TY - JOUR A1 - Paul, Christiane A1 - Mamonekene, Victor A1 - Vater, Marianne A1 - Feulner, Philine G. D. A1 - Engelmann, Jacob A1 - Tiedemann, Ralph A1 - Kirschbaum, Frank T1 - Comparative histology of the adult electric organ among four species of the genus Campylomormyrus (Teleostei: Mormyridae) JF - Journal of comparative physiology : A, Neuroethology, sensory, neural, and behavioral physiology N2 - 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. KW - Mormyridae KW - Campylomormyrus KW - Electric organ discharge KW - Electrocyte geometry KW - Electric organ ontogeny Y1 - 2015 U6 - https://doi.org/10.1007/s00359-015-0995-6 SN - 0340-7594 SN - 1432-1351 VL - 201 IS - 4 SP - 357 EP - 374 PB - Springer CY - New York ER - TY - JOUR A1 - Paul, Christiane A1 - Kirschbaum, Frank A1 - Mamonekene, Victor A1 - Tiedemann, Ralph T1 - Evidence for Non-neutral Evolution in a Sodium Channel Gene in African Weakly Electric Fish (Campylomormyrus, Mormyridae) JF - Journal of molecular evolution N2 - 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. KW - Mormyridae KW - Mormyroidea KW - Campylomormyrus KW - SCN4aa KW - Voltage-gated sodium channel KW - Positive selection Y1 - 2016 U6 - https://doi.org/10.1007/s00239-016-9754-8 SN - 0022-2844 SN - 1432-1432 VL - 83 SP - 61 EP - 77 PB - Springer CY - New York ER - TY - JOUR A1 - Nagel, Rebecca A1 - Kirschbaum, Frank A1 - Tiedemann, Ralph T1 - Electric organ discharge diversification in mormyrid weakly electric fish is associated with differential expression of voltage-gated ion channel genes JF - Journal of comparative physiology : A, Neuroethology, sensory, neural, and behavioral physiology N2 - In mormyrid weakly electric fish, the electric organ discharge (EOD) is used for species recognition, orientation and prey localization. Produced in the muscle-derived adult electric organ, the EOD exhibits a wide diversity across species in both waveform and duration. While certain defining EOD characteristics can be linked to anatomical features of the electric organ, many factors underlying EOD differentiation are yet unknown. Here, we report the differential expression of 13 Kv1 voltage-gated potassium channel genes, two inwardly rectifying potassium channel genes, two previously studied sodium channel genes and an ATPase pump in two sympatric species of the genus Campylomormyrus in both the adult electric organ and skeletal muscle. Campylomormyrus compressirostris displays a basal EOD, largely unchanged during development, while C. tshokwe has an elongated, putatively derived discharge. We report an upregulation in all Kv1 genes in the electric organ of Campylomormyrus tshokwe when compared to both skeletal muscle and C. compressirostris electric organ. This pattern of upregulation in a species with a derived EOD form suggests that voltage-gated potassium channels are potentially involved in the diversification of the EOD signal among mormyrid weakly electric fish. KW - Weakly electric fish KW - Ion channels KW - Electric organ KW - Gene expression KW - Campylomormyrus Y1 - 2017 U6 - https://doi.org/10.1007/s00359-017-1151-2 SN - 0340-7594 SN - 1432-1351 VL - 203 SP - 183 EP - 195 PB - Springer CY - New York ER - TY - GEN A1 - Nagel, Rebecca A1 - Kirschbaum, Frank A1 - Engelmann, Jacob A1 - Hofmann, Volker A1 - Pawelzik, Felix A1 - Tiedemann, Ralph T1 - Male-mediated species recognition among African weakly electric fishes T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Effective communication among sympatric species is often instrumental for behavioural isolation, where the failure to successfully discriminate between potential mates could lead to less fit hybrid offspring. Discrimination between con- and heterospecifics tends to occur more often in the sex that invests more in offspring production, i.e. females, but males may also mediate reproductive isolation. In this study, we show that among two Campylomormyrus Africanweakly electric fish species, males preferentially associate with conspecific females during choice tests using live fish as stimuli, i.e. when all sensory modalities potentially used for communication were present. We then conducted playback experiments to determine whether the species-specific electric organ discharge (EOD) used for electrocommunication serves as the cue for this conspecific association preference. Interestingly, only C. compressirostris males associated significantly more with the conspecific EOD waveform when playback stimuli were provided, while no such association preference was observed in C. tamandua males. Given our results, the EOD appears to serve, in part, as a male-mediated pre-zygotic isolation mechanism among sympatric species. However, the failure of C. tamandua males to discriminate between con- and heterospecific playback discharges suggests that multiple modalities may be necessary for species recognition in some African weakly electric fish species. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 645 KW - Campylomormyrus KW - communication KW - electric fishes KW - pre-zygotic isolation KW - species recognition Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-425016 SN - 1866-8372 IS - 645 ER - TY - JOUR A1 - Nagel, Rebecca A1 - Kirschbaum, Frank A1 - Engelmann, Jacob A1 - Hofmann, Volker A1 - Pawelzik, Felix A1 - Tiedemann, Ralph T1 - Male-mediated species recognition among African weakly electric fishes JF - Royal Society Open Science N2 - Effective communication among sympatric species is often instrumental for behavioural isolation, where the failure to successfully discriminate between potential mates could lead to less fit hybrid offspring. Discrimination between con- and heterospecifics tends to occur more often in the sex that invests more in offspring production, i.e. females, but males may also mediate reproductive isolation. In this study, we show that among two Campylomormyrus Africanweakly electric fish species, males preferentially associate with conspecific females during choice tests using live fish as stimuli, i.e. when all sensory modalities potentially used for communication were present. We then conducted playback experiments to determine whether the species-specific electric organ discharge (EOD) used for electrocommunication serves as the cue for this conspecific association preference. Interestingly, only C. compressirostris males associated significantly more with the conspecific EOD waveform when playback stimuli were provided, while no such association preference was observed in C. tamandua males. Given our results, the EOD appears to serve, in part, as a male-mediated pre-zygotic isolation mechanism among sympatric species. However, the failure of C. tamandua males to discriminate between con- and heterospecific playback discharges suggests that multiple modalities may be necessary for species recognition in some African weakly electric fish species. KW - Campylomormyrus KW - communication KW - electric fishes KW - pre-zygotic isolation KW - species recognition Y1 - 2018 U6 - https://doi.org/10.1098/rsos.170443 SN - 2054-5703 VL - 5 IS - 2 PB - Royal Society CY - London ER - TY - JOUR A1 - Lamanna, Francesco A1 - Kirschbaum, Frank A1 - Ernst, Anja R. R. A1 - Feulner, Philine G. D. A1 - Mamonekene, Victor A1 - Paul, Christiane A1 - Tiedemann, Ralph T1 - Species delimitation and phylogenetic relationships in a genus of African weakly-electric fishes (Osteoglossiformes, Mormyridae, Campylomormyrus) JF - Molecular phylogenetics and evolution N2 - 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 mitochondria((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. (C) 2016 Elsevier Inc. All rights reserved. KW - Mormyridae KW - Multispecies-coalescent KW - Campylomormyrus KW - Geometric morphometrics KW - Microsatellites KW - Species-delimitation Y1 - 2016 U6 - https://doi.org/10.1016/j.ympev.2016.04.035 SN - 1055-7903 SN - 1095-9513 VL - 101 SP - 8 EP - 18 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Korniienko, Yevheniia A1 - Tiedemann, Ralph A1 - Vater, Marianne A1 - Kirschbaum, Frank T1 - Ontogeny of the electric organ discharge and of the papillae of the electrocytes in the weakly electric fish Campylomormyrus rhynchophorus (Teleostei: Mormyridae) JF - The journal of comparative neurology N2 - 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 mu m(2)). 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 mu m(2)). 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 mu m(2)). 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 someCampylomormyrusspecies, might be more important concerning the duration of the EOD. KW - Campylomormyrus KW - electric organ discharge KW - electrocyte ontogeny KW - electrocyte ultrastructure KW - papillae Y1 - 2020 U6 - https://doi.org/10.1002/cne.25003 SN - 0021-9967 SN - 1096-9861 VL - 529 IS - 5 SP - 1052 EP - 1065 PB - Wiley CY - Hoboken ER - TY - THES A1 - Feulner, Philine T1 - Adaptive radiation, speciation, and reproductive isolation in African weakly electric fish : (Genus Campylomormyrus, Mormyridae, Teleostei) T1 - Adaptive Radiation, Artbildung und reproduktive Isolation bei schwach elektrischen Fischen Afrikas : (Genus Campylomormyrus, Mormyridae, Teleostei) N2 - The ultimate aim of this study is to better understand the relevance of weak electricity in the adaptive radiation of the African mormyrid fish. The chosen model taxon, the genus Campylomormyrus, exhibits a wide diversity of electric organ discharge (EOD) waveform types. Their EOD is age, sex, and species specific and is an important character for discriminating among species that are otherwise cryptic. After having established a complementary set of molecular markers, I examined the radiation of Campylomormyrus by a combined approach of molecular data (sequence data from the mitochondrial cytochrome b and the nuclear S7 ribosomal protein gene, as well as 18 microsatellite