@article {668, title = {Length-weight relationships and condition factors of Mormyridae species in the Niger River: implications for conservation and management}, journal = {Limnology and Freshwater Biology }, volume = {2025}, year = {2025}, month = {Jan-01-2025}, pages = {215-221}, abstract = {

The length-weight relationship and condition factor of the ten most abundant Mormyridae species in the Niger River at Niamey were examined from August to November 2023. The species assessed were\ Mormyrus rume,\ Campylomormyrus tamandua,\ Pollimyrus isidori,\ Brienomyrus niger,\ Hyperopisus bebe, Mormyrus macrophthalmus,\ Mormyrops anguilloides,\ Brevimyrus niger,\ Mormyrops oudoti,\ Cyphomyrus Psittacus, and\ Marcusenius cyprinoides. Analysis of their length-weight relationships revealed \“b\” values ranging from 2.08 to 2.87, suggesting negative allometric growth across all species. Condition factor (k) values varied from 1.22 \± 0.31 for\ H. bebe\ to 10.48 \± 2.83 for\ M. cyprinoides, with no significant differences in average condition factors among the species. These findings highlight the potential vulnerability of Mormyridae species to environmental changes and anthropogenic pressures, emphasizing the need for targeted conservation measures. The results underscore the importance of sustainable fisheries management practices to preserve biodiversity and ensure the long-term productivity of the Niger River ecosystem. The observed negative allometric growth patterns indicate that environmental conditions may be suboptimal for these species, potentially due to factors such as habitat degradation, water quality issues, or overfishing. Addressing these challenges through habitat restoration and regulatory measures could enhance the resilience of fish populations and support sustainable fisheries.

}, keywords = {condition factor, length-weight analysis, Mormyridae, sustainable fisheries management, the Niger River}, issn = {2658-3518}, doi = {10.31951/2658-3518-2025-a-2-215}, url = {https://doi.org/10.31951/2658-3518-2025-a-2-215}, author = {Souley, S.M.N. and Harouna, M. and Ado, M.I. and Youssoufa, I.} } @article {667, title = {Organization of the stalk system on electrocytes in mormyrid weakly electric fish Campylomormyrus compressirostris}, journal = {Cell and Tissue Research}, year = {2024}, month = {Dec-20-2024}, pages = {1-17}, abstract = {

The adult electric organ in weakly electric mormyrid fish consists of action-potential-generating electrocytes, structurally and functionally modified skeletal muscle cells. The electrocytes have a disc-shaped portion and, on one of its sides, numerous thin processes, termed stalklets. These unite to stalks leading to a single main stalk that carries the innervation site. Here, we describe the 3-dimensional layout of the stalklet/stalk system in adult Campylomormyrus compressirostris by differential interference contrast microscopy and confocal fluorescence microscopy. Using antibodies against Na+/K+-ATPase \α-subunit and plasma membrane Ca2+-ATPase, we show that these ion pumps are differentially distributed over the stalklet/stalk system, with plasma membrane Ca2+-ATPase being enriched on the stalklet membrane. Stalklets are distributed and organized in a quite uniform pattern on the posterior face of the electrocyte disc and fuse to terminal stalks. The latter then unite in a mostly dichotomic mode to stalks of increasing thickness, with the main stalk measuring about 100\ \µm in diameter. We further analyse the structural organization of stalklets and stalks, with a characteristic cytoskeletal system of bundled actin filaments in the centre and nuclei in subsurface position. These results suggest that the stalklet/stalk system is adapted in its structural layout to generate an action potential highly synchronized over the entire disc-portion of the electrocyte, accounting for the short electric organ discharge in this species. Our results suggest that actin-related proteins overexpressed in electrocytes, as shown previously by transcriptome analysis, may be involved in the organization of the unique F-actin system in stalklets and stalks.

