Intergenus F1-hybrids of African weakly electric fish (Mormyridae: Gnathonemus petersii ♂ × Campylomormyrus compressirostris ♀) are fertile

Ralph Tiedemann,Yevheniia Korniienko,Frank Kirschbaum,Kingsley C. Nzimora,Marianne Vater

doi:10.1007/s00359-022-01542-5

Ralph Tiedemann, Yevheniia Korniienko + Show 3 more

Open Access

https://doi.org/10.1007/s00359-022-01542-5

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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.

Highlights

The African weakly electric mormyrids comprise more than 200 species in 21 genera (Alves-Gomes and Hopkins 1997; Ozouf-Costaz et al 2015; Sullivan and Lavoué 2015; NelsonThe 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, 2008, 2009b; Lamanna et al 2016; Kirschbaum et al 2016)
Species of this genus are characterised by very diverse electric organ discharge (EOD) that differ in shape and duration from ca. 200 μs to ca. 25 ms as in C. rhynchophorus and C. numenius (Feulner et al 2008, 2009a, 2009b; Nguyen et al 2020)
Hybrids between male G. petersii and female C. compressirostris were generated by artificial reproduction (AR), a technique already described for several mormyrid species (Nguyen et al 2017) and for intragenus (Campylomormyrus) (Kirschbaum et al 2016; Korniienko et al 2020) and intergenus hybridisations (Kirschbaum et al 2016)

Summary

Introduction

The African weakly electric mormyrids comprise more than 200 species in 21 genera (Alves-Gomes and Hopkins 1997; Ozouf-Costaz et al 2015; Sullivan and Lavoué 2015; NelsonThe 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, 2008, 2009b; Lamanna et al 2016; Kirschbaum et al 2016). In C. tamandua, the main stalk is located at the rostral face of the electrocyte and the small stalks penetrate the electrocyte from the caudal to the rostral face (Paul et al 2015) This feature correlates with the presence of an initial head negative phase in the EOD 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)

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