited different degrees of reduced survival related to the phylogenetic distance of the parent species: hybrids of the crosses between C. rhynchophorus and its sister genus Gnathonemus survived and developed normally. Hybrids between C. rhynchophorus and a Mormyrus species (a more basal clade compared to Campylomormyrus s) survived up to 42days and developed many malformations, e.g., at the level of the unpaired fins. Hybrids between C. numenius and Hippopotamyrus pictus (a derived clade, only distantly related to Campylomormyrus) only survived for two days during embryological development. Eight different hybrid combinations among five Campylomormyrus species (C. tamandua, C. compressirostris, C. tshokwe, C. rhynchophorus, C. numenius) were performed. The aim of the hybridizations was to combine species with (1) either caudal or rostral position of the main stalk innervating the electrocytes in the electric organ and (2) short, median or long duration of their EOD. The hybrids, though they are still juveniles, show very interesting features concerning electrocyte geometry as well as EOD form and duration: the caudal position of the stalk is prevailing over the rostral position, and the penetration of the stalk is dominant over the non-penetrating feature (in the Campylomormyrus hybrids); in the hybrid between C. rhynchophorus and Gnathonemus petersii it is the opposite. When crossing species with long and short EODs, it is always the long duration EOD that is expressed in the hybrids. The F1-Hybrids of the cross C. tamandua×C. compressirostris are fertile: viable F2-fish could be obtained with artificial reproduction.
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Affiliation(s)
- Frank Kirschbaum
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany.
| | - Linh Nguyen
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany; University of Potsdam, Institute of Biochemistry and Biology, Unit of Evolutionary Biology/Systematic Zoology, Karl-Liebknecht-Str. 24-25, Haus 26, D-14476 Potsdam-Golm, Germany
| | - Stephanie Baumgartner
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany
| | - Hiu Wan Linda Chi
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany
| | - Rene Wolfart
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany
| | - Khouloud Elarbani
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany
| | - Hari Eppenstein
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany
| | - Yevheniia Korniienko
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany
| | - Lilian Guido-Böhm
- Humboldt University, Faculty of Life Sciences, Unit of Biology and Ecology of Fishes, Philippstr. 13, Haus 16, D-10115 Berlin, Germany
| | - Victor Mamonekene
- Ecole Nationale Supérieure d'Agronomie et de Foresterie, Université Marien Ngouabi, B.P. 69, Brazzaville, People's Republic of Congo
| | - Marianne Vater
- University of Potsdam, Institute of Biochemistry and Biology, Unit of General Zoology, Karl-Liebknecht-Str. 24-25, Haus 26, D-14476 Potsdam-Golm, Germany
| | - Ralph Tiedemann
- University of Potsdam, Institute of Biochemistry and Biology, Unit of Evolutionary Biology/Systematic Zoology, Karl-Liebknecht-Str. 24-25, Haus 26, D-14476 Potsdam-Golm, Germany
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10
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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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11
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Lamanna F, Kirschbaum F, Ernst AR, Feulner PG, Mamonekene V, Paul C, Tiedemann R. Species delimitation and phylogenetic relationships in a genus of African weakly-electric fishes (Osteoglossiformes, Mormyridae, Campylomormyrus). Mol Phylogenet Evol 2016; 101:8-18. [DOI: 10.1016/j.ympev.2016.04.035] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 04/26/2016] [Accepted: 04/29/2016] [Indexed: 11/30/2022]
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12
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Lavoué S, Sullivan JP. Petrocephalus boboto and Petrocephalus arnegardi, two new species of African electric fish (Osteoglossomorpha, Mormyridae) from the Congo River basin. Zookeys 2014:43-65. [PMID: 24843255 PMCID: PMC4023242 DOI: 10.3897/zookeys.400.6743] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 03/26/2014] [Indexed: 11/23/2022] Open
Abstract
A specimen of the African weakly electric fish genus Petrocephalus (Osteoglossomorpha, Mormyridae) collected in the Congo River at Yangambi, Orientale Province, Democratic Republic of Congo, is described as a new species. Petrocephalus bobotosp. n. can be distinguished from other Central African species of Petrocephalus by a combination of the following characteristics: three distinct black spots on the body, one at the origin of the pectoral fin, one at the origin of the caudal fin and one below the anterior base of the dorsal fin; Nakenrosette and Khelrosette electroreceptor clusters distinct on head but Augenrosette cluster reduced in size; 23 branched dorsal rays, 34 branched anal rays, and electric organ discharge waveform triphasic. Petrocephalus bobotosp. n. most closely resembles the holotype of Petrocephalus binotatus but is easily distinguished from it by its smaller mouth. A comparative molecular analysis including 21 other Petrocephalus species shows Petrocephalus bobotosp. n. to be genetically distinctive and to represent a deep lineage in the genus. Two specimens of Petrocephalus collected at Yangambi are morphologically similar and genetically closely related to specimens previously assigned to Petrocephalus binotatus, collected in the northwestern Congo River basin within Odzala-Kokua National Park, Republic of the Congo. This prompts us to formally describe a new species from these collections, Petrocephalus arnegardisp. n., that, although similar to the holotype of Petrocephalus binotatus, can be distinguished from it by its smaller mouth and shorter interorbital width.
