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/jp28829902463nas a2200157 4500008004100000022002500041245016500066210006900231260001600300520186800316100001602184700002202200700002202222700002102244856004002265 2023 eng d a0962-1083, 1365-294X00aDiet in phenotypically divergent sympatric species of African weakly electric fish (genus: Campylomormyrus)—A hybrid capture/HTS metabarcoding approach0 aDiet in phenotypically divergent sympatric species of African we cDec-21-20233 a

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.

1 aAmen, Rahma1 aHavenstein, Katja1 aKirschbaum, Frank1 aTiedemann, Ralph uhttp://dx.doi.org/10.1111/mec.1724801927nas a2200157 4500008004100000022001400041245006100055210006100116260001600177490000600193520147300199100001901672700001601691700002001707856004201727 2023 eng d a2517-484300aHistology of Convergent Probing Appendages in Mormyridae0 aHistology of Convergent Probing Appendages in Mormyridae cJan-01-20230 v53 a

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.

1 aPeterson, Rose1 aEvans, A, J1 aHernandez, L, P uhttp://dx.doi.org/10.1093/iob/obad00101771nas a2200217 4500008004100000022001400041245006900055210006500124260001600189300001000205490000800215520117700223653001701400653001601417653000801433653001701441100001701458700001701475700002001492856004101512 1976 eng d a0302-982400aThe electric organ of a mormyrid as a current and voltage source0 aelectric organ of a mormyrid as a current and voltage source cJan-01-1976 a65-880 v1103 a

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

10aconductivity10aelectrocyte10aEOD10aeod waveform1 aBell, C., C.1 aBradbury, J.1 aRussell, C., J. uhttp://dx.doi.org/10.1007/bf0065678200858nas 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.5607702035nas a2200157 4500008004100000022002500041245019500066210006900261260001600330300001200346490000900358520142900367100001501796700001801811856004801829 2022 eng d a1175-5334, 1175-532600aMarcusenius elegans: a replacement name for Marcusenius gracilis Kramer 2013 (Osteoglossiformes: Mormyridae), a secondary junior homonym of Marcusenius senegalensis gracilis (Pellegrin 1922)0 aMarcusenius elegans a replacement name for Marcusenius gracilis  cAug-18-2022 a499-5000 v51753 a

The West African mormyrid Marcusenius gracilis Kramer 2013 is a secondary homonym of Gnathonemus gracilis Pellegrin 1922 when both species are placed in the same genus Marcusenius (International Code of Zoological Nomenclature, article 57.3). Marcusenius gracilis was first described by Kramer (2013: 123), based on a holotype and 16 paratypes from Ivory Coast, West Africa. The taxon was subsequently treated as a valid species of Marcusenius by Kramer & Wink (2013: 2334), and by Fricke et al. (2022). Kramer (2013) was not aware of Gnathonemus gracilis Pellegrin 1922, which was originally described by Pellegrin (1922: 221), based on a specimen from the Gribingui River, Lake Chad basin, in today’s Central African Republic. The holotype is extant (MNHN 1922-0023). The taxon was treated as a synonym of the West African species Marcusenius senegalensis (Steindachner 1870), but as a valid subspecies (Gosse 1984: 89, Lévêque et al. 1991: 138). Marcusenius senegalensis gracilis (Pellegrin 1922) has precedence over Marcusenius gracilis Kramer 2013, and the latter must be renamed when both taxa are classified in genus Marcusenius. Marcusenius elegans nom. nov. is herein proposed as the replacement name for Marcusenius gracilis Kramer 2013. The new species epithet is based on the Latin word elegans, meaning elegant, referring to its slender body; the name is treated as an adjective.

1 aFricke, R.1 aKramer, Bernd uhttp://dx.doi.org/10.11646/zootaxa.5175.4.801616nas a2200169 4500008004100000022001400041245015000055210006900205260001600274520099000290100002601280700002501306700002001331700002101351700002201372856005201394 2022 eng d a1432-135100aIntergenus F1-hybrids of African weakly electric fish (Mormyridae: Gnathonemus petersii ♂ × Campylomormyrus compressirostris ♀) are fertile.0 aIntergenus F1hybrids of African weakly electric fish Mormyridae  c2022 Feb 043 a

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.