}, keywords = {Ca2+-ATPase, Confocal microscopy, electrocyte, F-actin, Plasma membrane, Sodium pump}, issn = {0302-766X, 1432-0878}, doi = {10.1007/s00441-024-03938-y}, url = {https://doi.org/10.1007/s00441-024-03938-y}, author = {Baumann, Otto and Cheng, Feng and Kirschbaum, Frank and Tiedemann, Ralph} } @article {660, title = {Diet of some fish species of the family Mormyridae (Actinopterygii: Teleostei; Bonaparte, 1831) from the upper Sanaga River, Central Region of Cameroon}, journal = {Journal of Animal Diversity}, volume = {6}, year = {2024}, month = {31 March 2024}, pages = {51-62}, chapter = {51}, abstract = {

This study was carried out between October 2020 and October 2021 with the aim of determining sustainable management options and nutrition for the domestication of Mormyridae fish species living in the Sanaga River in central Cameroon. For this purpose, 451 specimens collected from local fishermen were identified and grouped into four genera and seven species, constituting 20.84\% Campylomormyrus phantasticus (Pellegrin), 5.32\% Hippopotamyrus castor (Pappenheim), 24.61\% Mormyrops anguilloides (Linnaeus), 18.63\% Mormyrops caballus (Pellegrin), 4.66\% Mormyrops zanclirostris (G\ünther, 1867), 15.52\% Mormyrus rume (Valenciennes), and 10.42\% Mormyrus tapirus (Pappenheim). Fish were measured, and parameters were obtained after dissection using intestinal morphometric characteristics and stomach content analysis methods. The emptiness coefficient varied from 0\% (Hippopotamyrus castor and Mormyrops zanclirostris) to 26.66\% (Mormyrus rume). The relative mass of the intestine was low in all studied species; the intestinal coefficient and the Zihler index of all these species are within the range of carnivorous species. Analysis of stomach contents revealed a broad food spectrum containing twelve categories of prey. Insects, macrophytes and larval insect shelters were the preferred foods of Mormyrops anguilloides, Mormyrops caballus and Mormyrops zanclirostris, while insect larvae and larval shelters were the preferred prey for other species. Site and season had little effect on the categories of prey consumed by these species.

}, keywords = {Biodiversity, Ebebda, feeding, Monatele, Mormyridae, stomach contents}, doi = {10.22034/JAD.2024.6.1.5}, url = {http://dx.doi.org/10.22034/JAD.2024.6.1.5}, author = {Akohogni, MAM and Medjo, KE and Zebaze, TB and Chiassa, NKA and Mepa, TCP and Tiogu{\'e}, TC and Fon, ED} } @article {645, title = {Reproduction and development in some species of the weakly electric genus Campylomormyrus (Mormyridae, Teleostei)}, journal = {Environmental Biology of Fishes}, volume = {100}, year = {2016}, month = {Dec-07-2016}, pages = {49-68}, chapter = {49}, abstract = {

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.

}, keywords = {Artificial reproduction, Behavior, Campylomormyrus, Cyclical reproduction, Environmental factors, Ontogeny}, issn = {0378-1909, 1573-5133}, doi = {10.1007/s10641-016-0554-1}, url = {http://dx.doi.org/10.1007/s10641-016-0554-1}, author = {Nguyen, Linh and Paul, Christiane and Victor Mamonekene and Bartsch, Peter and Ralph Tiedemann and Kirschbaum, Frank} } @article {644, title = {Trophic ecology of the African riverine elephant fishes (Mormyridae)}, volume = {14}, year = {2024}, month = {Aug-01-2024}, abstract = {