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Affiliation(s)
- Sébastien Lavoué
- Institute of Oceanography, National Taiwan University, Roosevelt Road, Taipei 10617, Taiwan
| | - John P Sullivan
- Cornell University Museum of Vertebrates, 159 Sapsucker Woods Road, Ithaca, New York 14850 USA
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13
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Kramer B, van der Bank H, Wink M. Marked differentiation in a new species of dwarf stonebasher,Pollimyrus cuandoensissp. nov. (Mormyridae: Teleostei), from a contact zone with two sibling species of the Okavango and Zambezi rivers. J NAT HIST 2013. [DOI: 10.1080/00222933.2013.807950] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Carlson BA, Gallant JR. From sequence to spike to spark: evo-devo-neuroethology of electric communication in mormyrid fishes. J Neurogenet 2013; 27:106-29. [PMID: 23802152 DOI: 10.3109/01677063.2013.799670] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mormyrid fishes communicate using pulses of electricity, conveying information about their identity, behavioral state, and location. They have long been used as neuroethological model systems because they are uniquely suited to identifying cellular mechanisms for behavior. They are also remarkably diverse, and they have recently emerged as a model system for studying how communication systems may influence the process of speciation. These two lines of inquiry have now converged, generating insights into the neural basis of evolutionary change in behavior, as well as the influence of sensory and motor systems on behavioral diversification and speciation. Here, we review the mechanisms of electric signal generation, reception, and analysis and relate these to our current understanding of the evolution and development of electromotor and electrosensory systems. We highlight the enormous potential of mormyrids for studying evolutionary developmental mechanisms of behavioral diversification, and make the case for developing genomic and transcriptomic resources. A complete mormyrid genome sequence would enable studies that extend our understanding of mormyrid behavior to the molecular level by linking morphological and physiological mechanisms to their genetic basis. Applied in a comparative framework, genomic resources would facilitate analysis of evolutionary processes underlying mormyrid diversification, reveal the genetic basis of species differences in behavior, and illuminate the origins of a novel vertebrate sensory and motor system. Genomic approaches to studying the evo-devo-neuroethology of mormyrid communication represent a deeply integrative approach to understanding the evolution, function, development, and mechanisms of behavior.
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Affiliation(s)
- Bruce A Carlson
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri 63130-4899, USA.
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15
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Feulner PG, Plath M, Engelmann J, Kirschbaum F, Tiedemann R. Magic trait electric organ discharge (EOD): Dual function of electric signals promotes speciation in African weakly electric fish. Commun Integr Biol 2013; 2:329-31. [PMID: 19721881 DOI: 10.4161/cib.2.4.8386] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 03/11/2009] [Indexed: 11/19/2022] Open
Abstract
A unique evolutionary specialization of African weakly electric fish (Mormyridae) is their ability to produce and perceive electric signals. Mormyrids use their electric organs discharge (EOD) for electrolocation and electrocommunication. Here we discuss the adaptive significance of the EOD in foraging (electric prey detection) in light of recent results demonstrating that mormyrid fish mate assortatively according to EOD waveform characteristics (electric mate choice). Therefore the EOD as a single trait pleiotropically combines natural divergent selection and reproductive isolation. Consequently we postulate the EOD as a "magic trait" promoting the diversification of African weakly electric fish.
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Affiliation(s)
- Philine Gd Feulner
- Institute of Biochemistry and Biology; University of Potsdam; Potsdam, Germany
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Lyons-Warren AM, Hollmann M, Carlson BA. Sensory receptor diversity establishes a peripheral population code for stimulus duration at low intensities. ACTA ACUST UNITED AC 2012; 215:2586-600. [PMID: 22786635 DOI: 10.1242/jeb.064733] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Peripheral filtering is a fundamental mechanism for establishing frequency tuning in sensory systems. By contrast, detection of temporal features, such as duration, is generally thought to result from temporal coding in the periphery, followed by an analysis of peripheral response times within the central nervous system. We investigated how peripheral filtering properties affect the coding of stimulus duration in the electrosensory system of mormyrid fishes using behavioral and electrophysiological measures of duration tuning. We recorded from individual knollenorgans, the electrosensory receptors that mediate communication, and found correlated variation in frequency tuning and duration tuning, as predicted by a simple circuit model. In response to relatively high intensity stimuli, knollenorgans responded reliably with fixed latency spikes, consistent with a temporal code for stimulus duration. At near-threshold intensities, however, both the reliability and the temporal precision of responses decreased. Evoked potential recordings from the midbrain, as well as behavioral responses to electrosensory stimulation, revealed changes in sensitivity across the range of durations associated with the greatest variability in receptor sensitivity. Further, this range overlapped with the natural range of variation in species-specific communication signals, suggesting that peripheral duration tuning affects the coding of behaviorally relevant stimuli. We measured knollenorgan, midbrain and behavioral responses to natural communication signals and found that each of them were duration dependent. We conclude that at relatively low intensities for which temporal coding is ineffective, diversity among sensory receptors establishes a population code, in which duration is reflected in the population of responding knollenorgans.