1 aKorniienko, Yevheniia1 aNzimora, Kingsley, C1 aVater, Marianne1 aTiedemann, Ralph1 aKirschbaum, Frank uhttps://mormyrids.efishgenomics.com/en/node/60800328nas a2200109 4500008004100000245003900041210003900080300002100119490000800140100001700148856005300165 1916 eng d00aDie Schnauzenorgane der Mormyriden0 aDie Schnauzenorgane der Mormyriden a650-670, Pl. VII0 v1151 aStendell, W. uhttps://www.biodiversitylibrary.org/page/975360103057nas a2200313 4500008004100000022001300041245015100054210006900205260001600274520202800290653002802318653002002346653002802366653001202394653001402406100002202420700001702442700002702459700001502486700001802501700002302519700002102542700002602563700002402589700002302613700002002636700002102656856006602677 2017 eng d a0928425700aIntragenus (Campylomormyrus) and intergenus hybrids in mormyrid fish: physiological and histological investigations of the electric organ ontogeny0 aIntragenus Campylomormyrus and intergenus hybrids in mormyrid fi cJan-01-20173 a

African weakly electric mormyrid fish show a high diversity of their electric organ discharge (EOD) both across and within genera. Thanks to a recently developed technique of artificial reproduction in mormyrid fish, we were able to perform hybridizations between different genera and within one genus (Campylomormyrus). The hybrids of intergenus hybridizations exhibited different degrees of reduced survival related to the phylogenetic distance of the parent species: hybrids of the crosses between C. rhynchophorus and its sister genus Gnathonemus survived and developed normally. Hybrids between C. rhynchophorus and a Mormyrus species (a more basal clade compared to Campylomormyrus s) survived up to 42 days and developed many malformations, e.g., at the level of the unpaired fins. Hybrids between C. numenius and Hippopotamyrus pictus (a derived clade, only distantly related to Campylomormyrus) only survived for two days during embryological development. Seven different hybrid combinations among five Campylomormyrus species (C. tamandua, C. compressirostris, C. tshokwe, C. rhynchophorus, C. numenius) were performed. The aim of the hybridizations was to combine species with (1) either caudal or rostral position of the main stalk innervating the electrocytes in the electric organ and (2) short, median or long duration of their EOD. The hybrids, though they are still juveniles, show very interesting features concerning electrocyte geometry as well as EOD form and duration: the caudal position of the stalk is prevailing over the rostral position, and the penetration of the stalk is dominant over the non-penetrating feature (in the Campylomormyrus hybrids); in the hybrid between C. rhynchophorus and Gnathonemus petersii it is the opposite. When crossing species with long and short EODs, it is always the long duration EOD that is expressed in the hybrids. The F1-Hybrids of the cross C. tamandua x C. compressirostris are fertile: viable F2-fish could be obtained with artificial reproduction

10aArtificial reproduction10aCampylomormyrus10aElectric organ ontogeny10aHybrids10amormyrids1 aKirschbaum, Frank1 aNguyen, Linh1 aBaumgartner, Stephanie1 aChi, Linda1 aWolfart, Rene1 aElarbani, Khouloud1 aEppenstein, Hari1 aKorniienko, Yevheniia1 aGuido-Böhm, Lilian1 aMamonekene, Victor1 aVater, Marianne1 aTiedemann, Ralph uhttp://linkinghub.elsevier.com/retrieve/pii/S092842571730003702502nas a2200145 4500008004100000022001300041245011400054210006900168260001600237520196500253100002202218700002902240700002102269856006602290 2016 eng d a0928425700aObject discrimination through active electrolocation: Shape recognition and the influence of electrical noise0 aObject discrimination through active electrolocation Shape recog cJan-12-20163 a

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.

1 aSchumacher, Sarah1 ade Perera, Theresa, Burt1 avon der Emde, G. uhttp://linkinghub.elsevier.com/retrieve/pii/S092842571630030402878nas a2200157 4500008004100000022001400041245008600055210006900141260001600210520234200226100001602568700003102584700001902615700001802634856006802652 2016 eng d a0270-647400aSensory flow as a basis for a novel distance cue in freely behaving electric fish0 aSensory flow as a basis for a novel distance cue in freely behav cNov-24-20163 a

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'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' 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.

1 aHofmann, V.1 aSanguinetti-Scheck, J., I.1 aGomez-Sena, L.1 aEngelmann, J. uhttp://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.1361-16.201601242nas a2200157 4500008004100000022001400041245009700055210006900152260001600221300001400237490000700251520074400258100001701002700001501019856005001034 2005 eng d a0022-111200aThe anal fin complex in a weakly discharging electric fish, Gnathonemus petersii(Mormyridae)0 aanal fin complex in a weakly discharging electric fish Gnathonem cJan-01-2005 a266 - 2750 v663 a

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.

1 aGreisman, L.1 aMoller, P. uhttp://www.blackwell-synergy.com/toc/jfb/66/101371nas a2200157 4500008004100000022001400041245011500055210006900170260001600239300001400255490000700269520085400276100001801130700001501148856005001163 1998 eng d a0022-111200aA sexually dimorphic basal anal-fin ray expansion in the weakly discharging electric fish Gnathonemus petersii0 asexually dimorphic basal analfin ray expansion in the weakly dis cJan-09-1998 a638 - 6440 v533 a

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.

1 aPezzanite, B.1 aMoller, P. uhttp://www.blackwell-synergy.com/toc/jfb/53/300553nas 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/446