02556nas a2200277 4500008004100000022002500041245011800066210006900184260001600253300001000269490000800279520169400287653002801981653001302009653002002022653002602042653002602068653001302094100001702107700002102124700002302145700001902168700002102187700002202208856004802230 2016 eng d a0378-1909, 1573-513300aReproduction and development in some species of the weakly electric genus Campylomormyrus (Mormyridae, Teleostei)0 aReproduction and development in some species of the weakly elect cDec-07-2016 a49-680 v1003 a

Reproduction in captivity of four species of the mormyrid genus Campylomormyrus was investigated. Cyclical reproduction was provoked by changing water conductivity (C) alone: decreasing C led to gonadal recrudescence, an increase induced gonad regression. Data on the reproduction and development of three species are presented. All three species are indeterminate fractional spawners. Spawning intervals ranged from 6 to 66 days in C. rhynchophorus, 10–75 days in C. tshokwe, and 18 days in C. compressirostris (calculated values). Fecundities (eggs per fractional spawning) ranged from 70 to 1570 eggs in C. rhynchophorus, 100–1192 in C. tshokwe, and 38–246 in C. compressirostris. Spawnings/ovipositions occurred during the second half of the night; no parental care was observed; no special spawning substrates were necessary. C. compressirostris successfully spawned in breeding groups, C. rhynchophorus as pair. Agonistic behavior in the C. tshokwe pair forced us to divide the breeding tank; therefore, only ovipositions occurred. However, injection of an artificial GnRH hormone allowed us to obtain ripe eggs and sperm and to perform successful artificial reproduction. All three species produce yolky, slightly sticky eggs. Egg diameter ranges from 2.3–3.0 mm. Hatching occurred on day 3, feeding started on day 11. Transition from larval to juvenile stage occurred at around 20 mm total length (TL). At this size C. rhynchophorus developed a higher body than the two other species and differences between the species in the melanin pigmentation of the unpaired fins occurred. Between 32 and 35 mm TL the upper and lower jaws started to elongate.

10aArtificial reproduction10aBehavior10aCampylomormyrus10aCyclical reproduction10aEnvironmental factors10aOntogeny1 aNguyen, Linh1 aPaul, Christiane1 aMamonekene, Victor1 aBartsch, Peter1 aTiedemann, Ralph1 aKirschbaum, Frank uhttp://dx.doi.org/10.1007/s10641-016-0554-104135nas a2200193 4500008004100000022001400041245016700055210006900222260001600291490000700307520344900314100001603763700002203779700003003801700001803831700002203849700002103871856004903892 2023 eng d a1471-216400aA new genome assembly of an African weakly electric fish (Campylomormyrus compressirostris, Mormyridae) indicates rapid gene family evolution in Osteoglossomorpha0 anew genome assembly of an African weakly electric fish Campylomo cMar-20-20230 v243 a

Abstract Background Teleost fishes comprise more than half of the vertebrate species. Within teleosts, most phylogenies consider the split between Osteoglossomorpha and Euteleosteomorpha/Otomorpha as basal, preceded only by the derivation of the most primitive group of teleosts, the Elopomorpha. While Osteoglossomorpha are generally species poor, the taxon contains the African weakly electric fish (Mormyroidei), which have radiated into numerous species. Within the mormyrids, the genus Campylomormyrus is mostly endemic to the Congo Basin. Campylomormyrus serves as a model to understand mechanisms of adaptive radiation and ecological speciation, especially with regard to its highly diverse species-specific electric organ discharges (EOD). Currently, there are few well-annotated genomes available for electric fish in general and mormyrids in particular. Our study aims at producing a high-quality genome assembly and to use this to examine genome evolution in relation to other teleosts. This will facilitate further understanding of the evolution of the osteoglossomorpha fish in general and of electric fish in particular. Results A high-quality weakly electric fish (C. compressirostris) genome was produced from a single individual with a genome size of 862 Mb, consisting of 1,497 contigs with an N50 of 1,399 kb and a GC-content of 43.69%. Gene predictions identified 34,492 protein-coding genes, which is a higher number than in the two other available Osteoglossomorpha genomes of Paramormyrops kingsleyae and Scleropages formosus. A Computational Analysis of gene Family Evolution (CAFE5) comparing 33 teleost fish genomes suggests an overall faster gene family turnover rate in Osteoglossomorpha than in Otomorpha and Euteleosteomorpha. Moreover, the ratios of expanded/contracted gene family numbers in Osteoglossomorpha are significantly higher than in the other two taxa, except for species that had undergone an additional genome duplication (Cyprinus carpio and Oncorhynchus mykiss). As potassium channel proteins are hypothesized to play a key role in EOD diversity among species, we put a special focus on them, and manually curated 16 Kv1 genes. We identified a tandem duplication in the KCNA7a gene in the genome of C. compressirostris. Conclusions We present the fourth genome of an electric fish and the third well-annotated genome for Osteoglossomorpha, enabling us to compare gene family evolution among major teleost lineages. Osteoglossomorpha appear to exhibit rapid gene family evolution, with more gene family expansions than contractions. The curated Kv1 gene family showed seven gene clusters, which is more than in other analyzed fish genomes outside Osteoglossomorpha. The KCNA7a, encoding for a potassium channel central for EOD production and modulation, is tandemly duplicated which may related to the diverse EOD observed among Campylomormyrus species.