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Affiliation(s)
- Ariel M Lyons-Warren
- Department of Biology, Washington University in St Louis, St Louis, MO 63130-4899, USA
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17
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Carlson BA, Arnegard ME. Neural innovations and the diversification of African weakly electric fishes. Commun Integr Biol 2012; 4:720-5. [PMID: 22446537 DOI: 10.4161/cib.17483] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In African mormyrid fishes, evolutionary change in a sensory region of the brain established an ability to detect subtle variation in electric communication signals. In one lineage, this newfound perceptual ability triggered a dramatic increase in the rates of signal evolution and species diversification. This particular neural innovation is just one in a series of nested evolutionary novelties that characterize the sensory and motor systems of mormyrids, the most speciose group of extant osteoglossomorph fishes. Here we discuss the behavioral significance of these neural innovations, relate them to differences in extant species diversity, and outline possible scenarios by which some of these traits may have fueled diversification. We propose that sensory and motor capabilities limit the extent to which signals evolve and, by extension, the role of communication behavior in the process of speciation. By expanding these capabilities, neural innovations increase the potential for signal evolution and species diversification.
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18
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Horth L, Panayotova IN. Simulating the maintenance of a rare fish morph experiencing negative frequency dependent selection. Biosystems 2012; 110:149-55. [PMID: 23025992 DOI: 10.1016/j.biosystems.2012.08.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Revised: 08/14/2012] [Accepted: 08/25/2012] [Indexed: 10/27/2022]
Abstract
Empirical work assessing the maintenance of rare genotypes in natural populations is difficult over very long time scales. Skirting this problematic issue is possible with theory and simulations. Major theoretical constructs, including mutation-selection balance and balancing selection, explain the theoretical maintenance of rare genotypes, and the occurrence of multiple, rare genotypes over time. Additionally, numerical simulations are valuable tools for assessing evolving biological systems because they allow for monitoring systems over long time scales, as well as for controlling model parameters, thus contributing to the exploration of system dynamics that cannot be assessed in nature. Here we employed numerical simulations to explore the importance of several biological factors that contribute to the maintenance of a fish color-pattern polymorphism. We present a numerical model of a two-morph fish polymorphism that allowed us to test the sensitivity of the rare morph's persistence and the population's stability to multiple parameters. Our simulations ran over 10,000 years (where one year is approximately one generation) and demonstrated the maintenance of a stable polymorphism with a rare morph which persisted at a frequency of ~10(-2), which is in-fact the frequency of the rare, mottled black mosquitofish morph in natural populations. This pigmentation polymorphism is stable, independent of changes in population size, but can be destabilized with very high predation when coupled with very low birth rates. Employing models with empirical fitness estimates is a valuable tool for monitoring rare vertebrate morphs in nature, however few studies exist that have accomplished this task. Our approach can be adapted for modeling rare morphs (particularly in additional live-bearing fishes like sailfin mollies) that also harbor rare, pigmentation morphs within large populations.
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Affiliation(s)
- Lisa Horth
- Department of Biology, 4700 Elkhorn Ave Old Dominion University, Norfolk, VA 23529, USA.
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19
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Lavoué S, Miya M, Arnegard ME, Sullivan JP, Hopkins CD, Nishida M. Comparable ages for the independent origins of electrogenesis in African and South American weakly electric fishes. PLoS One 2012; 7:e36287. [PMID: 22606250 PMCID: PMC3351409 DOI: 10.1371/journal.pone.0036287] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 03/29/2012] [Indexed: 11/26/2022] Open
Abstract
One of the most remarkable examples of convergent evolution among vertebrates is illustrated by the independent origins of an active electric sense in South American and African weakly electric fishes, the Gymnotiformes and Mormyroidea, respectively. These groups independently evolved similar complex systems for object localization and communication via the generation and reception of weak electric fields. While good estimates of divergence times are critical to understanding the temporal context for the evolution and diversification of these two groups, their respective ages have been difficult to estimate due to the absence of an informative fossil record, use of strict molecular clock models in previous studies, and/or incomplete taxonomic sampling. Here, we examine the timing of the origins of the Gymnotiformes and the Mormyroidea using complete mitogenome sequences and a parametric bayesian method for divergence time reconstruction. Under two different fossil-based calibration methods, we estimated similar ages for the independent origins of the Mormyroidea and Gymnotiformes. Our absolute estimates for the origins of these groups either slightly postdate, or just predate, the final separation of Africa and South America by continental drift. The most recent common ancestor of the Mormyroidea and Gymnotiformes was found to be a non-electrogenic basal teleost living more than 85 millions years earlier. For both electric fish lineages, we also estimated similar intervals (16-19 or 22-26 million years, depending on calibration method) between the appearance of electroreception and the origin of myogenic electric organs, providing rough upper estimates for the time periods during which these complex electric organs evolved de novo from skeletal muscle precursors. The fact that the Gymnotiformes and Mormyroidea are of similar age enhances the comparative value of the weakly electric fish system for investigating pathways to evolutionary novelty, as well as the influences of key innovations in communication on the process of species radiation.
