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Journal articles on the topic 'Eigenmannia'

Author: Grafiati

Published: 4 June 2021

Last updated: 8 February 2022

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1

Silva, Danillo S., Luiz A. W. Peixoto, Julio C. Pieczarka, Wolmar B. Wosiacki, Jonathan S. Ready, and Cleusa Y. Nagamachi. "Karyotypic and morphological divergence between two cryptic species of Eigenmannia in the Amazon basin with a new occurrence of XX/XY sex chromosomes (Gymnotiformes: Sternopygidae)." Neotropical Ichthyology 13, no. 2 (June 2015): 297–308. http://dx.doi.org/10.1590/1982-0224-20140160.

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Eigenmannia species are widely distributed in the Neotropics, with eight valid species currently recognized. Populations of Eigenmannia from three locations in the eastern Amazon were investigated using cytogenetic and morphological techniques, revealing two taxa designated here as Eigenmannia sp. "A" and Eigenmannia sp. "B". The species differ in three morphometric characters, two meristic characters, and one osteological character. Eigenmannia sp. "A" presents 2n = 34 (22 m/sm+12 st/a) and Eigenmannia sp. "B" presents 2n = 38 (14 m/sm+24st/a) and simple differentiated sex chromosomes of the type XX/XY. In both species the Constitutive Heterochromatin (CH) rich in A-T bases is distributed in the centromeric region of all chromosomes. Eigenmannia sp. "B" also presents CH blocks in the interstitial region of chromosome pairs 8, 9 and X which are positively stained with CMA3, indicating G-C rich regions. The NOR is located on the short arm of chromosome pair 17 of Eigenmannia sp. "A" and on the short arm of pair 14 of Eigenmannia sp. "B". FISH with rDNA probes hybridized to different-sized regions between homologs, suggesting heteromorphism. The differentiation of the X chromosome in Eigenmannia sp. "B" could be the result of amplification of repetitive DNA sequences.

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2

CAMPOS-DA-PAZ, RICARDO, and IGOR RAPOSO QUEIROZ2. "A new species of Eigenmannia Jordan and Evermann (Gymnotiformes: Sternopygidae) from the upper rio Paraguai basin." Zootaxa 4216, no. 1 (January 3, 2017): 73. http://dx.doi.org/10.11646/zootaxa.4216.1.5.

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Eigenmannia correntes, a new species belonging to the Eigenmannia trilineata species-group, is described from tributaries of rio Correntes, a major affluent of the rio Piquiri system, upper rio Paraguai basin (Mato Grosso and Mato Grosso do Sul states, Brazil). Eigenmannia correntes is included in the currently poorly defined sternopygid genus Eigenmannia (Ostariophysi: Gymnotiformes) by presenting characters that are either primitive or of uncertain polarity, such as eyes covered by skin, scales present over entire postcranial portion of body, teeth absent from oral valve, infraorbital bones 1+2 with enlarged posterodorsal expansion, and gill rakers short and unossified. The new species is distinguished from all congeners, except those species included in the Eigenmannia trilineata species-group, by the presence of a conspicuous superior midlateral stripe (synapomorphy of this clade). Eigenmannia correntes can be differentiated from all members of the Eigenmannia trilineata species-group, except E. vicentespelaea, E. waiwai and E. besouro, by its subterminal mouth (vs. terminal in remaining species of that group). Further, it differs from these aforementioned species by a number of meristic and morphometric characters, including number of premaxillary and dentary teeth, number of longitudinal series of scales above lateral line, number of pectoral-fin and anal-fin rays, eye diameter, postorbital distance, and snout length. Finally, notes on reproduction and parasitism for E. correntes are presented.

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3

KRAMER, BERND, and BRUNHILDE OTTO. "Waveform Discrimination in the Electric Fish Eigenmannia: Sensitivity for the Phase Differences Between the Spectral Components of a Stimulus Wave." Journal of Experimental Biology 159, no. 1 (September 1, 1991): 1–22. http://dx.doi.org/10.1242/jeb.159.1.1.