Multiple species of the elephant fishes (Mormyridae) commonly coexist in sympatry in most African tropical rivers and lakes. In this study, we investigated the trophic ecology and potential trophic niche partitioning of eleven mormyrid fish species from the Sanaga River system in Cameroon using the stable isotope composition of carbon and nitrogen in the muscle samples. Albeit most mormyrids mainly feed on invertebrates, we found differences in isotope ratios, and we report signs of the trophic niche partitioning among species. We further found significant differences in isotopic signatures within the Mormyrus genus, suggesting ecological niche diversification among three closely related species. We have also evaluated differences in the isotopic signals between seasons in four species, which could be possibly caused by species migration and/or anthropogenic agricultural activities. To evaluate body shape, we applied geometric morphometric analyses, and we show that most of the species are clearly morphologically separated. We focused on the mormyrid ecomorphology to identify a possible interaction between shape and ecology, and we found a relationship between the \δ13C (but not \δ15N) isotopic signal and morphology, suggesting their interplay during mormyrid evolution. Overall, we present robust evidence of the trophic niche partitioning within the mormyrid species community, and we integrate trophic ecology with morphometrics, shedding light on the enigmatic evolutionary history of these fascinating African fishes.

}, keywords = {mormyrids, stable isotopes, trophic ecology, trophic position, trophic resource portioning}, issn = {2045-7758, 2045-7758}, doi = {10.1002/ece3.70173}, url = {http://dx.doi.org/10.1002/ece3.70173}, author = {Sommer, Gina Maria and Njom, Samuel Didier and Indermaur, Adrian and Nyom, Arnold Roger Bitja and Jandov{\'a}, Kate{\v r}ina and Kukla, Jaroslav and Petrt{\'y}l, Miloslav and Hork{\'a}, Petra and Musilova, Zuzana} } @article {640, title = {A new type of spermiogenesis in teleost fish: formation of the aflagellate sperm in Campylomormyrus compressirostris (Osteoglossomorpha: Mormyridae)}, journal = {Zoology}, year = {2024}, month = {29 June 2024}, abstract = {

Osteoglossomorpha, the bony tongue fishes, show great variation in morphology, behavioural strategies, reproductive biology and gamete ultrastructure. The order Osteoglossiformes is the only vertebrate taxon, in which four types of sperm (monoflagellate, biflagellate and aflagellate aquasperm and the complex introsperm) have been described. It is also the only vertebrate lineage in which aflagellate spermatozoa exist. The aim of this study was to analyse the structure of the testis and the process of spermiogenesis in the mormyrid Campylomormyrus compressirostris during the breeding season using light and electron microscopy (transmission and scanning). Males of this species have a single testis of the anastomosing tubular type. The tubules of the anterior part of the testis contain cysts with developing germ cells, and this region is much wider than the posterior part, which consists of efferent ducts filled with sperm cells. The cysts are filled with single or mitotic spermatogonia, primary and secondary spermatocytes and early spermatids. At the stage of spermatids with fine granular chromatin, the cysts rupture and successive stages of spermatid differentiation take place in the testicular lumen; we therefore characterise this process as \‘extracystic spermiogenesis\’. Sperm development in C. compressirostris is extremely simple and involves chromatin condensation in the central region of the nucleus, a slight decrease in nuclear volume, the appearance of numerous vesicles in the cytoplasm that form a tubular-vesicular system at the base of the nucleus. Both centrioles and mitochondria are translocated to the peripheral region of the midpiece, which forms the opposite pole to the nucleus. There are many differences between the types of spermiogenesis described so far in teleosts and that found in C. compressirostris, including the loss of flagellum formation. This unique type of spermiogenesis is restricted to species of the families Mormyridae and Gymnarchidae, all of which possess aflagellate spermatozoa. Our data demonstrate that the spermatid differentiation and existence of the aflagellate spermatozoon are a unique phenomena not only among teleosts but also in the whole vertebrate lineage.