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Affiliation(s)
- Sébastien Lavoué
- Institute of Oceanography, National Taiwan University, Taipei, Taiwan.
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20
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Abstract
Populations that have independently evolved reproductive isolation from their ancestors while remaining reproductively cohesive have undergone parallel speciation. A specific type of parallel speciation, known as parallel ecological speciation, is one of several forms of evidence for ecology's role in speciation. In this paper we search the literature for candidate examples of parallel ecological speciation in plants. We use four explicit criteria (independence, isolation, compatibility, and selection) to judge the strength of evidence for each potential case. We find that evidence for parallel ecological speciation in plants is unexpectedly scarce, especially relative to the many well-characterized systems in animals. This does not imply that ecological speciation is uncommon in plants. It only implies that evidence from parallel ecological speciation is rare. Potential explanations for the lack of convincing examples include a lack of rigorous testing and the possibility that plants are less prone to parallel ecological speciation than animals.
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21
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Carlson BA, Hasan SM, Hollmann M, Miller DB, Harmon LJ, Arnegard ME. Brain Evolution Triggers Increased Diversification of Electric Fishes. Science 2011; 332:583-6. [DOI: 10.1126/science.1201524] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Gallant JR, Arnegard ME, Sullivan JP, Carlson BA, Hopkins CD. Signal variation and its morphological correlates in Paramormyrops kingsleyae provide insight into the evolution of electrogenic signal diversity in mormyrid electric fish. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2011; 197:799-817. [PMID: 21505877 DOI: 10.1007/s00359-011-0643-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 03/18/2011] [Accepted: 03/23/2011] [Indexed: 11/26/2022]
Abstract
We describe patterns of geographic variation in electric signal waveforms among populations of the mormyrid electric fish species Paramormyrops kingsleyae. This analysis includes study of electric organs and electric organ discharge (EOD) signals from 553 specimens collected from 12 localities in Gabon, West-Central Africa from 1998 to 2009. We measured time, slope, and voltage values from nine defined EOD "landmarks" and determined peak spectral frequencies from each waveform; these data were subjected to principal components analysis. The majority of variation in EODs is explained by two factors: the first related to EOD duration, the second related to the magnitude of the weak head-negative pre-potential, P0. Both factors varied clinally across Gabon. EODs are shorter in eastern Gabon and longer in western Gabon. Peak P0 is slightly larger in northern Gabon and smaller in southern Gabon. P0 in the EOD is due to the presence of penetrating-stalked (Pa) electrocytes in the electric organ while absence is due to the presence of non-penetrating stalked electrocytes (NPp). Across Gabon, the majority of P. kingsleyae populations surveyed have only individuals with P0-present EODs and Pa electrocytes. We discovered two geographically distinct populations, isolated from others by barriers to migration, where all individuals have P0-absent EODs with NPp electrocytes. At two sites along a boundary between P0-absent and P0-present populations, P0-absent and P0-present individuals were found in sympatry; specimens collected there had electric organs of intermediate morphology. This pattern of geographic variation in EODs is considered in the context of current phylogenetic work. Multiple independent paedomorphic losses of penetrating stalked electrocytes have occurred within five Paramormyrops species and seven genera of mormyrids. We suggest that this key anatomical feature in EOD signal evolution may be under a simple mechanism of genetic control, and may be easily influenced by selection or drift throughout the evolutionary history of mormyrids.
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Affiliation(s)
- Jason R Gallant
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, USA.