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Eigenmannia lineata is a tropical South American gymnotiform fish that is both electrogenic and electroreceptive. Its electric organ generates a constant-frequency wave discharge (EOD) that is sexually dimorphic in waveform and harmonic content. Eigenmannia discriminates digitally synthesized, natural male and female EOD waveforms of identical frequency and amplitude. Experiments were devised to investigate behaviourally the sensory mechanism of this discrimination. Both the content in higher harmonics (as seen in an amplitude spectrum) and the waveform (phase spectrum) could provide the cues Eigenmannia uses for discrimination. Five Eigenmannia were trained to discriminate artificially generated stimuli composed of the fundamental frequency, f1, and its harmonic, f2, of a frequency twice that of f1 and of weaker intensity (−13 to −3dB re f1; a similar variation is found among the EODs of different Eigenmannia individuals). The rewarded stimulus, S+ (with a strong f2 intensity of −3dB re f1), remained constant throughout the experiments. The family of negative (S-) stimuli all had a phase difference of 0°, that is, no phase difference, between their harmonics, while the S+ stimulus had a phase difference of 90°. Therefore, all S- stimuli differed from the S+ stimulus in waveform, while one S- stimulus had an amplitude spectrum identical to that of the S+ stimulus. All fish discriminated any S- signal tested from the S+ stimulus, including the S- stimulus with an identical amplitude spectrum, both when the test signals had identical energy contents (that is, slightly different peak-to-peak amplitudes) and when they had identical peak-to-peak amplitudes (hence, slightly different energy contents). These results arc evidence for a true waveform (time domain) sensitivity of Eigenmannia. A sensory mechanism is proposed that enables Eigenmannia to assess the P/N ratio of a wave signal, that is, the duration ratio of positive (P) and negative (N) half-waves between zero-crossings of a stimulus cycle (the S+ and all S- stimuli, as well as female and male EODs, differ in this regard).

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4

Bichuette, Maria Elina, and Eleonora Trajano. "Morphology and distribution of the cave knifefish Eigenmannia vicentespelaea Triques, 1996 (Gymnotiformes: Sternopygidae) from Central Brazil, with an expanded diagnosis and comments on subterranean evolution." Neotropical Ichthyology 4, no. 1 (March 2006): 99–105. http://dx.doi.org/10.1590/s1679-62252006000100011.

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We present herein data on morphology and distribution of the cave knifefish Eigenmannia vicentespelaea Triques, 1996, from the São Domingos karst area, Central Brazil, comparing it to the epigean (surface) species, Eigenmannia sp., found in the same area (but not syntopic with E. vicentespelaea) and also with congeners from other localities. Collecting sites comprising epigean and subterranean stream reaches in São Domingos were sampled during the dry seasons of 1999, 2000, and 2001 using several methods. Preserved specimens of E. vicentespelaea (n=25, including holotype and paratype) and of Eigenmannia sp. (n=15) were compared with focus on morphometric characters, body pigmentation and eye condition. A combination of characters separates E. vicentespelaea from Eigenmannia sp. and other congeners: the length from the tip of the snout to the posterior of the anal fin base, ocular diameter: head length and pre-anal distance: head length proportions, and body pigmentation. A wider morphometric variation in E. vicentespelaea is described than that reported in the original description (based on two specimens).

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5

Sindeaux Neto, José Ledamir, Michele Velasco, José Mauro Vianna da Silva, Patricia de Fátima Saco dos Santos, Osimar Sanches, Patricia Matos, and Edilson Matos. "Lymphocytic meningoencephalomyelitis associated with Myxobolus sp. (Bivalvulidae: Myxozoa) infection in the Amazonian fish Eigenmannia sp. (Sternopygidae: Gymnotiformes)." Revista Brasileira de Parasitologia Veterinária 25, no. 2 (April 12, 2016): 158–62. http://dx.doi.org/10.1590/s1984-29612016023.