}, keywords = {elephantfish, permatozoon, Sertoli cells, spermatids, Tubular testis}, doi = {10.1016/j.zool.2024.126186}, url = {https://www.sciencedirect.com/science/article/pii/S094420062400045X}, author = {Dymek, Anna M and Kirschbaum, Frank and Ralph Tiedemann and Siemi{\'n}ski, Krzysztof and Pecio, Anna} } @article {634, title = {Diet in phenotypically divergent sympatric species of African weakly electric fish (genus: Campylomormyrus){\textemdash}A hybrid capture/HTS metabarcoding approach}, year = {2023}, month = {Dec-21-2023}, abstract = {

Ecological speciation within the mormyrid genus Campylomormyrus resulted in sympatric species exhibiting divergence in their feeding apparatus and electric organ discharge (EOD). This study documents the overall diet of the genus Campylomormyrus and examines the hypothesis that the Campylomormyrus radiation is caused by adaptation to different food sources. We performed diet assessment of five sympatric Campylomormyrus species (C. alces, C. compressirostris, C. curvirostris, C. tshokwe, C. numenius) and their sister taxon Gnathonemus petersii with markedly different snout morphologies and EODs using hybrid capture/HTS DNA metabarcoding of their stomach contents. Our approach allowed for high taxonomic resolution of prey items, including benthic invertebrates, allochthonous invertebrates and vegetation. Comparisons of the diet compositions using quantitative measures and diet overlap indices revealed that all species are able to exploit multiple food niches in their habitats, that is fauna at the bottom, the water surface and the water column. A major part of the diet is larvae of aquatic insects, such as dipterans, coleopterans and trichopterans, known to occur in holes and interstitial spaces of the substrate. The results indicate that different snout morphologies and the associated divergence in the EOD could translate into different prey spectra. This suggests that the diversification in EOD and/or morphology of the feeding apparatus could be under functional adaptation.

}, issn = {0962-1083, 1365-294X}, doi = {10.1111/mec.17248}, url = {http://dx.doi.org/10.1111/mec.17248}, author = {Amen, Rahma and Havenstein, Katja and Kirschbaum, Frank and Ralph Tiedemann} } @inbook {633, title = {Exploration du Parc National de l{\textquoteright}Upemba Mission G.F. De Witte, Fascicule 73 Poissons}, booktitle = {Exploration du Parc National de l{\textquoteright}Upemba Mission G.F. De Witte}, volume = {73}, year = {1976}, publisher = {Fondation Pour Favoriser Les Recherches Scientifiques en Afrique}, organization = {Fondation Pour Favoriser Les Recherches Scientifiques en Afrique}, address = {Brussels}, author = {Poll, M.} } @article {630, title = {A new genome assembly of an African weakly electric fish (Campylomormyrus compressirostris, Mormyridae) indicates rapid gene family evolution in Osteoglossomorpha}, volume = {24}, year = {2023}, month = {Mar-20-2023}, abstract = {

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.

}, issn = {1471-2164}, doi = {10.1186/s12864-023-09196-6}, url = {http://dx.doi.org/10.1186/s12864-023-09196-6}, author = {Cheng, Feng and Dennis, Alice B. and Osuoha, Josephine Ijeoma and Canitz, Julia and Kirschbaum, Frank and Ralph Tiedemann} } @article {629, title = {Histology of Convergent Probing Appendages in Mormyridae}, journal = {Integrative Organismal Biology}, volume = {5}, year = {2023}, month = {Jan-01-2023}, abstract = {

Mormyridae is an early diverging family of Teleostean fishes that produce an electric field for navigation and communication using an electric organ. This clade has a diverse array of soft-tissue rostral appendages, such as the chin-swelling, the Schnauzenorgan, and the tubesnout combined with a Schnauzenorgan, that have evolved multiple times. Here we assess if macroscopically convergent, soft-tissue rostral appendages are also histologically convergent. Further, we investigate how the histology of these appendages can inform their function. We sampled independent gains of the chin-swelling and Schnauzenorgan to understand similarities and differences in their anatomies. We show that macroscopically convergent rostral appendages are also convergent at a histological level, and different types of rostral appendages share a similar anatomy; that said, minor differences likely relate to their specific functions. Based on a comparison of the skeletal muscle distribution and the differing attachment shapes of each appendage to the dentary, we conclude that the Schnauzenorgan is capable of a wider range of movements than the chin swelling. Furthermore, the anatomy suggests that these soft-tissue rostral appendages likely function as electrosensory foveas (i.e., an appendage that focuses a sensory system). Lastly, these histological data support the hypothesis that the chin swelling may be a precursor to the Schnauzenorgan.