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23
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Crampton WGR, Lovejoy NR, Waddell JC. Reproductive character displacement and signal ontogeny in a sympatric assemblage of electric fish. Evolution 2011; 65:1650-66. [PMID: 21644955 DOI: 10.1111/j.1558-5646.2011.01245.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The reproductive signals of two or more taxa may diverge in areas of sympatry, due to selection against costly reproductive interference. This divergence, termed reproductive character displacement (RCD), is expected in species-rich assemblages, where interspecific signal partitioning among closely related species is common. However, RCD is usually documented from simple two-taxon cases, via geographical tests for greater divergence of reproductive traits in sympatry than in allopatry. We propose a novel approach to recognizing and understanding RCD in multi-species communities--one that traces the displacement of signals within multivariate signal space during the ontogeny of individual animals. We argue that a case for RCD can be made if the amount of signal displacement between a pair of species after maturation is negatively correlated to distance in signal space before maturation. Our application of this approach, using a dataset of communication signals from a sympatric Amazonian assemblage of the electric fish genus Gymnotus, provides strong evidence for RCD among multiple species. We argue that RCD arose from the costs of heterospecific mismating, but interacted with sexual selection--favoring the evolution of conspicuous male signals that not only serve for mate-choice, but which simultaneously facilitate species recognition.
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Affiliation(s)
- William G R Crampton
- Department of Biology, University of Central Florida, 4000 Central Florida Boulevard, Orlando, 32816-2368 Florida, USA.
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24
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Communication in troubled waters: responses of fish communication systems to changing environments. Evol Ecol 2010. [DOI: 10.1007/s10682-010-9450-x] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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25
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Arnegard ME, McIntyre PB, Harmon LJ, Zelditch ML, Crampton WGR, Davis JK, Sullivan JP, Lavoué S, Hopkins CD. Sexual signal evolution outpaces ecological divergence during electric fish species radiation. Am Nat 2010; 176:335-56. [PMID: 20653442 DOI: 10.1086/655221] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Natural selection arising from resource competition and environmental heterogeneity can drive adaptive radiation. Ecological opportunity facilitates this process, resulting in rapid divergence of ecological traits in many celebrated radiations. In other cases, sexual selection is thought to fuel divergence in mating signals ahead of ecological divergence. Comparing divergence rates between naturally and sexually selected traits can offer insights into processes underlying species radiations, but to date such comparisons have been largely qualitative. Here, we quantitatively compare divergence rates for four traits in African mormyrid fishes, which use an electrical communication system with few extrinsic constraints on divergence. We demonstrate rapid signal evolution in the Paramormyrops species flock compared to divergence in morphology, size, and trophic ecology. This disparity in the tempo of trait evolution suggests that sexual selection is an important early driver of species radiation in these mormyrids. We also found slight divergence in ecological traits among closely related species, consistent with a supporting role for natural selection in Paramormyrops diversification. Our results highlight the potential for sexual selection to drive explosive signal divergence when innovations in communication open new opportunities in signal space, suggesting that opportunity can catalyze species radiations through sexual selection, as well as natural selection.
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Affiliation(s)
- Matthew E Arnegard
- Department of Zoology, University of British Columbia, Vancouver, Canada.
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26
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Kramer B, Swartz ER. A new species of Slender Stonebasher within theHippopotamyrus ansorgiicomplex from the Cunene River in southern Africa (Teleostei: Mormyriformes). J NAT HIST 2010. [DOI: 10.1080/00222931003764089] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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27
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Abstract
Weakly electric fishes emit electric organ discharges (EODs) from their tail electric organs and sense feedback signals from their EODs by electroreceptors in the skin. The electric sense is utilized for various behaviors, including electrolocation, electrocommunication, and the Jamming avoidance response (JAR). For each behavior, various types of sensory Information are embedded in the transient electrical signals produced by the fish. These temporal signals are sampled, encoded, and further processed by peripheral and central neurons specialized for time coding. There are time codes for the sex or species Identities of other fish or the resistance and capacitance of objects. In the central nervous system, specialized neural elements exist for decoding time codes for different behavioral functions. Comparative studies allow phylogenetic comparison of time-coding neural systems among weakly electric fishes.
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Affiliation(s)
- Masashi Kawasaki
- Department of Biology, Gilmer Hall, University of Virginia, Charlottesville, VA 22904, USA.
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28
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Moritz T, Engelmann J, Linsenmair KE, von der Emde G. The electric organ discharges of the Petrocephalus species (Teleostei: Mormyridae) of the Upper Volta system. JOURNAL OF FISH BIOLOGY 2009; 74:54-76. [PMID: 20735524 DOI: 10.1111/j.1095-8649.2008.02111.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In this study, a first comparative investigation of all four species of Petrocephalus (P. bovei, P. bane, P. soudanensis and P. cf. pallidomaculatus) present in the Upper Volta system and their electric organ discharges (EOD) was conducted. It was found that P. bovei was the most widespread (in terms of habitat use), but in several places P. bovei, P. soudanensis and P. cf. pallidomaculatus occurred syntopically. All species emitted a triphasic signal, and with very few exceptions, the Petrocephalus species of the Upper Volta system could clearly be identified on the basis of their EOD waveforms. The most obvious differences between species in EOD waveforms were in amplitude of the last phase, total duration and fast Fourier transformation (FFT) peak frequency. No sexual dimorphism was present in the EOD of any species although external dimorphism, i.e. an indentation at the base of the anal fin of mature males, was common. The EOD waveform diversity in the Upper Volta principally resembled that found in four sympatric Petrocephalus species from the Ogooué system (Gabon) and might play a role in species recognition and speciation processes.