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Abstract The genus Myxobolus, parasites that infect fishes, which cause myxobolosis, includes spore organisms belonging to the phylum Myxozoa and represents approximately 36% of all species described for the entire phylum. This study describes lymphocytic meningoencephalomyelitis associated with Myxobolus sp. infection in the brain and spinal cord (the central nervous system, CNS) of Eigenmannia sp., from the Amazon estuary region, in the Administrative District of Outeiro (DAOUT), Belém, Pará, Brazil. In May and June 2015, 40 Eigenmannia sp. specimens were captured from this region and examined. The fish were anesthetized, slaughtered and dissected for sexing (gonad evaluation) and studying parasites and cysts; after diagnosing the presence of the myxozoans using a light microscope, small fragments of the brain and spinal cord were removed for histological processing and Hematoxylin-Eosin and Ziehl-Neelsen staining. Histopathological analysis of the brain and spinal cord, based on histological sections stained with Hematoxylin-Eosin, pronounced and diffuse edema in these tissues, and congestion, degeneration, and focal necrosis of the cerebral cortex. The present study describes lymphocytic meningoencephalomyelitis associated with infection by Myxobolus sp. in the central nervous system of Eigenmannia sp.

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6

Lin, Ruizhe, Jia Ge, Phiet Tran, Luis Alberto Perea, Ryan Toole, and Mable P. Fok. "Biomimetic photonics: jamming avoidance system in Eigenmannia." Optics Express 26, no. 10 (May 9, 2018): 13349. http://dx.doi.org/10.1364/oe.26.013349.

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7

KAWASAKI, MASASHI. "Temporal Hyperacuity in the Gymnotiform Electric Fish,Eigenmannia." American Zoologist 33, no. 1 (February 1993): 86–93. http://dx.doi.org/10.1093/icb/33.1.86.

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8

Silva, Danillo S., Susana SR Milhomem, Julio C. Pieczarka, and Cleusa Y. Nagamachi. "Cytogenetic studies in Eigenmannia virescens (Sternopygidae, Gymnotiformes) and new inferences on the origin of sex chromosomes in the Eigenmannia genus." BMC Genetics 10, no. 1 (2009): 74. http://dx.doi.org/10.1186/1471-2156-10-74.

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9

de Sene, Viviani F., José C. Pansonato-Alves, Daniela C. Ferreira, Ricardo Utsunomia, Claudio Oliveira, and Fausto Foresti. "Mapping of the Retrotransposable Elements Rex1 and Rex3 in Chromosomes of Eigenmannia (Teleostei, Gymnotiformes, Sternopygidae)." Cytogenetic and Genome Research 146, no. 4 (2015): 319–24. http://dx.doi.org/10.1159/000441465.

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Transposable elements constitute a remarkable fraction of the eukaryote genome and show particular capacity to move and insert in specific regions of the genome. This study identified the retrotransposable elements Rex1 and Rex3 in the genomes of 6 cytotypes of Eigenmannia. The sequences were isolated by PCR, sequenced and physically mapped in the chromosomes of these cytotypes, aiming to investigate the organization and distribution of these elements in this fish group, mainly in the sex chromosomes. The FISH physical mapping revealed that both Rex1 and Rex3 elements are dispersed in small clusters throughout the chromosomes of all cytotypes analyzed. However, conspicuous blocks occur in several samples, including an accentuated accumulation of the Rex3 element in X1 and X2 chromosomes of Eigenmannia sp. 2 and in the X chromosome of E. virescens. The accumulations are coincident with heterochromatin-rich regions, suggesting that Rex3 played a role in the differentiation process of the sex chromosomes.

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10

Takizawa, Y., G. J. Rose, and M. Kawasaki. "Resolving competing theories for control of the jamming avoidance response: the role of amplitude modulations in electric organ discharge decelerations." Journal of Experimental Biology 202, no. 10 (May 15, 1999): 1377–86. http://dx.doi.org/10.1242/jeb.202.10.1377.

