Intragenus (Campylomormyrus) and intergenus hybrids in mormyrid fish: Physiological and histological investigations of the electric organ ontogeny

Kirschbaum, Frank; Nguyen, Linh P.; Baumgartner, Stephanie; Linda, Hiu Wan; Wolfart, Rene; Elarbani, Khouloud; Eppenstein, Hari; Korniienko, Yevheniia; Guido-Böhm, Lilian; Mamonékéné, Victor; Vater, Marianne; Tiedemann, Ralph

doi:10.1016/j.jphysparis.2017.01.003

Cited by 15 publications

(44 citation statements)

References 19 publications

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“…We note that the only other documented case of mormyrids with mixed‐morphology electrocytes was described in artificially created crosses between the biphasic mormyrid Campylomormyrus tshokwe and triphasic Campylomormyrus tamandua (Kirschbaum et al. 2016).…”

Section: Discussionmentioning

confidence: 84%

Genetic drift does not sufficiently explain patterns of electric signal variation among populations of the mormyrid electric fishParamormyrops kingsleyae

et al. 2020

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Communication signals serve crucial survival and reproductive functions. In Gabon, the widely distributed mormyrid fishParamormyrops 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. K E Y W O R D S : Animal communication, electric organ, electrocytes, genetic drift, signal evolution, weakly electric fish.

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Section: Discussionmentioning

confidence: 84%

Genetic drift does not sufficiently explain patterns of electric signal variation among populations of the mormyrid electric fishParamormyrops kingsleyae

et al. 2020

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“…A complementary approach could be a co-segregation analysis among EOD phenotypes and genetic variants among F2-species hybrids. Indeed, hybridization of our species is possible [ 74 ] and some F1 hybrids are fertile [ 75 ], but so far no F2 hybrids could be brought to a stage where they exhibit an adult EOD. Consequently, we can so far not proof a direct link between the inferred candidate genes and processes and the actual electric organ/electrocyte features.…”

Section: Discussionmentioning

confidence: 99%

Transcriptome-wide single nucleotide polymorphisms related to electric organ discharge differentiation among African weakly electric fish species

2020

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African weakly electric fish of the mormyrid genus Campylomormyrus generate pulse-type electric organ discharges (EODs) for orientation and communication. Their pulse durations are species-specific and elongated EODs are a derived trait. So far, differential gene expression among tissue-specific transcriptomes across species with different pulses and point mutations in single ion channel genes indicate a relation of pulse duration and electrocyte geometry/excitability. However, a comprehensive assessment of expressed Single Nucleotide Polymorphisms (SNPs) throughout the entire transcriptome of African weakly electric fish, with the potential to identify further genes influencing EOD duration, is still lacking. This is of particular value, as discharge duration is likely based on multiple cellular mechanisms and various genes. Here we provide the first transcriptome-wide SNP analysis of African weakly electric fish species (genus Campylomormyrus ) differing by EOD duration to identify candidate genes and cellular mechanisms potentially involved in the determination of an elongated discharge of C . tshokwe . Non-synonymous substitutions specific to C . tshokwe were found in 27 candidate genes with inferred positive selection among Campylomormyrus species. These candidate genes had mainly functions linked to transcriptional regulation, cell proliferation and cell differentiation. Further, by comparing gene annotations between C . compressirostris (ancestral short EOD) and C . tshokwe (derived elongated EOD), we identified 27 GO terms and 2 KEGG pathway categories for which C . tshokwe significantly more frequently exhibited a species-specific expressed substitution than C . compressirostris . The results indicate that transcriptional regulation as well cell proliferation and differentiation take part in the determination of elongated pulse durations in C . tshokwe . Those cellular processes are pivotal for tissue morphogenesis and might determine the shape of electric organs supporting the observed correlation between electrocyte geometry/tissue structure and discharge duration. The inferred expressed SNPs and their functional implications are a valuable resource for future investigations on EOD durations.

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“…Sympatric species often display asymmetric sexual isolation behaviours, with one species discriminating more strongly than vice versa 45 , 46 . However, an effort to obtain natural hybrids in breeding groups between female C. compressirostris and male C. tamandua led to several spawning events, but never fertilization 47 . This corresponds with previous research showing that C. tamandua males do preferentially associate with female conspecifics (over female C. compressirostris ) when live fish are used as stimuli 31 .…”

Section: Discussionmentioning

confidence: 99%

“…A recent genetic analysis also shows no evidence of gene flow between the two species, although incipient speciation is apparent 30 . Artificial reproduction between C. compressirostris and C. tamandua individuals produces fertile offspring and F1-hybrids produce viable fish 47 .…”

Section: Discussionmentioning

confidence: 99%

“…While the EOD waveform and SPI are both relevant for species recognition and discrimination in C. compressirostris , electric cues alone may not be sufficient for discrimination in C. tamandua . Molecular phylogenies of the Campylomormyrus genus show C. tamandua as the sister species of all other Campylomormyrus representatives 30 and morphological investigations into the electric organ suggest that the rostral position of the stalk found in C. tamandua is the ancestral state 47 , 48 . Discrimination by electric cues alone may, therefore, be an apomorphic trait evolved during a more recent radiation (i.e., after separation from C. tamandua ), while electric cues alone may not be sufficient for species recognition and discrimination in C. tamandua .…”

Section: Discussionmentioning

confidence: 99%

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Electric pulse characteristics can enable species recognition in African weakly electric fish species

Nagel

Kirschbaum

Hofmann

et al. 2018

Sci Rep

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Communication is key to a wide variety of animal behaviours and multiple modalities are often involved in this exchange of information from sender to receiver. The communication of African weakly electric fish, however, is thought to be predominantly unimodal and is mediated by their electric sense, in which species-specific electric organ discharges (EODs) are generated in a context-dependent and thus variable sequence of pulse intervals (SPI). While the primary function of the electric sense is considered to be electrolocation, both of its components likely carry information regarding identity of the sender. However, a clear understanding of their contribution to species recognition is incomplete. We therefore analysed these two electrocommunication components (EOD waveform and SPI statistics) in two sympatric mormyrid Campylomormyrus species. In a set of five playback conditions, we further investigated which components may drive interspecific recognition and discrimination. While we found that both electrocommunication components are species-specific, the cues necessary for species recognition differ between the two species studied. While the EOD waveform and SPI were both necessary and sufficient for species recognition in C. compressirostris males, C. tamandua males apparently utilize other, non-electric modalities. Mapped onto a recent phylogeny, our results suggest that discrimination by electric cues alone may be an apomorphic trait evolved during a recent radiation in this taxon.

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Intragenus (Campylomormyrus) and intergenus hybrids in mormyrid fish: Physiological and histological investigations of the electric organ ontogeny

Cited by 15 publications

References 19 publications

Genetic drift does not sufficiently explain patterns of electric signal variation among populations of the mormyrid electric fishParamormyrops kingsleyae

Genetic drift does not sufficiently explain patterns of electric signal variation among populations of the mormyrid electric fishParamormyrops kingsleyae

Transcriptome-wide single nucleotide polymorphisms related to electric organ discharge differentiation among African weakly electric fish species

Electric pulse characteristics can enable species recognition in African weakly electric fish species

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