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Affiliation(s)
- T Moritz
- Lehrstuhl für Tierökologie und Tropenbiologie (Zoologie III), Theodor-Boveri-Institut (Biozentrum), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany.
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29
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Crampton WGR, Davis JK, Lovejoy NR, Pensky M. Multivariate classification of animal communication signals: a simulation-based comparison of alternative signal processing procedures using electric fishes. ACTA ACUST UNITED AC 2008; 102:304-21. [PMID: 18984042 DOI: 10.1016/j.jphysparis.2008.10.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Evolutionary studies of communication can benefit from classification procedures that allow individual animals to be assigned to groups (e.g. species) on the basis of high-dimension data representing their signals. Prior to classification, signals are usually transformed by a signal processing procedure into structural features. Applications of these signal processing procedures to animal communication have been largely restricted to the manual or semi-automated identification of landmark features from graphical representations of signals. Nonetheless, theory predicts that automated time-frequency-based digital signal processing (DSP) procedures can represent signals more efficiently (using fewer features) than can landmark procedures or frequency-based DSP - allowing more accurate classification. Moreover, DSP procedures are objective in that they require little previous knowledge of signal diversity, and are relatively free from potentially ungrounded assumptions of cross-taxon homology. Using a model data set of electric organ discharge waveforms from five sympatric species of the electric fish Gymnotus, we adopted an exhaustive simulation approach to investigate the classificatory performance of different signal processing procedures. We considered a landmark procedure, a frequency-based DSP procedure (the fast Fourier transform), and two kinds of time-frequency-based DSP procedures (a short-time Fourier transform, and several implementations of the discrete wavelet transform -DWT). The features derived from each of these signal processing procedures were then subjected to dimension reduction procedures to separate those features which permit the most effective discrimination among groups of signalers. We considered four alternative dimension reduction methods. Finally, each combination of reduced data was submitted to classification by linear discriminant analysis. Our results support theoretical predictions that time-frequency DSP procedures (especially DWT) permit more efficient discrimination of groups. The performance of signal processing was found to depend largely upon the dimension reduction procedure employed, and upon the number of resulting features. Because the best combinations of procedures are dataset-dependent and difficult to predict, we conclude that simulations of the kind described here, or at least simplified versions of them, should be routinely executed before classification of animal signals - especially unfamiliar ones.
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Affiliation(s)
- William G R Crampton
- Department of Biology, University of Central Florida, Orlando, FL 32816-2368, USA.
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30
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Adaptive radiation in the Congo River: an ecological speciation scenario for African weakly electric fish (Teleostei; Mormyridae; Campylomormyrus). ACTA ACUST UNITED AC 2008; 102:340-6. [PMID: 18984043 DOI: 10.1016/j.jphysparis.2008.10.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ultimate aim of this study is to better understand the diversification of African weakly electric fish in the Congo River. Based on a robust phylogenetic hypothesis we examined the radiation within the mormyrid genus Campylomormyrus. Morphological traits relevant for the divergence between the identified species were detected. Among them, the variation in the shape of the trunk-like elongated snout suggested the presence of different trophic specializations. Furthermore, the chosen model taxon, the genus Campylomormyrus, exhibits a wide diversity of electric organ discharge (EOD) waveforms. A comparison of EOD waveform types and phylogenetic relationships showed major differences in EOD between closely related species. This indicates that the EOD might function as a reproductive isolation mechanism. In conclusion, we provide a plausible scenario of an adaptive radiation triggered by sexual selection and assortative mating based on EOD characteristics, but caused by a divergent selection on the feeding apparatus. These findings point towards an adaptive radiation of at least some Campylomormyrus species occurring in the Lower Congo River.
