@article {669, title = {High-frequency electrical tuning and linear filter properties of Knollenorgan electroreceptors of mormyrid electric fish}, journal = {The Journal of Physiology}, year = {2025}, month = {Jun-15-2025}, pages = {1-22}, chapter = {1}, abstract = {

Electrical tuning allows auditory, vestibular, and electrosensory receptor cells to filter sensory signals and selectively transmit specific stimulus frequencies. In auditory hair cells, electrical tuning results from membrane potential resonance produced by voltage-gated Ca and K(Ca) channels, with variable kinetics that generate different tuning properties. Such resonance has been observed only up to \∼1 kHz, however. Additionally, in most species that employ electrical tuning, hearing is constrained to this relatively low-frequency range, raising the question of whether electrical tuning can extend to higher frequencies. Here we investigated this possibility by studying tuning and transduction properties of Knollenorgans, a class of tuberous electroreceptors of mormyrid electric fish. These organs, which generate spike-like receptor potentials, detect species-specific electric organ discharges (EODs). To test whether fish with brief EODs had correspondingly high-frequency electrical tuning, we recorded tuning curves from Knollenorgans of three species, Brevimyrus niger, Gnathonemus petersii, and Pollimyrus adspersus, which have EODs with spectral components exceeding 5 kHz. All species had receptors tuned to a range of frequencies tiling the species-specific EOD spectrum, with best frequencies extending beyond 10 kHz in P. adspersus. We also computed the impulse response of each Knollenorgan by reverse-correlating spikes elicited by white noise stimuli. After incorporation of a spike threshold non-linearity, convolving the impulse response with arbitrary stimulus waveforms successfully predicted spike patterns experimentally evoked by these inputs. These analyses demonstrate that differential electrical tuning properties of Knollenorgans produce distinct, well-timed spike responses that reliably encode time-varying electrical signals at frequencies up to 20 kHz. imageKey points Knollenorgans, among the tuberous electroreceptors of mormyrid electric fish, are modified hair cells that transduce electrical signals into spike-like receptor potentials. Knollenorgans in three species of mormyrids are tuned to frequencies matched to the frequencies present in the species-typical electric organ discharges, suiting them for electric communication. The frequency of highest sensitivity of Knollenorgans can extend well beyond 10 kHz, far exceeding the limit for electrical tuning mechanisms estimated from mechanosensitive hair cells. The timing and probability of spiking by Knollenorgans are accurately predicted by a model composed of linear filtering followed by non-linear rectification and spike thresholding. Differential filtering by different Knollenorgans produces distinct outputs to the same input, with high-tuned receptors effectively transmitting well-timed spikes, on a microsecond time scale, in response to electrical stimuli up to 20 kHz.

}, issn = {0022-3751, 1469-7793}, doi = {10.1113/jp288299}, url = {https://doi.org/10.1113/jp288299}, author = {Raman, Indira M. and Hopkins, Carl D.} } @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} } @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} } @article {622, title = {The electric organ of a mormyrid as a current and voltage source}, journal = {Journal of Comparative Physiology A}, volume = {110}, year = {1976}, month = {Jan-01-1976}, pages = {65-88}, abstract = {

We have examined how the electric organ discharge (EOD) of a mormyrid (Gnathonemus petersii) is affected by changes in resistive load (Figs. 3, 4, 5). We have also shown how this load depends on resistivity and distance to non-conducting boundaries (Figs. 10, 11). When resistive load was varied, voltage and current were related in a linear, battery-like manner for the initial, head positive phase of the EOD (Figs. 4, 5). This linear relation made it possible to estimate first phase e.m.f, and source resistance. For the second, head negative phase, however, voltage rose to a peak and then fell as resistance increased. Furthermore, the waveform of the second but not the first phase was strongly affected by load changes. These second phase features were shown to reflect a dependence of second phase e.m.f, on first phase current. A linear and battery-like relation between second phase voltage and current was seen when first phase load was held constant while varying second phase load (Fig. 6). These results on the behavior of the whole electric organ can be understood in terms of the underlying properties of the cellular generators, the electrocytes

}, keywords = {conductivity, electrocyte, EOD, eod waveform}, issn = {0302-9824}, doi = {10.1007/bf00656782}, url = {http://dx.doi.org/10.1007/bf00656782}, author = {Bell, C. C. and Bradbury, J. and Russell, C. J.} } @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 {604, title = {Die Schnauzenorgane der Mormyriden}, journal = {Zeitschrift f{\"u}r wissenschaftliche Zoologie}, volume = {115}, year = {1916}, pages = {650-670, Pl. VII}, chapter = {650}, url = {https://www.biodiversitylibrary.org/page/9753601}, author = {Stendell, W.} } @article {542, title = {Object discrimination through active electrolocation: Shape recognition and the influence of electrical noise}, journal = {Journal of Physiology-Paris}, year = {2016}, month = {Jan-12-2016}, abstract = {

