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/s10682-020-10043-302093nas a2200169 4500008004100000245010600041210006900147260001600216490000600232520152800238100001901766700002201785700002001807700002101827700002101848856005401869 2018 eng d00aElectric pulse characteristics can enable species recognition in African weakly electric fish species0 aElectric pulse characteristics can enable species recognition in cJan-12-20180 v83 a

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.

1 aNagel, Rebecca1 aKirschbaum, Frank1 aHofmann, Volker1 aEngelmann, Jacob1 aTiedemann, Ralph uhttp://www.nature.com/articles/s41598-018-29132-z03057nas a2200313 4500008004100000022001300041245015100054210006900205260001600274520202800290653002802318653002002346653002802366653001202394653001402406100002202420700001702442700002702459700001502486700001802501700002302519700002102542700002602563700002402589700002302613700002002636700002102656856006602677 2017 eng d a0928425700aIntragenus (Campylomormyrus) and intergenus hybrids in mormyrid fish: physiological and histological investigations of the electric organ ontogeny0 aIntragenus Campylomormyrus and intergenus hybrids in mormyrid fi cJan-01-20173 a

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 42 days 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. Seven 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 x C. compressirostris are fertile: viable F2-fish could be obtained with artificial reproduction

10aArtificial reproduction10aCampylomormyrus10aElectric organ ontogeny10aHybrids10amormyrids1 aKirschbaum, Frank1 aNguyen, Linh1 aBaumgartner, Stephanie1 aChi, Linda1 aWolfart, Rene1 aElarbani, Khouloud1 aEppenstein, Hari1 aKorniienko, Yevheniia1 aGuido-Böhm, Lilian1 aMamonekene, Victor1 aVater, Marianne1 aTiedemann, Ralph uhttp://linkinghub.elsevier.com/retrieve/pii/S092842571730003702253nas a2200169 4500008004100000022001400041245012600055210006900181260001600250300001100266520166400277100002101941700002201962700002301984700002102007856005502028 2016 eng d a0022-284400aEvidence for Non-neutral Evolution in a Sodium Channel Gene in African Weakly Electric Fish (Campylomormyrus, Mormyridae)0 aEvidence for Nonneutral Evolution in a Sodium Channel Gene in Af cJan-08-2016 a1–173 a

Voltage-gated sodium channels, Nav1, play a crucial role in the generation and propagation of action potentials and substantially contribute to the shape of their rising phase. The electric organ discharge (EOD) of African weakly electric fish (Mormyroidea) is the sum of action potentials fired from all electrocytes of the electric organ at the same time and hence voltage-gated sodium channels are one factor—together with the electrocyte’s morphology and innervation pattern—that determines the properties of these EODs. Due to the fish-specific genome duplication, teleost fish possess eight copies of sodium channel genes (SCN), which encode for Nav1 channels. In mormyroids, SCN4aa is solely expressed in the electrocytes of the adult electric organ. In this study, we compared entire SCN4aa sequences of six species of the genus Campylomormyrus and identified nonsynonymous substitutions among them. SCN4aa in Campylomormyrus exhibits a much higher evolutionary rate compared to its paralog SCN4ab, whose expression is not restricted to the electric organ. We also found evidence for strong positive selection on the SCN4aa gene within Mormyridae and along the lineage ancestral to the Mormyridae. We have identified sites at which all nonelectric teleosts are monomorphic in their amino acid, but mormyrids have different amino acids. Our findings confirm the crucial role of SCN4aa in EOD evolution among mormyrid weakly electric fish. The inferred positive selection within Mormyridae makes this gene a prime candidate for further investigation of the divergent evolution of pulse-type EODs among closely related species.