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31
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Lavoué S, Arnegard ME, Sullivan JP, Hopkins CD. Petrocephalus of Odzala offer insights into evolutionary patterns of signal diversification in the Mormyridae, a family of weakly electrogenic fishes from Africa. ACTA ACUST UNITED AC 2008; 102:322-39. [PMID: 18992333 DOI: 10.1016/j.jphysparis.2008.10.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Electric signals of mormyrid fishes have recently been described from several regions of Africa. Members of the Mormyridae produce weak electric organ discharges (EODs) as part of a specialized electrosensory communication and orientation system. Sympatric species often express distinctive EODs, which may contribute to species recognition during mate choice in some lineages. Striking examples of interspecific EOD variation within assemblages have been reported for two monophyletic radiations: the Paramormyrops of Gabon and the Campylomormyrus of Lower Congo. Here, we describe a speciose assemblage of Petrocephalus in the Lékoli River system of Odzala National Park, Republic of Congo. This widespread genus comprises the subfamily (Petrocephalinae) that is the sister group to all other mormyrids (Mormyrinae). Eleven Petrocephalus species were collected in Odzala, five of which are not described taxonomically. We quantify EOD variation within this assemblage and show that all eleven species produce EOD waveforms of brief duration (species means range from 144 to 663mus) compared to many other mormyrids. We also present reconstructed phylogenetic relationships among species based on cytochrome b sequences. Discovery of the Odzala assemblage greatly increases the number of Petrocephalus species for which EODs and DNA sequence data are available, permitting a first qualitative comparison between mormyrid subfamilies of the divergence patterns that have been described within lineages. We find that the Petrocephalus assemblage in Odzala is not a monophyletic radiation. Genetic divergence among Petrocephalus species often appears higher than among Paramormyrops or Campylomormyrus species. In contrast, results of this study and others suggest that Petrocephalus may generally exhibit less interspecific EOD divergence, as well as smaller sex differences in EOD waveforms, compared to Paramormyrops and Campylomormyrus. We discuss possible causes and consequences of EOD diversification patterns observed within mormyrid subfamilies as a framework for future comparative studies of signal evolution using this emerging model system.
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Affiliation(s)
- Sébastien Lavoué
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
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32
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Krahe R. Rooted in behaviour. ACTA ACUST UNITED AC 2008; 102:154-6. [PMID: 18992331 DOI: 10.1016/j.jphysparis.2008.10.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Weakly electric fish have been one of the most successful systems in which to study the neural basis of behaviour. Currently, three avenues of research hold particular promise: the combination of field and laboratory studies to improve our understanding of natural electrosensory stimuli and their role in behaviour; the integration of research on natural electrosensory scenes and sensory processing; multidisciplinary approaches to address questions of sensory processing and motor control.
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33
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Lavoué S, Sullivan JP, Arnegard ME, Hopkins CD. Differentiation of morphology, genetics and electric signals in a region of sympatry between sister species of African electric fish (Mormyridae). J Evol Biol 2008; 21:1030-45. [PMID: 18513358 DOI: 10.1111/j.1420-9101.2008.01544.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Mormyrid fishes produce and sense weak electric organ discharges (EODs) for object detection and communication, and they have been increasingly recognized as useful model organisms for studying signal evolution and speciation. EOD waveform variation can provide important clues to sympatric species boundaries between otherwise similar or morphologically cryptic forms. Endemic to the watersheds of Gabon (Central Africa), Ivindomyrus marchei and Ivindomyrus opdenboschi are morphologically similar to one another. Using morphometric, electrophysiological and molecular characters [cytochrome b sequences and amplified fragment length polymorphism (AFLP) genotypes], we investigated to what extent these nominal mormyrid species have diverged into biological species. Our sampling covered the known distribution of each species with a focus on the Ivindo River, where the two taxa co-occur. An overall pattern of congruence among datasets suggests that I. opdenboschi and I. marchei are mostly distinct. Electric signal analysis showed that EODs of I. opdenboschi tend to have a smaller initial head-positive peak than those of I. marchei, and they often possess a small third waveform peak that is typically absent in EODs of I. marchei. Analysis of sympatric I. opdenboschi and I. marchei populations revealed slight, but significant, genetic partitioning between populations based on AFLP data (F(ST) approximately 0.04). Taken separately, however, none of the characters we evaluated allowed us to discriminate two completely distinct or monophyletic groups. Lack of robust separation on the basis of any single character set may be a consequence of incomplete lineage sorting due to recent ancestry and/or introgressive hybridization. Incongruence between genetic datasets in one individual, which exhibited a mitochondrial haplotype characteristic of I. marchei but nevertheless fell within a genetic cluster of I. opdenboschi based on AFLP genotypes, suggests that a low level of recent hybridization may also be contributing to patterns of character variation in sympatry. Nevertheless, despite less than perfect separability based on any one dataset and inconclusive evidence for complete reproductive isolation between them in the Ivindo River, we find sufficient evidence to support the existence of two distinctive species, I. opdenboschi and I. marchei, even if not 'biological species' in the Mayrian sense.
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Affiliation(s)
- S Lavoué
- Department of Neurobiology and Behavior, W263 Seeley G. Mudd Hall, Cornell University, Ithaca, NY, USA.