The weakly electric fish Gnathonemus petersii can recognise objects using active electrolocation. Here, we tested two aspects of object recognition; first whether shape recognition might be influenced by movement of the fish, and second whether object discrimination is affected by the presence of electrical noise from conspecifics. (i) Unlike other object features, such as size or volume, no parameter within a single electrical image has been found that encodes object shape. We investigated whether shape recognition might be facilitated by movement-induced modulations (MIM) of the set of electrical images that are created as a fish swims past an object. Fish were trained to discriminate between pairs of objects that either created similar or dissimilar levels of MIM of the electrical images. As predicted, the fish were able to discriminate between objects up to a longer distance if there was a large difference in MIM between the objects than if there was a small difference. This supports an involvement of MIMs in shape recognition but the use of other cues cannot be excluded. (ii) Electrical noise might impair object recognition if the noise signals overlap with the EODs of an electrolocating fish. To avoid jamming, we predicted that fish might employ pulsing strategies to prevent overlaps. To investigate the influence of electrical noise on discrimination performance, two fish were tested either in the presence of a conspecific or of playback signals and the electric signals were recorded during the experiments. The fish were surprisingly immune to jamming by conspecifics: While the discrimination performance of one fish dropped to chance level when more than 22\% of its EODs overlapped with the noise signals, the performance of the other fish was not impaired even when all its EODs overlapped. Neither of the fish changed their pulsing behaviour, suggesting that they did not use any kind of jamming avoidance strategy.

}, issn = {09284257}, doi = {10.1016/j.jphysparis.2016.11.008}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0928425716300304}, author = {Schumacher, Sarah and Burt de Perera, Theresa and G. von der Emde} } @article {540, title = {Sensory flow as a basis for a novel distance cue in freely behaving electric fish}, journal = {Journal of Neuroscience}, year = {2016}, month = {Nov-24-2016}, abstract = {

ABSTRACT

The sensory input that an animal receives is directly linked to its motor activity. Behavior thus enables animals to influence their sensory input, a concept referred to as active sensing. How such behavior can serve as a scaffold for generating sensory information is of general scientific interest. In this article, we investigate how behavior can shape sensory information by using some unique features of the sensorimotor system of the weakly electric fish.

Based on quantitative behavioral characterizations and computational reconstruction of sensory input, we show how electrosensory flow is actively created during highly patterned, spontaneous behavior in Gnathonemus petersii. The spatiotemporal structure of the sensory input provides information for the computation of a novel distance cue, which allows for a continuous estimation of distance. This has significant advantages over previously known non-dynamic distance estimators as determined from electric image blur.

Our investigation of the sensorimotor interactions in pulsatile electrolocation show, for the first time, that the electrosensory flow contains behaviorally relevant information only accessible through active behavior. As patterned sensory behaviors are a shared feature of (active) sensory systems, our results have general implications for the understanding of (active) sensing, with the proposed sensory flow based-measure being potentially pertinent to a broad range of sensory modalities.

SIGNIFICANCE STATEMENT

Acquisition of sensory information depends on motion, as either an animal or its sensors move. Behavior can thus actively influence the sensory flow, and in this way, behavior can be seen as a manifestation of the brain\&$\#$39;s integrative functions. The properties of the active pulsatile electrolocation system in Gnathonemus petersii allow for the sensory input to be computationally reconstructed, enabling us to link the informational content of spatiotemporal sensory dynamics to behavior. Our study reveals a novel sensory cue for estimating depth that is actively generated by the fishes\&$\#$39; behavior. The physical and behavioral similarities between electrolocation and other active sensory systems suggest that this may be a mechanism shared by (active) sensory systems.

}, issn = {0270-6474}, doi = {10.1523/JNEUROSCI.1361-16.2016}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.1361-16.2016}, author = {Hofmann, V. and Sanguinetti-Scheck, J. I. and Gomez-Sena, L. and Engelmann, J.} } @article {475, title = {The anal fin complex in a weakly discharging electric fish, Gnathonemus petersii(Mormyridae)}, journal = {Journal of Fish Biology}, volume = {66}, year = {2005}, month = {Jan-01-2005}, pages = {266 - 275}, abstract = {

An examination of the permanent bony structures of the anal fin complex in the mormyrid fish, Gnathonemus petersii, revealed two new structural sexual dimorphisms: longer proximal pterygiophores and wider anal fin rays in males than in females. Both structures are thought to facilitate the male\’s courtship-associated anal fin reflex. Adult male mormyrid fishes are characterized by a dorsally directed indentation of the posterior body wall (anal fin indentation). The expression of this indentation in males, presumably driven by anal fin musculature, was correlated with the fish\’s gonadal state: large indentations were associated with high gonado-somatic indices and small indentations with low indices.