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The algorithm for the control of the jamming avoidance response (JAR) of Eigenmannia has been the subject of debate for over two decades. Two competing theories have been proposed to explain how fish determine the correct direction to shift their pacemaker frequency during jamming. One theory emphasizes the role of time-asymmetric beat envelopes, while the other emphasizes the role of amplitude- and phase-difference computations that arise from the differences in spatial geometry of the electric fields of neighboring fish. In repeating earlier experiments, we found that the decision to raise or lower the pacemaker frequency reliably above or below its resting level depends on the latter process, and that frequency deceleration responses to amplitude modulation appear to be sufficient to explain previous experimental results on which the former theory is based. Specifically, fish of the genus Eigenmannia show differential deceleration responses to asymmetric beat envelopes. The deceleration responses do not require phase modulation and show a sensitivity for amplitude modulation depth and selectivity for amplitude modulation rate comparable with that of JARs that are elicited when amplitude- and phase-difference information is available.

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11

Assad, C., B. Rasnow, P. K. Stoddard, and J. M. Bower. "The electric organ discharges of the gymnotiform fishes: II. Eigenmannia." Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology 183, no. 4 (October 27, 1998): 419–32. http://dx.doi.org/10.1007/s003590050268.

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12

Stöckl, Anna, Fabian Sinz, Jan Benda, and Jan Grewe. "Encoding of social signals in all three electrosensory pathways of Eigenmannia virescens." Journal of Neurophysiology 112, no. 9 (November 1, 2014): 2076–91. http://dx.doi.org/10.1152/jn.00116.2014.

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Extracting complementary features in parallel pathways is a widely used strategy for a robust representation of sensory signals. Weakly electric fish offer the rare opportunity to study complementary encoding of social signals in all of its electrosensory pathways. Electrosensory information is conveyed in three parallel pathways: two receptor types of the tuberous (active) system and one receptor type of the ampullary (passive) system. Modulations of the fish's own electric field are sensed by these receptors and used in navigation, prey detection, and communication. We studied the neuronal representation of electric communication signals (called chirps) in the ampullary and the two tuberous pathways of Eigenmannia virescens. We first characterized different kinds of chirps observed in behavioral experiments. Since Eigenmannia chirps simultaneously drive all three types of receptors, we studied their responses in in vivo electrophysiological recordings. Our results demonstrate that different electroreceptor types encode different aspects of the stimuli and each appears best suited to convey information about a certain chirp type. A decoding analysis of single neurons and small populations shows that this specialization leads to a complementary representation of information in the tuberous and ampullary receptors. This suggests that a potential readout mechanism should combine information provided by the parallel processing streams to improve chirp detectability.

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13

WALTZ, BRANDON T., and JAMES S. ALBERT. "New species of glass knifefish Eigenmannia loretana (Gymnotiformes: Sternopygidae) from the Western Amazon." Zootaxa 4399, no. 3 (March 21, 2018): 399. http://dx.doi.org/10.11646/zootaxa.4399.3.9.

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A new species of the Eigenmannia trilineata species group is described from the Loreto, Peru region of the western Amazon basin. The new species is similar in external appearance to members of the E. trilineata species group, but has a distinct phenotype, being diagnosed from congeners by the following unique combination of characters: four longitudinal dark pigment stipes on the lateral surfaces (over the lateral line, hypaxial muscles, proximal and distal pterygiophore margins); short, relatively round head (head depth 86.8–96.7% head length) with a terminal mouth; intermediate posterodorsal expansion of infraorbital bones 1+2 (60–75% length of infraorbitals 1+2); 11–15 teeth in three rows on the premaxilla; six to seven teeth in a single row on the endopterygoid; eye high on head (suborbital depth 28–36% head length); ii, 13–14 pectoral-fin rays; 183–219 anal-fin rays; and a uniformly dark brown head and pectoral fins on freshly-preserved specimens. The new species extends the geographic range of described species of the E. trilineata species group to the Western Amazon. This new species elevates the current number of valid species within the E. trilineata species group to 15, and the number of species within Eigenmannia to 20.

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14

Campos, Wallacy Adriano Cavalcante, Thaynara Sofia Gomes Vieira, and Kedma Cristine Yamamoto. "Dieta de sarapós da família sternopygidae em ambientes de praia no Rio Negro, Amazonas." Revista Ibero-Americana de Ciências Ambientais 12, no. 2 (January 20, 2021): 482–92. http://dx.doi.org/10.6008/cbpc2179-6858.2021.002.0041.

