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Breeding experiment with 19 F1-hybrids (6 males, 13 females) (C. tamandua ♂ × C. compressirostris ♀) for a period of 360 days. Red arrows indicate natural spawnings. Oviposited eggs were always fertilized (see Table 1). Triangle indicates successful artificial reproduction (see Kirschbaum et al. 2016). On day 260 the three biggest males were taken out of the breeding tank and were returned on day 337 (grey arrows). Note the stop and start of spawning activity
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Hybridization is widespread in fish and constitutes an important mechanism in fish speciation. There is, however, little knowledge about hybridization in mormyrids. F1-interspecies hybrids between Campylomormyrus tamandua ♂ × C. compressirostris ♀ were investigated concerning: (1) fertility; (2) survival of F2-fish and (3) new gene combinations in...
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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 ♂ × Campylomorm...
Urethane and MS-222 are agents widely employed for general anesthesia, yet, besides inducing a state of unconsciousness, little is known about their neurophysiological effects. To investigate these effects, we developed an in vivo assay using the electric organ discharge (EOD) of the weakly electric fish Apteronotus leptorhynchus as a proxy for the...
To understand animal ecology, observation of wildlife in the natural habitat is essential, but particularly challenging in the underwater realm. Weakly electric fishes provide an excellent opportunity to overcome some of these challenges because they generate electric organ discharges (EODs) to sense their environment and to communicate, which can...
Citations
... The mormyrid genus Campylomormyrus encompasses 15 species (Taverne 1972;Feulner et al. 2007), most of which are endemic to the Congo River basin (Feulner et al. 2007(Feulner et al. , 2008(Feulner et al. , 2009bLamanna et al. 2016;Kirschbaum et al. 2016). Species of this genus are characterised by very diverse EODs that differ in shape and duration from ca. 200 µs (as in C. compressirostris) to ca. 25 ms as in C. rhynchophorus and C. numenius (Feulner et al. 2008(Feulner et al. , 2009a(Feulner et al. , 2009bNguyen et al. 2020). In addition, there are basic differences in the anatomy of the electrocytes of the EO concerning the organisation and location of the stalk system, which consists of numerous small specialised protrusions of the electrocyte that fuse to form the main stalk, which receives the innervation by electromotor neurons. ...
... This feature correlates with the presence of an initial head negative phase in the EOD (Bass 1986;Gallant et al. 2011). In contrast, in the four species C. compressirostris, C. tshokwe, C. numenius and C. rhynchophorus there is no initial head negative phase in the EOD; the main stalk is found on the caudal face of the electrocyte and penetrations are absent (Paul et al. 2015;Nguyen et al. 2020). ...
... The aim of the current study, therefore, is a detailed description of the ontogeny of the EO and, in addition, to unravel whether these intergenus hybrids are fertile, as has been observed in intragenus Campylomormyrus (C. tamandua × C. compressirostris) hybrids (Kirschbaum et al. 2016;Korniienko et al. 2020). ...
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.
... 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. ...
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.