}, issn = {2517-4843}, doi = {10.1093/iob/obad001}, url = {http://dx.doi.org/10.1093/iob/obad001}, author = {Rose Peterson and Evans, A J and Hernandez, L P} } @mastersthesis {625, title = {Genome and karyotype evolution underlying speciation and diversification of electric organ discharges in African weakly electric fish (Campylomormyrus, Mormyridae, Teleostei)}, volume = {PhD}, year = {2019}, month = {22 May 2019}, pages = {112}, school = {University of Potsdam}, type = {doctoral dissertation}, address = {Potsdam}, url = {https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/year/2020/docId/44305}, author = {Canitz, Julia} } @article {620, title = {The Complete Genome Sequences of 38 Species of Elephantfishes (Mormyridae, Osteoglossiformes)}, year = {2022}, month = {Nov-21-2022}, abstract = {

We present the complete genome sequences of 38 species of elephantfishes from 20 genera. Illumina sequencing was performed on genetic material from single wild-caught individuals. The reads were assembled using a de novo method followed by a finishing step. The raw and assembled data is publicly available via Genbank.

}, issn = {2687-7945}, doi = {10.56179/001c.56077}, url = {http://dx.doi.org/10.56179/001c.56077}, author = {Rose Peterson and John P Sullivan and Stacy Pirro} } @article {608, title = {Intergenus F1-hybrids of African weakly electric fish (Mormyridae: Gnathonemus petersii ♂ {\texttimes} Campylomormyrus compressirostris ♀) are fertile.}, journal = {J Comp Physiol A Neuroethol Sens Neural Behav Physiol}, year = {2022}, month = {2022 Feb 04}, 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.

}, issn = {1432-1351}, doi = {10.1007/s00359-022-01542-5}, author = {Korniienko, Yevheniia and Nzimora, Kingsley C and Vater, Marianne and Ralph Tiedemann and Kirschbaum, Frank} } @article {602, title = {Intragenus F1-hybrids of African weakly electric fish (Mormyridae: Campylomormyrus tamandua ♂ {\texttimes} C. compressirostris ♀) are fertile}, journal = {Journal of Comparative Physiology A}, volume = {206}, year = {2020}, month = {Jan-07-2020}, pages = {571 - 585}, abstract = {

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.

}, issn = {0340-7594}, doi = {10.1007/s00359-020-01425-7}, url = {http://link.springer.com/10.1007/s00359-020-01425-7}, author = {Korniienko, Yevheniia and Nguyen, Linh and Baumgartner, Stephanie and Vater, Marianne and Ralph Tiedemann and Kirschbaum, Frank} } @article {587, title = {Morphological differentiation in African weakly electric fish (genus Campylomormyrus) relates to substrate preferences}, journal = {Evolutionary Ecology}, year = {2020}, month = {Apr-04-2021}, abstract = {

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.

}, issn = {0269-7653}, doi = {10.1007/s10682-020-10043-3}, url = {http://link.springer.com/10.1007/s10682-020-10043-3}, author = {Amen, Rahma and Nagel, Rebecca and Hedt, Maximilian and Kirschbaum, Frank and Ralph Tiedemann} } @article {559, title = {Electric pulse characteristics can enable species recognition in African weakly electric fish species}, journal = {Scientific Reports}, volume = {8}, year = {2018}, month = {Jan-12-2018}, abstract = {

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.