1 aCheng, Feng1 aDennis, Alice, B.1 aOsuoha, Josephine, Ijeoma1 aCanitz, Julia1 aKirschbaum, Frank1 aTiedemann, Ralph uhttp://dx.doi.org/10.1186/s12864-023-09196-603202nas a2200301 4500008004100000022001400041245015100055210006900206260000900275300001300284490000700297520224500304653001202549653001802561653001902579653001602598653002002614653003002634653003102664653001402695653003602709653002402745653001802769100001802787700002202805700002102827856005202848 2020 eng d a1932-620300aTranscriptome-wide single nucleotide polymorphisms related to electric organ discharge differentiation among African weakly electric fish species.0 aTranscriptomewide single nucleotide polymorphisms related to ele c2020 ae02408120 v153 a

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.

10aAnimals10aelectric fish10aelectric organ10aElectricity10aGene Expression10aGene Expression Profiling10aGene Expression Regulation10aPhenotype10aPolymorphism, Single Nucleotide10aSpecies Specificity10atranscriptome1 aCanitz, Julia1 aKirschbaum, Frank1 aTiedemann, Ralph uhttps://mormyrids.efishgenomics.com/en/node/62601616nas a2200169 4500008004100000022001400041245015000055210006900205260001600274520099000290100002601280700002501306700002001331700002101351700002201372856005201394 2022 eng d a1432-135100aIntergenus F1-hybrids of African weakly electric fish (Mormyridae: Gnathonemus petersii ♂ × Campylomormyrus compressirostris ♀) are fertile.0 aIntergenus F1hybrids of African weakly electric fish Mormyridae  c2022 Feb 043 a

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.

1 aKorniienko, Yevheniia1 aNzimora, Kingsley, C1 aVater, Marianne1 aTiedemann, Ralph1 aKirschbaum, Frank uhttps://mormyrids.efishgenomics.com/en/node/60802043nas a2200205 4500008004100000022001400041245014400055210006900199260001600268300001400284490000800298520134200306100002601648700001701674700002701691700002001718700002101738700002201759856005601781 2020 eng d a0340-759400aIntragenus F1-hybrids of African weakly electric fish (Mormyridae: Campylomormyrus tamandua ♂ × C. compressirostris ♀) are fertile0 aIntragenus F1hybrids of African weakly electric fish Mormyridae  cJan-07-2020 a571 - 5850 v2063 a

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 the F2-generation concerning the structure of the electric organ and features of the electric organ discharge. These F1-hybrids achieved sexual maturity at about 12–13.5 cm total length. A breeding group comprising six males and 13 females spawned 28 times naturally proving these F1-fish to be fertile. On average 228 eggs were spawned, the average fertilization rate was 47.8%. Eggs started to hatch 70–72 h after fertilization, average hatching rate was 95.6%. Average mortality rate during embryonic development amounted to 2.3%. Average malformation rate during the free embryonic stage was 27.7%. Exog- enous feeding started on day 11. In total, we raised 353 normally developed larvae all of which died consecutively, the oldest specimen reaching an age of 5 months. During survival, the activities of the larval and adult electric organs were recorded and the structure of the adult electric organ was investigated histologically.

