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/jp28829902820nas a2200253 4500008004100000022002500041245010600066210006900172260001600241300000900257490000900266520199800275653001502273653003602288653003202324653003302356653003002389653001302419100002202432700003402454700001702488700002102505856004002526 2024 eng d a0022-1112, 1095-864900aMorphometric synthesis of Pollimyrus (Teleostei, Mormyridae) with the description of four new species0 aMorphometric synthesis of Pollimyrus Teleostei Mormyridae with t cNov-24-2024 a1-470 v20243 a

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.

10amorphology10aPollimyrus ibalazambai sp. nov.10aPollimyrus krameri sp. nov.10aPollimyrus vanneeri sp. nov.10aPollimyrus weyli sp. nov.10aTaxonomy1 aDierickx, Katrien1 aLunkayilakio, Soleil, Wamuini1 aBills, Roger1 aVreven, Emmanuel uhttp://dx.doi.org/10.1111/jfb.1598302236nas a2200157 4500008004100000245011400041210006900155260001600224300001400240490000800254520161500262100002001877700002001897700002301917856013801940 1997 eng d00aSound Production and Reproductive Ecology of Strongly Acoustic Fish in Africa: Pollimyrus isidori, Mormyridae0 aSound Production and Reproductive Ecology of Strongly Acoustic F cJan-01-1997 a677 - 7250 v1343 a

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.

1 aBenech, Vincent1 aJacob, Philippe1 aCrawford, John, D. uhttps://brill.com/view/journals/beh/134/9-10/article-p677_3.xmlhttps://data.brill.com/files/journals/1568539x_134_09-10_s003_text.pdf