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Os ambientes de praia na Amazônia Central ocorrem de forma aparente nas margens de rios, paranás e lagos, através da alternância do nível da água, que ocorre a partir do ciclo hidrológico, surgindo durante a fase estacional terrestre mais conhecida como os períodos de vazante e seca. Estes habitats proporcionam abrigo e fonte de alimentação para uma diversa e abundante ictiofauna, dentre as espécies de peixes que habitam os ambientes de praias destacam-se os peixes da ordem Gymnotiformes, os quais são conhecidos popularmente como sarapós ou peixes elétricos, sendo este último, devido a capacidade de gerar uma corrente de carga elétrica para eletrolocação e interações sociais, principalmente para a família Sternopygidae, utilizada na presente pesquisa. Estudos acerca dos hábitos alimentares e dieta dos Gymnotiformes são escassos e, essa falta de conhecimento tanto pela história de vida, comportamento e ecologia são os principais pontos para o não entendimento das pesquisas realizadas, sendo assim, este estudo é primordial para a melhor compreensão dos hábitos alimentares das espécies Eigenmannia macrops, Eigenmannia trilineata e Eigenmannia virescens coletadas em praias do rio Negro. Foram analisados ao total 180 estômagos, 60 de cada espécie e todos apresentaram algum item alimentar, estando os estômagos parcialmente cheios (0-25%) até mesmo distendidos (75-100%) como se destacou para os espécimes de E. macrops. O item alimentar mais frequente foi o de inseto, seguido por material indefinido (digerido) e por fim o item material vegetal. A partir do IAi (%) pode-se classificar as espécies E. macrops (>70%) e E. virescens (>70%) na guilda trófica como insetívoras e E. trilineata como onívora com tendência a insetivoria. O valor calculado para amplitude de nicho trófico apresentou nível intermediário para E. trilineata e E. virescens e baixa para E. macrops, portanto tendo a maior dissimilaridade quanto aos itens consumidos. Quanto ao fator de condição, a espécie E. macrops demonstrou que estava em boas condições de bem-estar mesmo em período de seca, já as espécies E. trilineata e E. virescens apresentaram valores abaixo de zero, o que não as impossibilitou de explorar os recursos alimentares.

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15

Ramcharitar, J. U., E. W. Tan, and E. S. Fortune. "Global Electrosensory Oscillations Enhance Directional Responses of Midbrain Neurons in Eigenmannia." Journal of Neurophysiology 96, no. 5 (November 2006): 2319–26. http://dx.doi.org/10.1152/jn.00311.2006.

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Eigenmannia, a genus of weakly electric fish, exhibits a specialized behavior known as the jamming avoidance response (JAR). The JAR results in a categorical difference between Eigenmannia that are in groups of conspecifics and those that are alone. Fish in groups exhibit the JAR behavior and thereby experience ongoing, global synchronous 20- to 50-Hz electrosensory oscillations, whereas solitary fish do not. Although previous work has shown that these ongoing signals do not significantly degrade electrosensory behavior, these oscillations nevertheless elicit short-term synaptic depression in midbrain circuits. Because short-term synaptic depression can have profound effects on the transmission of information through synapses, we examined the differences in intracellularly recorded responses of midbrain neurons in awake, behaving fish to moving electrosensory images under electrosensory conditions that mimic solitary fish and fish in groups. In solitary conditions, moving objects elicited Gaussian or sinusoidal postsynaptic potentials (PSPs) that commonly exhibited preferential responses to a direction of motion. Surprisingly, when the same stimulus was presented in the presence of the global oscillations, directional selectivity was increased in all neurons tested. The magnitudes of the differences in PSP amplitude for preferred and nonpreferred directions were correlated with a measure of short-term synaptic depression in both conditions. The electrosensory consequences of the JAR appear to result in an enhancement of the representation of direction of motion in midbrain neurons. The data also support a role for short-term synaptic depression in the generation and modulation of directional responses.

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16

Lundberg, John G., and J. Curt Stager. "Microgeographic diversity in the neotropical knife-fish Eigenmannia macrops (Gymnotiformes, Sternopygidae)." Environmental Biology of Fishes 13, no. 3 (July 1985): 173–81. http://dx.doi.org/10.1007/bf00000928.

