@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 {662, title = {Morphometric synthesis of Pollimyrus (Teleostei, Mormyridae) with the description of four new species}, journal = {Journal of Fish Biology}, volume = {2024}, year = {2024}, month = {Nov-24-2024}, pages = {1-47}, abstract = {

Mormyridae, a species-rich family endemic to Africa, remains taxonomically understudied. This has been the case for the genus Pollimyrus Taverne, 1971, which hinders further understanding of the distribution, ecology, and conservation of its species. Therefore, an in-depth morphometric comparison of all currently valid species is carried out using most of the available type specimens. Species delineations were re-evaluated, and four species new to science described: Pollimyrus ibalazambai sp. nov. (the Luki River, the Democratic Republic of the Congo), Pollimyrus krameri sp. nov. (the Lugenda River, Mozambique), Pollimyrus vanneeri sp. nov. (the Kouilou-Niari River, the Republic of the Congo), and Pollimyrus weyli sp. nov. (the Buzi River, Mozambique). In this study, Pollimyrus guttatus is confirmed to belong to Pollimyrus, whereas Pollimyrus eburneensis and Cyphomyrus plagiostoma seem more similar to species allocated to other genera. No or only little morphological differences were found between the type series of several species, which could indicate the need for synonymization of these species (Pollimyrus cuandoensis with Pollimyrus marianne and Pollimyrus nigripinnis with Pollimyrus pulverulentus). As such 20 species are currently morphologically identifiable in the genus Pollimyrus. The present study highlights the critical need for further synthetic efforts and new collecting efforts across Africa for this and other Mormyridae genera.

}, keywords = {morphology, Pollimyrus ibalazambai sp. nov., Pollimyrus krameri sp. nov., Pollimyrus vanneeri sp. nov., Pollimyrus weyli sp. nov., Taxonomy}, issn = {0022-1112, 1095-8649}, doi = {10.1111/jfb.15983}, url = {http://dx.doi.org/10.1111/jfb.15983}, author = {Dierickx, Katrien and Wamuini Lunkayilakio, Soleil and Bills, Roger and Vreven, Emmanuel} } @article {585, title = {Sound Production and Reproductive Ecology of Strongly Acoustic Fish in Africa: Pollimyrus isidori, Mormyridae}, journal = {Behaviour}, volume = {134}, year = {1997}, month = {Jan-01-1997}, pages = {677 - 725}, abstract = {

We have studied the reproductive ecology and bioacoustic signals of weakly electric mormyrid fish in Africa in order to discover the natural conditions under which acoustic signals are used and to gain insight into the evolution of their acoustic behaviour and hearing. Pollimyrus\ isidori migrated from a tributary of the Niger River (Mali) into a shallow (2- 3 m) flood plain during the onset of the flooding seasons (August, 1991 and 1994). The\ fish were fully primed for reproduction upon entering the plain, females were significantly larger than males, and the sex ratio was skewed toward males (about 2 males per female). Males established territories (d \≈ 1 m) within the roots of floating rafts of grasses, about 0.5 m below the water surface. Males produced conspicuous acoustic displays consisting of Grunts and Moans during the night (130 dB peak re 1 \μLPaat approximately 10 cm). These sounds had a fundamental of 340 Hz, but the band-width of the grunt extended to over 3 kHz. Experiments at the field site with captive animals showed that male sound production was stimulated by the presence of conspecific females. The P. isidori repertoire included 3 additional sounds. Analysis of environmental noise showed that these communication sounds fall within a distinct spectral window, thereby minimizing potential interference from other aquatic animals and abiotic noise sources. Waveform analyses showed that the sounds remained coherent over short distances (0.5 m) but lost amplitude more rapidly than would be predicted in a deep water free-field.

}, doi = {10.1163/156853997X00034}, url = {https://brill.com/view/journals/beh/134/9-10/article-p677_3.xmlhttps://data.brill.com/files/journals/1568539x_134_09-10_s003_text.pdf}, author = {Benech, Vincent and Jacob, Philippe and Crawford, John D.} } @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 {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} } @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.} } @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.} } @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.} } @article {156, title = {R{\'e}vision syst{\'e}matique du genre Pollimyrus (Teleostei, Mormyridae) en Afrique de l{\textquoteright}Ouest}, journal = {Revue d{\textquoteright}Hydrobiologie Tropicale}, volume = {23}, number = {4}, year = {1990}, pages = {313-327}, chapter = {313}, author = {Bigorne, R.} } @article {351, title = {Electrosensory basis for individual recognition in a weakly electric, mormyrid fish, Pollimyrus adspersus (G{\"u}nther, 1866)}, journal = {Behavioral Ecology and Sociobiology}, volume = {55}, year = {2003}, month = {12/2003}, pages = {197 - 208}, issn = {1432-0762}, doi = {10.1007/s00265-003-0690-4}, author = {Paintner, Stephan and Bernd Kramer} } @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} }