1 aPaul, Christiane1 aKirschbaum, Frank1 aMamonekene, Victor1 aTiedemann, Ralph uhttp://link.springer.com/10.1007/s00239-016-9754-802056nas a2200265 4500008004100000022001300041245015000054210006900204260001600273520114000289653002001429653002801449653002001477653001501497653002801512653002501540100002301565700002201588700002201610700002701632700002301659700002101682700002101703856006601724 2016 eng d a1055790300aSpecies delimitation and phylogenetic relationships in a genus of African weakly-electric fishes (Osteoglossiformes, Mormyridae, Campylomormyrus)0 aSpecies delimitation and phylogenetic relationships in a genus o cJan-04-20163 a

African weakly-electric fishes (Mormyridae) are able to communicate through species-specific electric signals; this feature might have favoured the evolutionary radiation observed in this family (over 200 species) by acting as an effective pre-zygotic isolation mechanism. In the present study we used mitochondrial (cytb) and nuclear (rps7, scn4aa) markers in order to reconstruct a species-phylogeny and identify species boundaries for the genus Campylomormyrus, by applying inference methods based on the multispecies coalescent model. Additionally, we employed 16 microsatellite markers, landmark-based morphometric measurements, and electro-physiological analyses as independent lines of evidence to the results obtained from the sequence data. The results show that groups that are morphologically different are also significantly divergent at the genetic level, whereas morphologically similar groups, displaying dissimilar electric signals, do not show enough genetic diversity to be considered separate species. Furthermore, the data confirm the presence of a yet undescribed species within the genus Campylomormyrus.

10aCampylomormyrus10aGeometric morphometrics10aMicrosatellites10aMormyridae10aMultispecies-coalescent10aSpecies-delimitation1 aLamanna, Francesco1 aKirschbaum, Frank1 aErnst, Anja, R.R.1 aFeulner, Philine, G.D.1 aMamonekene, Victor1 aPaul, Christiane1 aTiedemann, Ralph uhttp://linkinghub.elsevier.com/retrieve/pii/S105579031630078102081nas a2200217 4500008004100000022001400041245012600055210006900181260001600250300001400266490000800280520136500288100002101653700002301674700002001697700002701717700002101744700002101765700002201786856005501808 2015 eng d a0340-759400aComparative histology of the adult electric organ among four species of the genus Campylomormyrus (Teleostei: Mormyridae)0 aComparative histology of the adult electric organ among four spe cJan-04-2015 a357 - 3740 v2013 a

The electric organ (EO) of weakly electric mormyrids consists of flat, disk-shaped electrocytes with distinct anterior and posterior faces. There are multiple species-characteristic patterns in the geometry of the electrocytes and their innervation. To further correlate electric organ discharge (EOD) with EO anatomy, we examined four species of the mormyrid genus Campylomormyrus possessing clearly distinct EODs. In C. compressirostris, C. numenius, and C. tshokwe, all of which display biphasic EODs, the posterior face of the electrocytes forms evaginations merging to a stalk system receiving the innervation. In C. tamandua that emits a triphasic EOD, the small stalks of the electrocyte penetrate the electrocyte anteriorly before merging on the anterior side to receive the innervation. Additional differences in electrocyte anatomy among the former three species with the same EO geometry could be associated with further characteristics of their EODs. Furthermore, in C. numenius, ontogenetic changes in EO anatomy correlate with profound changes in the EOD. In the juvenile the anterior face of the electrocyte is smooth, whereas in the adult it exhibits pronounced surface foldings. This anatomical difference, together with disparities in the degree of stalk furcation, probably contributes to the about 12 times longer EOD in the adult.

1 aPaul, Christiane1 aMamonekene, Victor1 aVater, Marianne1 aFeulner, Philine, G.D.1 aEngelmann, Jacob1 aTiedemann, Ralph1 aKirschbaum, Frank uhttp://link.springer.com/10.1007/s00359-015-0995-603057nas a2200169 4500008004100000245015700041210006900198260001600267490000700283520243400290100002302724700002202747700002202769700002502791700002102816856005002837 2015 eng d00aCross-tissue and cross-species analysis of gene expression in skeletal muscle and electric organ of African weakly-electric fish (Teleostei; Mormyridae)0 aCrosstissue and crossspecies analysis of gene expression in skel cJan-12-20150 v163 a