}, issn = {0022-1112}, doi = {10.1111/jfb.2005.66.issue-110.1111/j.0022-1112.2005.00608.x}, url = {http://www.blackwell-synergy.com/toc/jfb/66/1}, author = {Greisman, L. and Moller, P.} } @article {474, title = {A sexually dimorphic basal anal-fin ray expansion in the weakly discharging electric fish Gnathonemus petersii}, journal = {Journal of Fish Biology}, volume = {53}, year = {1998}, month = {Jan-09-1998}, pages = {638 - 644}, abstract = {

Male Gnathonemus petersii (Mormyridae) exhibit two structural, sexually dimorphic characters: anal-fin ray bone expansion and an indentation of the posterior ventral body wall (formerly described as anal-fin indentation). Females lack this bone expansion, but may show a slight indentation. Morphometric data on both characters were obtained from radiographs of 414 fish (males and females) ranging in size from 60 to 276 mm Ls. Both body wall indentation and bone expansion began to develop in males of about 120 mm Ls. At 160\–180 mm, the sex ratio of fish with expansion to fish without expansion was 50 : 50. Androgens seem to affect the expression of both these sexual dimorphisms. Bone expansion may provide increased bone surface for muscle attachment and thus facilitate the anal-fin reflex during courtship behaviour.

}, issn = {0022-1112}, doi = {10.1111/jfb.1998.53.issue-310.1111/j.1095-8649.1998.tb01007.x}, url = {http://www.blackwell-synergy.com/toc/jfb/53/3}, author = {Pezzanite, B. and Moller, P.} } @article {cite-key, title = {Eine neue art von Mormyrus}, journal = {Archiv f{\"u}r Naturgeschichte}, volume = {28}, number = {1}, year = {1862}, pages = {64}, keywords = {Mormyrus petersii}, url = {http://biodiversitylibrary.org/page/7160516}, author = {G{\"u}nther, Albert C. L. G.} } @article {608, title = {A revision of the genera and species of fishes of the family Mormyridae}, journal = {Proceedings of the General Meetings for Scientific Business of the Zoological Society of London}, volume = {1898}, number = {Part 4}, year = {1899}, pages = {775-821}, url = {http://www.biodiversitylibrary.org/item/97095$\#$page/919/mode/1up}, author = {George A. Boulenger} } @inbook {121, title = {Catalogue of the Fresh-Water Fishes of Africa in the British Museum (Natural History)}, booktitle = {Catalogue of the Fresh-Water Fishes of Africa in the British Museum (Natural History)}, volume = {I}, year = {1909}, pages = {29-145}, publisher = {British Museum (Natural History)}, organization = {British Museum (Natural History)}, address = {London}, url = {https://biodiversitylibrary.org/page/37889609}, author = {George A. Boulenger} } @article {388, title = {Poissons du Gribingui recueillis par M. Baudon. Description de sept esp{\`e}ces nouvelles}, journal = {Bulletin de la Soci{\'e}t{\'e} Zoologique de France}, volume = {44}, number = {201{\textendash}214}, year = {1919}, pages = {201{\textendash}214}, chapter = {201}, url = {http://biodiversitylibrary.org/page/35980788}, author = {Pellegrin, J.} } @article {262, title = {Zoological results of the George Vanderbilt African Expedition of 1934. Part III,{\textendash}The fresh water fishes}, journal = {Proceedings of the Academy of Natural Sciences of Philadelphia}, volume = {88}, year = {1936}, month = {07/1936}, pages = {243{\textendash}335}, abstract = {

The Academy is fortunate in securing the very interesting collection obtained by this expedition. Considering the wide range of localities or stations across transcontinental Africa, of which 39 are listed in part 1 of the present series of papers,\’ only 7 yielded fishes. These are: (13) Athi River Crossing, (17) Kitala, (23) Saidi\’s Village, (24) Vube, (26) Eki- bondo\’s Village, (27) Fort Sibut and (33) Nola. Other smaller lots of materials were later received from 30 kilometers east of Kribi, Cameroons, and Batangafo, Chad Basin. The specimens number nearly 3000, representing 115 species, of which 10 are described as new genera or subgenera and 36 as new species or sub- species. This is surely a remarkable showing, especially in view of the comparatively short amount of time available and the mobility of the expedition. To Mr. George Vanderbilt is due special acknowledgment for his per- sonal interest in the collecting of the specimens, and amassing comprehen- sive series for the museum of the Academy.

