04147nas a2200145 4500008004100000022002500041245012700066210007100193260001600264300000900280520363100289100002203920700002203942856003703964 2025 eng d a0022-3751, 1469-779300aHigh‐frequency electrical tuning and linear filter properties of Knollenorgan electroreceptors of mormyrid electric fish0 aHigh‐frequency electrical tuning and linear filter properties of cJun-15-2025 a1-223 a

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.

1 aRaman, Indira, M.1 aHopkins, Carl, D. uhttps://doi.org/10.1113/jp28829902411nas a2200241 4500008004100000022001400041245014100055210006900196260001600265300001200281490000900293520162800302653002101930653002701951653001501978653003701993653002002030100001902050700001602069700001402085700001802099856005202117 2025 eng d a2658-351800aLength-weight relationships and condition factors of Mormyridae species in the Niger River: implications for conservation and management0 aLengthweight relationships and condition factors of Mormyridae s cJan-01-2025 a215-2210 v20253 a

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.

10acondition factor10alength-weight analysis10aMormyridae10asustainable fisheries management10athe Niger River1 aSouley, S.M.N.1 aHarouna, M.1 aAdo, M.I.1 aYoussoufa, I. uhttps://doi.org/10.31951/2658-3518-2025-a-2-21500858nas a2200145 4500008004100000022001400041245009800055210006900153260001600222520037400238100001900612700002200631700001700653856004200670 2022 eng d a2687-794500aThe Complete Genome Sequences of 38 Species of Elephantfishes (Mormyridae, Osteoglossiformes)0 aComplete Genome Sequences of 38 Species of Elephantfishes Mormyr cNov-21-20223 a

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.

1 aPeterson, Rose1 aSullivan, John, P1 aPirro, Stacy uhttp://dx.doi.org/10.56179/001c.5607700914nas a2200121 4500008004100000245010500041210006900146260001600215520048500231100001800716700001500734856004300749 2016 eng d00aAnal-fin ray morphology indicates sexual maturity in Brevimyrus niger (Teleostei, Mormyridae)0 aAnalfin ray morphology indicates sexual maturity in iBrevimyrus  cJan-10-20163 a

This osteological survey of 249 specimens of Brevimyrus niger ranging in size from 44 to 137 mm standard length (LS) demonstrated that developmental changes in anal-fin morphology can serve as a predictor of sexual maturity in this species. Anal-fin ray bases begin to expand when fish reach c. 90 mm LS at which size and above there were roughly equal numbers of individuals observed with expanded and unmodified anal-fin bases, reflecting a 1:1 sex ratio.

1 aStell, S., K.1 aMoller, P. uhttp://doi.wiley.com/10.1111/jfb.1316300837nas a2200157 4500008004100000022001400041245008400055210006900139260001600208300001400224490000700238520029300245100001500538700002300553856010300576 2007 eng d a0022-111200aThe air-breathing behaviour of Brevimyrus niger (Osteoglossomorpha, Mormyridae)0 aairbreathing behaviour of Brevimyrus niger Osteoglossomorpha Mor cJan-07-2007 a279 - 2830 v713 a

Brevimyrus niger is reported to breathe atmospheric air, confirming previous documentation of air breathing in this species. Air is taken up by rising to the water surface and gulping, or permanently resting just below the surface, depending on the environmental conditions.

1 aMoritz, T.1 aLinsenmair, K., E. uhttp://www.blackwell-synergy.com/toc/jfb/71/1http://doi.wiley.com/10.1111/j.1095-8649.2007.01473.x00553nas a2200121 4500008004100000245021100041210007100252260001200323300001100335490001700346100001600363856005200379 1971 eng d00aNote sur la systématique des poissons Mormyriformes. Le problème des genres Gnathonemus Gill, Marcusenius Gill, Hippopotamyrus Pappenheim, Cyphomyrus Myers et les nouveaux genres Pollimyrus et Brienomyrus0 aNote sur la systématique des poissons Mormyriformes Le problème  c09/1971 a99-1100 v84 (pts 1-2)1 aTaverne, L. uhttps://mormyrids.efishgenomics.com/en/node/44600469nas a2200133 4500008004100000245010400041210007000145300001200215490000700227100001500234700001500249700002000264856005100284 1973 eng d00aContribution a l’étude de la faune ichthyologique du bassin du fleuve Sénégal. III. Mormyridae0 aContribution a l étude de la faune ichthyologique du bassin du f a665-7040 v351 aReizer, C.1 aMattei, X.1 aChevalier, J.L. uhttps://mormyrids.efishgenomics.com/en/node/98