Background: African weakly-electric fishes of the family Mormyridae are able to produce and perceive weak electric signals (typically less than one volt in amplitude) owing to the presence of a specialized, muscle-derived electric organ (EO) in their tail region. Such electric signals, also known as Electric Organ Discharges (EODs), are used for objects/prey localization, for the identification of conspecifics, and in social and reproductive behaviour. This feature might have promoted the adaptive radiation of this family by acting as an effective pre-zygotic isolation mechanism. Despite the physiological and evolutionary importance of this trait, the investigation of the genetic basis of its function and modification has so far remained limited. In this study, we aim at: i) identifying constitutive differences in terms of gene expression between electric organ and skeletal muscle (SM) in two mormyrid species of the genus Campylomormyrus: C. compressirostris and C. tshokwe, and ii) exploring cross-specific patterns of gene expression within the two tissues among C. compressirostris, C. tshokwe, and the outgroup species Gnathonemus petersii.
Results: Twelve paired-end (100 bp) strand-specific RNA-seq Illumina libraries were sequenced, producing circa 330 M quality-filtered short read pairs. The obtained reads were assembled de novo into four reference transcriptomes. In silico cross-tissue DE-analysis allowed us to identify 271 shared differentially expressed genes between EO and SM in C. compressirostris and C.tshokwe. Many of these genes correspond to myogenic factors, ion channels and pumps, and genes involved in several metabolic pathways. Cross-species analysis has revealed that the electric organ transcriptome is more variable in terms of gene expression levels across species than the skeletal muscle transcriptome.
Conclusions: The data obtained indicate that: i) the loss of contractile activity and the decoupling of the excitation-contraction processes are reflected by the down-regulation of the corresponding genes in the electric organ’s transcriptome; ii) the metabolic activity of the EO might be specialized towards the production and turn-over of membrane structures; iii) several ion channels are highly expressed in the EO in order to increase excitability; iv) several myogenic factors might be down-regulated by transcription repressors in the EO.

1 aLamanna, Francesco1 aKirschbaum, Frank1 aWaurick, Isabelle1 aDieterich, Christoph1 aTiedemann, Ralph uhttp://www.biomedcentral.com/1471-2164/16/66802535nas a2200157 4500008004100000245023400041210006900275260001600344300001600360490000700376520183100383100002302214700002202237700002102259856009702280 2014 eng d00aDe novo assembly and characterization of the skeletal muscle and electric organ transcriptomes of the African weakly electric fish Campylomormyrus compressirostris (Mormyridae, Teleostei)0 aiDe novoi assembly and characterization of the skeletal muscle a cJan-11-2014 a1222 - 12300 v143 a

African weakly electric fishes (Mormyridae) underwent an outstanding adaptive radiation (about 200 species), puta-tively owing to their ability to communicate through species-specific weak electric signals. The electric organdischarge (EOD) is produced by muscle-derived electrocytes organized in piles to form an electric organ. Despite theimportance of this trait as a prezygotic isolation mechanism, genomic resources remained limited. We present here afirst draft of the skeletal muscle and electric organ transcriptomes from the weakly electric fish species Camp-ylomormyrus compressirostris, obtained using the Illumina HiSeq2000 sequencing technology. Approximately 6.8Gbp of cDNA sequence data were produced from both tissues, resulting in 57 268 109 raw reads for the skeletal mus-cle and 46 934 923 for the electric organ, and assembled de novo into 46 143 and 89 270 contigs, respectively. About50% of both transcriptomes were annotated after protein databases search. The two transcriptomes show similarprofiles in terms of Gene Ontology categories composition. We identified several candidate genes which are likely toplay a central role in the production and evolution of the electric signal. For most of these genes, and for many otherhousekeeping genes, we were able to obtain the complete or partial coding DNA sequences (CDS), which can beused for the development of primers to be utilized in qRT-PCR experiments. We present also the complete mitochon-drial genome and compare it to those available from other weakly electric fish species. Additionally, we located 1671SSR-containing regions with their flanking sites and designed the relative primers. This study establishes a first stepin the development of genomic tools aimed at understanding the role of electric communication during speciation

1 aLamanna, Francesco1 aKirschbaum, Frank1 aTiedemann, Ralph uhttp://doi.wiley.com/10.1111/men.2014.14.issue-6http://doi.wiley.com/10.1111/1755-0998.12260