1 aKorniienko, Yevheniia1 aNguyen, Linh1 aBaumgartner, Stephanie1 aVater, Marianne1 aTiedemann, Ralph1 aKirschbaum, Frank uhttp://link.springer.com/10.1007/s00359-020-01425-702385nas a2200157 4500008004100000022001400041245011300055210006900168260001600237520163800253100002601891700002101917700002001938700002201958856024701980 2020 eng d a0021-996700aOntogeny of the electric organ discharge and of the papillae of the electrocytes in the weakly electric fish0 aOntogeny of the electric organ discharge and of the papillae of  cDec-08-20203 a

The electric organ of the mormyrid weakly electric fish, Campylomormyrus rhynchophorus (Boulenger, 1898), undergoes changes in both the electric organ discharge (EOD) and the light and electron microscopic morphology as the fish mature from the juvenile to the adult form. Of particular interest was the appearance of papillae, surface specializations of the uninnervated anterior face of the electrocyte, which have been hypothesized to increase the duration of the EOD. In a 24.5 mm long juvenile the adult electric organ (EO) was not yet functional, and the electrocytes lacked papillae. A 40 mm long juvenile, which produced a short biphasic EOD of 1.3 ms duration, shows small papillae (average area 136 μm2). In contrast, the EOD of a 79 mm long juvenile was triphasic. The large increase in duration of the EOD to 23.2 ms was accompanied by a small change in size of the papillae (average area 159 μm2). Similarly, a 150 mm long adult produced a triphasic EOD of comparable duration to the younger stage (24.7 ms) but featured a prominent increase in size of the papillae (average area 402 μm2). Thus, there was no linear correlation between EOD duration and papillary size. The most prominent ultrastructural change was at the level of the myofilaments, which regularly extended into the papillae, only in the oldest specimen – probably serving a supporting function. Physiological mechanisms, like gene expression levels, as demonstrated in some Campylomormyrus species, might be more important concerning the duration of the EOD.

1 aKorniienko, Yevheniia1 aTiedemann, Ralph1 aVater, Marianne1 aKirschbaum, Frank uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/cne.25003https://onlinelibrary.wiley.com/doi/pdf/10.1002/cne.25003https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fcne.25003https://onlinelibrary.wiley.com/doi/pdf/10.1002/cne.2500301976nas a2200169 4500008004100000022001400041245012300055210006900178260001600247520138800263100001601651700001901667700002101686700002201707700002101729856005601750 2020 eng d a0269-765300aMorphological differentiation in African weakly electric fish (genus Campylomormyrus) relates to substrate preferences0 aMorphological differentiation in African weakly electric fish ge cApr-04-20213 a

Under an ecological speciation scenario, the radiation of African weakly electric fish (genus Campylomormyrus) is caused by an adaptation to different food sources, associated with diversification of the electric organ discharge (EOD). This study experimentally investigates a phenotype–environment correlation to further support this scenario. Our behavioural experiments showed that three sympatric Campylomormyrus species with significantly divergent snout morphology differentially react to variation in substrate structure. While the short snout species (C. tamandua) exhibits preference to sandy substrate, the long snout species (C. rhynchophorus) significantly prefers a stone substrate for feeding. A third species with intermediate snout size (C. compressirostris) does not exhibit any substrate preference. This preference is matched with the observation that long-snouted specimens probe deeper into the stone substrate, presumably enabling them to reach prey more distant to the substrate surface. These findings suggest that the diverse feeding apparatus in the genus Campylomormyrus may have evolved in adaptation to specific microhabitats, i.e., substrate structures where these fish forage. Whether the parallel divergence in EOD is functionally related to this adaptation or solely serves as a prezygotic isolation mechanism remains to be elucidated.

1 aAmen, Rahma1 aNagel, Rebecca1 aHedt, Maximilian1 aKirschbaum, Frank1 aTiedemann, Ralph uhttp://link.springer.com/10.1007/s10682-020-10043-3