loci, especially developed for the genus Campylomormyrus), observation of ontogeny and diversification of EOD waveform, and morphometric analysis of relevant morphological traits. I built up the first convincing phylogenetic hypothesis for the genus Campylomormyrus. Taking advantage of microsatellite data, the identified phylogenetic clades proved to be reproductively isolated biological species. This way I detected at least six species occurring in sympatry near Brazzaville/Kinshasa (Congo Basin). By combining molecular data and EOD analyses, I could show that there are three cryptic species, characterised by their own adult EOD types, hidden under a common juvenile EOD form. In addition, I confirmed that adult male EOD is species-specific and is more different among closely related species than among more distantly related ones. This result and the observation that the EOD changes with maturity suggest its function as a reproductive isolation mechanism. As a result of my morphometric shape analysis, I could assign species types to the identified reproductively isolated groups to produce a sound taxonomy of the group. Besides this, I could also identify morphological traits relevant for the divergences between the identified species. Among them, the variations I found in the shape of the trunk-like snout, suggest the presence of different trophic specializations; therefore, this trait might have been involved in the ecological radiation of the group. In conclusion, I provided a convincing scenario envisioning an adaptive radiation of weakly electric fish triggered by sexual selection via assortative mating due to differences in EOD characteristics, but caused by a divergent selection of morphological traits correlated with the feeding ecology. N2 - Das übergreifende Ziel dieser Arbeit ist das bessere Verständnis der Bedeutung der schwachen Elektrizität für die adaptive Radiation der Mormyriden Afrikas. Das gewählte Modell-Taxon, die Mormyriden-Gattung Campylomormyrus, zeigt eine große Vielfalt an elektrischen Entladungsformen. Diese Entladungsformen sind alters-, geschlechts-, sowie artspezifisch und ein wichtiges Unterscheidungskriterium von ansonsten kryptischen Arten. Ich untersuchte die Radiation der Gattung Campylomormyrus anhand eines kombinierten Ansatzes aus molekularen Daten (Sequenzdaten des mitochondrialen Cytochrom b Gens und des nukleären S7 ribosomalen Protein-Gens, sowie 18 Mikrosatelliten, speziell von mir entwickelt für die Gattung Campylomormyrus), Beobachtungen der Ontogenie und der Diversifikation der Entladungsform, sowie morphometrische Auswertungen der Gestalt relevanter morphologischer Merkmale. Ich erstellte eine erste phylogenetische Hypothese für die Gattung Campylomormyrus. Durch meine Mikrosatellitendaten, die als unabhängiger Beweis dienten, konnte ich zeigen, dass die identifizierten phylogenetischen Gruppen reproduktiv isolierte biologische Arten sind. Auf diese Weise konnte ich mindesten sechs Arten nachweisen, die in Sympatrie nahe Brazzaville/Kinshasa (Kongo-Becken) vorkommen. Durch die Übereinstimmung von molekularen Daten und Entladungsformen konnte ich drei kryptische Arten unterscheiden, die sich hinter einheitlichen juvenilen Entladungsformen verbergen, sich aber zu verschiedenen adulten Formen entwickelten. Des Weiteren konnte ich zeigen, dass die adulten männlichen Entladungsformen artspezifisch sind und, dass der Unterschied in der Entladungsform zwischen nah verwandten Arten deutlicher ausgeprägt ist als zwischen entfernter verwandten Arten. Dieses Ergebnis und die Beobachtung, dass sich die Entladungsform bei der Geschlechtsreife ändert, weisen darauf hin, dass die Entladungsform als reproduktiver Isolationsmechanismus dient. In einer morphometrischen Gestalt-Analyse verglich ich das Typen-Material der beschriebenen Arten mit den zuvor ermittelten reproduktiv isolierten Gruppen, um auf diese Weise deren Art zu bestimmen. Überdies konnte ich maßgebliche morphologische Unterscheidungsmerkmale identifizieren. Diese äußern sich hauptsächlich in der Gestalt der rüsselartigen Schnauze, könnten daher mit einer trophischen Spezialisierung einhergehen und eine ökologische Artbildung ermöglichen. Zusammenfassend entwickelte ich, in Übereinstimmung mit anderen Untersuchungen und theoretischen Überlegungen, eine plausible Hypothese einer adaptiven Radiation der schwach-elektrischen Fische Afrikas, ausgelöst durch sexuelle Selektion. Diese wirkt durch assortative Verpaarung, basierend auf Charakteristika der elektrischen Entladungsform. Verursacht wird der Prozess der adaptiven Radiation jedoch durch divergierende Selektion morphologischer Merkmale, die in Bezug zur Nahrungsökologie stehen. KW - Phylogenie KW - Ontogenie KW - Morphologie KW - Elektrische Fische KW - Nilhechte KW - Elektrische Entladung KW - Campylomormyrus KW - Mikrosatelliten KW - Campylomormyrus KW - Microsatellite Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-9560 ER -