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34
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MORITZ TIMO, LINSENMAIR KEDUARD, VON DER EMDE GERHARD. Electric organ discharge variability of Mormyridae (Teleostei: Osteoglossomorpha) in the Upper Volta system. Biol J Linn Soc Lond 2008. [DOI: 10.1111/j.1095-8312.2008.00956.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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35
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Abstract
Genetic diversity in species is often high in spite of directional selection or strong genetic drift. One resolution to this paradox may be through fitness benefits arising from interactions of genetically diverse individuals. Advantageous phenotypes that are impossible in single individuals (e.g. being simultaneously bold and shy) can be expressed by groups composed of genetically different individuals. Genetic diversity, therefore, can produce mutualistic benefits shared by all group members. We define this effect as 'social heterosis', and mathematically demonstrate maintenance of allelic diversity when diverse groups or neighbourhoods are more reproductively successful than homogenous ones. Through social heterosis, genetic diversity persists without: frequency dependence within groups, migration, balancing selection, genetic linkages, overdominance, antagonistic pleiotropy or nonrandom allele assortment. Social heterosis may also offer an alternative evolutionary pathway to cooperation that does not require clustering of related individuals, nepotistic favouritism towards kin, or overt reciprocity.
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Affiliation(s)
- P Nonacs
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA.
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36
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Arnegard ME, Jackson BS, Hopkins CD. Time-domain signal divergence and discrimination without receptor modification in sympatric morphs of electric fishes. J Exp Biol 2006; 209:2182-98. [PMID: 16709920 DOI: 10.1242/jeb.02239] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Polymorphism in an animal communication channel provides a framework for studying proximate rules of signal design as well as ultimate mechanisms of signal diversification. Reproductively isolated mormyrid fishes from Gabon's Brienomyrus species flock emit distinctive electric organ discharges(EODs) thought to function in species and sex recognition. Species boundaries and EODs appear congruent in these fishes, with the notable exception of three morphs designated types I, II and III. Within the species flock, these morphs compose a monophyletic group that has recently been called the magnostipes complex. Co-occurring morphs of this complex express distinctive EODs, yet they appear genetically indistinguishable at several nuclear loci. In this study, we investigated EOD discrimination by these morphs using both behavioral and physiological experiments. During the breeding season, wild-caught type I and type II males showed evidence that they can discriminate their own morph's EOD waveform from that of a sympatric and genetically distinct reference species. However, we found that type I and type II males exhibited an asymmetry in unconditioned responses to paired playback of EODs recorded from type I versus type II females. Males of the type II morph responded preferentially to EODs of type II females,whereas type I males did not appear to discriminate homotypic and heterotypic EODs in our experimental paradigm. Part of this behavioral asymmetry may have resulted from a previously undetected difference in adult size, which may have enhanced apparent discrimination by the smaller morph (type II) due to a relatively higher risk of injury from the larger morph (type I). Knollenorgan receptors, which mediate electrical communication in mormyrids, showed similar spectral tuning in type I and type II. These electroreceptors coded temporal features of any single magnostipes-complex EOD with similar patterns of time-locked spikes in both morphs. By contrast, Knollenorgans exhibited distinctive responses to different EOD waveforms. These results suggest that discrete EOD variation in this rapidly diversifying complex is functional in terms of morph-specific advertisement and recognition. Time-domain signal divergence has outpaced frequency-domain divergence between sympatric morphs,requiring little to no change in receptor response properties. We discuss our findings in light of a model for EOD time-coding by the Knollenorgan pathway,as well as evolutionary hypotheses concerning sympatric signal diversification in the magnostipes complex.
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Affiliation(s)
- Matthew E Arnegard
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
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Feulner PGD, Kirschbaum F, Schugardt C, Ketmaier V, Tiedemann R. Electrophysiological and molecular genetic evidence for sympatrically occuring cryptic species in African weakly electric fishes (Teleostei: Mormyridae: Campylomormyrus). Mol Phylogenet Evol 2006; 39:198-208. [PMID: 16271299 DOI: 10.1016/j.ympev.2005.09.008] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 09/07/2005] [Accepted: 09/07/2005] [Indexed: 11/23/2022]
Abstract
For two sympatric species of African weakly electric fish, Campylomormyrus tamandua and Campylomormyrus numenius, we monitored ontogenetic differentiation in electric organ discharge (EOD) and established a molecular phylogeny, based on 2222bp from cytochrome b, the S7 ribosomal protein gene, and four flanking regions of unlinked microsatellite loci. In C. tamandua, there is one common EOD type, regardless of age and sex, whereas in C. numenius we were able to identify three different male adult EOD waveform types, which emerged from a single common EOD observed in juveniles. Two of these EOD types formed well supported clades in our phylogenetic analysis. In an independent line of evidence, we were able to affirm the classification into three groups by microsatellite data. The correct assignment and the high pairwise F(ST) values support our hypothesis that these groups are reproductively isolated. We propose that in C. numenius there are cryptic species, hidden behind similar and, at least as juveniles, identical morphs.
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Affiliation(s)
- P G D Feulner
- Unit of Evolutionary Biology/Systematic Zoology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
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