}, doi = {10.1038/s41598-018-29132-z}, url = {http://www.nature.com/articles/s41598-018-29132-z}, author = {Nagel, Rebecca and Frank Kirschbaum and Hofmann, Volker and Engelmann, Jacob and Ralph Tiedemann} } @article {543, title = {Intragenus (Campylomormyrus) and intergenus hybrids in mormyrid fish: physiological and histological investigations of the electric organ ontogeny}, journal = {Journal of Physiology-Paris}, year = {2017}, month = {Jan-01-2017}, abstract = {

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

}, keywords = {Artificial reproduction, Campylomormyrus, Electric organ ontogeny, Hybrids, mormyrids}, issn = {09284257}, doi = {10.1016/j.jphysparis.2017.01.003}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0928425717300037}, author = {Frank Kirschbaum and Nguyen, Linh and Baumgartner, Stephanie and Chi, Linda and Wolfart, Rene and Elarbani, Khouloud and Eppenstein, Hari and Korniienko, Yevheniia and Guido-B{\"o}hm, Lilian and Victor Mamonekene and Vater, Marianne and Ralph Tiedemann} } @article {536, title = {Evidence for Non-neutral Evolution in a Sodium Channel Gene in African Weakly Electric Fish (Campylomormyrus, Mormyridae)}, journal = {Journal of Molecular Evolution}, year = {2016}, month = {Jan-08-2016}, pages = {1{\textendash}17}, abstract = {

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.

}, issn = {0022-2844}, doi = {10.1007/s00239-016-9754-8}, url = {http://link.springer.com/10.1007/s00239-016-9754-8}, author = {Paul, Christiane and Frank Kirschbaum and Victor Mamonekene and Ralph Tiedemann} } @article {499, title = {Species delimitation and phylogenetic relationships in a genus of African weakly-electric fishes (Osteoglossiformes, Mormyridae, Campylomormyrus)}, journal = {Molecular Phylogenetics and Evolution}, year = {2016}, month = {Jan-04-2016}, abstract = {

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.

}, keywords = {Campylomormyrus, Geometric morphometrics, Microsatellites, Mormyridae, Multispecies-coalescent, Species-delimitation}, issn = {10557903}, doi = {10.1016/j.ympev.2016.04.035}, url = {http://linkinghub.elsevier.com/retrieve/pii/S1055790316300781}, author = {Lamanna, Francesco and Frank Kirschbaum and Ernst, Anja R.R. and Philine G.D. Feulner and Victor Mamonekene and Paul, Christiane and Ralph Tiedemann} } @article {480, title = {Comparative histology of the adult electric organ among four species of the genus Campylomormyrus (Teleostei: Mormyridae)}, journal = {Journal of Comparative Physiology A}, volume = {201}, year = {2015}, month = {Jan-04-2015}, pages = {357 - 374}, abstract = {

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.

}, issn = {0340-7594}, doi = {10.1007/s00359-015-0995-6}, url = {http://link.springer.com/10.1007/s00359-015-0995-6}, author = {Paul, Christiane and Victor Mamonekene and Vater, Marianne and Philine G.D. Feulner and Engelmann, Jacob and Ralph Tiedemann and Frank Kirschbaum} } @article {478, title = {Cross-tissue and cross-species analysis of gene expression in skeletal muscle and electric organ of African weakly-electric fish (Teleostei; Mormyridae)}, journal = {BMC Genomics}, volume = {16}, year = {2015}, month = {Jan-12-2015}, abstract = {

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.

}, doi = {10.1186/s12864-015-1858-9}, url = {http://www.biomedcentral.com/1471-2164/16/668}, author = {Lamanna, Francesco and Frank Kirschbaum and Waurick, Isabelle and Dieterich, Christoph and Ralph Tiedemann} } @article {453, title = {De novo assembly and characterization of the skeletal muscle and electric organ transcriptomes of the African weakly electric fish Campylomormyrus compressirostris (Mormyridae, Teleostei)}, journal = {Molecular Ecology Resources}, volume = {14}, year = {2014}, month = {Jan-11-2014}, pages = {1222 - 1230}, abstract = {

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

}, doi = {10.1111/men.2014.14.issue-610.1111/1755-0998.12260}, url = {http://doi.wiley.com/10.1111/men.2014.14.issue-6http://doi.wiley.com/10.1111/1755-0998.12260}, author = {Lamanna, Francesco and Frank Kirschbaum and Ralph Tiedemann} }