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  - 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  -