}, author = {Fowler, H.W.} } @article {622, title = {Pesci raccolti dal March. Saverio Patrizi nel bacino del Congo}, journal = {Annali del Museo Civico di Storia Naturale {\textquoteleft}Giacomo Doria{\textquoteright}}, volume = {53}, year = {1928}, month = {08/1928}, pages = {1{\textendash}28}, author = {Vinciguerra, D.} } @article {260, title = {Contribution {\`a} la faune ichthyologique du Congo Belge: Collections du Dr. H. Schouteden (1924-1926) et d{\textquoteright}autres r{\'e}colteurs}, journal = {Annales du Mus{\'e}e du Congo Belge (S{\'e}rie 1)}, volume = {3 (fasc. 5)}, year = {1937}, month = {05/1937}, pages = {189{\textendash}294}, author = {David, L. and Poll, M.} } @article {832, title = {Les poissons du bassin du Tchad et du bassin adjacent du Mayo Kebbi {\'e}tude syst{\'e}matique et biologique}, year = {1964}, pages = {1{\textendash}483}, publisher = {ORSTOM}, address = {Paris}, url = {http://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_2/memoires/19994.pdf}, author = {Blache, J.} } @article {144, title = {Les Poissons du Stanley-Pool}, journal = {Annales du Mus{\'e}e du Congo belge. C.{\textendash}Zoologie S{\'e}rie I.}, volume = {4}, number = {1}, year = {1939}, month = {12/1939}, pages = {1-60}, chapter = {1}, author = {Poll, M.} } @book {213, title = {Contribution {\`a} la Faune Ichthyologique de l{\textquoteright}Angola}, series = {Publica{\c c}{\~o}es Culturais}, number = {75}, year = {1967}, pages = {381}, publisher = {Companhia de Diamantes de Angola (DIAMANG)}, organization = {Companhia de Diamantes de Angola (DIAMANG)}, address = {Lisbon}, keywords = {Angola}, author = {Poll, M.} } @article {180, title = {Mise en synonymie de Gnathonemus brevicaudatus Pellegrin, 1919 avec Gnathonemus petersii Gunther, 1862 (Teleostei, Mormyridae)}, journal = {Cybium}, volume = {14}, number = {2}, year = {1990}, pages = {125-129}, author = {Bigorne, R.} } @inbook {179, title = {Mormyridae}, booktitle = {Faune des poissons d{\textquoteright}eaux douces et saum{\^a}tres de l{\textquoteright}Afrique de l{\textquoteright}Ouest = The fresh and brackish water fishes of West Africa}, series = {Faune tropicale 28}, year = {1990}, pages = {122-184}, publisher = {ORSTOM, MRAC}, organization = {ORSTOM, MRAC}, address = {Paris, Tervuren (Belgium)}, url = {http://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_6/Fau_trop/34060.pdf}, author = {Bigorne, R.}, editor = {L{\'e}v{\^e}que, C. and Paugy, D. and Teugels, G.G.} } @inbook {158, title = {Mormyridae}, booktitle = {Faune des poissons d{\textquoteright}eaux douces et saum{\^a}tres de l{\textquoteright}Afrique de l{\textquoteright}Ouest}, volume = {1}, year = {2003}, pages = {154-222}, publisher = {IRD/MNHN/MRAC}, organization = {IRD/MNHN/MRAC}, url = {http://www.ird.fr/editions/catalogue/ouvrage.php?livre=409}, author = {Bigorne, R.} } @book {159, title = {The Mormyridae and other Osteoglossomorpha (CD-ROM)}, series = {World Biodiversity Database, CD-ROM Series}, volume = {2000}, year = {2000}, publisher = {Springer Verlag, ETI-UNESCO}, organization = {Springer Verlag, ETI-UNESCO}, address = {New York}, issn = {Hyb: 3-540-14811-6}, url = {https://www.amazon.com/Mormyridae-Osteoglossomorpha-Biodiversity-Database-CD-ROM/dp/3540148116}, author = {Harder, W.} } @inbook {152, title = {12. Mormyridae}, booktitle = {The Fresh and Brackish Water Fishes of Lower Guinea, West-Central Africa}, series = {Collection Faune et Flore Tropicales 42}, volume = {1}, year = {2007}, pages = {220{\textendash}334}, publisher = {IRD}, organization = {IRD}, chapter = {12}, isbn = {978-2-7099-1621-9}, author = {Carl D Hopkins and S{\'e}bastien Lavou{\'e} and John P Sullivan}, editor = {Melanie L.J. Stiassny and Teugels, G.G. and Carl D Hopkins} }