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17

KRAMER, BERND. "Jamming Avoidance in the Electric Fish Eigenmannia: Harmonic Analysis of Sexually Dimorphic Waves." Journal of Experimental Biology 119, no. 1 (November 1, 1985): 41–69. http://dx.doi.org/10.1242/jeb.119.1.41.

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1. The present report shows an intraspecific, sexually dimorphic variation in harmonic content and waveform, as well as intensity, of the Electric Organ Discharges (EODs) in the green knife fish, Eigenmannia (Figs 2, 11). There is a close correlation between harmonic content of the EODs and waveform (as defined by the ratio of intervals between zero-crossings in the two half-waves of one EOD cycle; Fig. 3). The aim of the following experiments was to determine whether the fish are sensitive to differences in stimulus waveform or harmonic content. 2. Stimulation with electric fields of various waveforms but equal peak-to-peak amplitudes at frequencies close to the fish's frequency elicited the Jamming Avoidance Response (JAR) which is an EOD frequency change increasing the frequency difference (Watanabe & Takeda, 1963). The strength of JARs to distorted square wave and sawtooth stimuli was 25% smaller than that elicited by sine wave stimuli (Fig. 6). Undistorted square waves elicited stronger responses than sine waves, while undistorted sawtooth waves were the least effective (Table 1). The differences in response strength were proportional to differences in the intensity of the fundamental frequency or first harmonic, f1, of the stimulus waveforms. 3. Subharmonic stimuli of nine artificial or synthesized natural waveforms at frequencies near one-half or one-third of the EOD resting frequency elicited responses only when a strong higher harmonic, or overtone, of the stimulus was close to the EOD fundamental frequency (Fig. 7). Stimuli of different waveforms, but identical spectral amplitudes, elicited similar responses not significantly different from each other, at stimulus frequencies near one-half (Table 3) and near the EOD resting frequency (Fig. 10). 4. Eigenmannia's JARs to synthesized male EODs at frequencies close to the fish's frequency were weaker than those to female EODs of equal peak-to-peak amplitude. The weaker response was proportional to the weaker intensity of the first harmonic of the male EOD (Fig. 12). A stimulus frequency near one-half of the EOD baseline frequency evoked opposite results, as the second harmonic, f2, of the male EOD was relatively four times stronger than that of the female EOD (Table 4).

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18

KRAMER, BERND, and IVO KAUNZINGER. "Electrosensory Frequency and Intensity Discrimination in the Wave-Type Electric Fish Eigenmannia." Journal of Experimental Biology 161, no. 1 (November 1, 1991): 43–59. http://dx.doi.org/10.1242/jeb.161.1.43.

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Eigenmannia's frequency and intensity discrimination thresholds were determined for a range of seven frequencies (50–1700Hz), centered on a fish's individual discharge frequency, using a conditioned go/no-go paradigm. The threshold criterion was ‘50% correct choices’ (of the rewarded stimulus, S+, over the unrewarded stimulus, S-); this was validated by testing for statistically significantly shorter response latencies for the S+ compared with the S- stimulus. The stimuli consisted of sine wave bursts presented for up to 20 s, repeated at 2 s−1 (rise and fall times of an individual burst, 50 ms; holding time, 250 ms; silence, 150ms). When testing for frequency discrimination, the sine wave bursts alternated in frequency (λf); for intensity discrimination, every other sine wave burst was of increased intensity (λI). The reference stimulus intensity was 30 dB with reference to a fish's individual absolute threshold for a continuous sine wave at that frequency, previously determined using a conditioned go response. Sensory discrimination was best close to a fish's individual discharge frequency. At 30 dB sensation level, fish discriminated frequency differences as small as 0.52 Hz (0.60 and 0.79 Hz in two other individuals) and intensity differences as small as 0.56dB (1 dB in two other fish). At stimulus frequencies different from a fish's discharge frequency, Eigenmannia's frequency discrimination declined at lower frequencies at a rate of up to 1 Hz octave−1, and at higher frequencies at a rate of up to 3 Hz octave−1. For Eigenmannia's intensity discrimination a similar loss was observed: at frequencies lower than a fish's discharge frequency, intensity discrimination thresholds rose at a rate of less than 1 dB octave−1, while the rate was below 2 dB octave−1 for higher frequencies. Compared with other acoustico-lateral senses in lower vertebrates, Eigenmannia's electrosensory frequency and intensity discrimination is unusually high, in the range of that known for audition in the most sensitive higher vertebrates with a cochlea (for example, human). This emphasizes Eigenmannia's specialized ‘active’ electrosensory system, which detects the presence of a stimulus field as the modulation of a fish's own ‘carrier’ signal in amplitude and phase (beat analysis), as opposed to ‘passive’ sensory systems, which must deal with unpredictable signals from the environment as they occur.

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19

DUTRA, GUILHERME MOREIRA, LUIZ ANTÔNIO WANDERLEY PEIXOTO, CARLOS DAVID DE SANTANA, and WOLMAR BENJAMIN WOSIACKI. "A new species of Eigenmannia Jordan & Evermann (Teleostei: Gymnotiformes: Sternopygidae) from Río Ventuari, Venezuela." Zootaxa 4422, no. 1 (May 22, 2018): 132. http://dx.doi.org/10.11646/zootaxa.4422.1.8.

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A new species of Eigenmannia is described from the Río Ventuari, Río Orinoco basin, Venezuela. It is distinguished from congeners by the presence of a bony dorsolateral flange on the dentary, the presence of teeth attached along a bony dorsolateral flange, and by the first premaxillary teeth attached to the anteroventral margin of the premaxilla. It is further distinguished from all remain congeners by a combination of characters, including a subterminal mouth, 99–107 scales along the lateral line until the end of the anal fin, and ii, 16–17 pectoral-fin rays.

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20

Sene, Viviane França, José Carlos Pansonato-Alves, Ricardo Utsunomia, Claudio Oliveira, and Fausto Foresti. "Karyotype diversity and patterns of chromosomal evolution in Eigenmannia (Teleostei, Gymnotiformes, Sternopygidae)." Comparative Cytogenetics 8, no. 4 (November 17, 2014): 301–11. http://dx.doi.org/10.3897/compcytogen.v8i4.8396.

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21

Fujita, Daichi, Tetsuya Asai, and Yoshihito Amemiya. "A neuromorphic MOS circuit imitating jamming avoidance response of Eigenmannia." Nonlinear Theory and Its Applications, IEICE 2, no. 2 (2011): 205–17. http://dx.doi.org/10.1587/nolta.2.205.

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22

von der Emde, G. "Capacitance detection in the wave-type electric fish Eigenmannia during active electrolocation." Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology 182, no. 2 (January 13, 1998): 217–24. http://dx.doi.org/10.1007/s003590050172.

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23

MOYSES, C. B., S. MOCKFORD, L. F. ALMEIDA-TOLEDO, and J. M. WRIGHT. "Nine polymorphic microsatellite loci in the Neotropical electric eel Eigenmannia (Teleostei: Gymnotiformes)." Molecular Ecology Notes 5, no. 1 (March 2005): 7–9. http://dx.doi.org/10.1111/j.1471-8286.2004.00803.x.

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24

Vischer, Heinrich A. "The Development of Lateral-Line Receptors in Eigenmannia (Teleostei, Gymnotiformes)." Brain, Behavior and Evolution 33, no. 4 (1989): 205–22. http://dx.doi.org/10.1159/000115929.

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Vischer, Heinrich A. "The Development of Lateral-Line Receptors in Eigenmannia (Teleostei, Gymnotiformes)." Brain, Behavior and Evolution 33, no. 4 (1989): 223–36. http://dx.doi.org/10.1159/000115930.

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26

Wong, Calvin J. H. "Connections of the basal forebrain of the weakly electric fish,Eigenmannia virescens." Journal of Comparative Neurology 389, no. 1 (December 8, 1997): 49–64. http://dx.doi.org/10.1002/(sici)1096-9861(19971208)389:1<49::aid-cne4>3.0.co;2-e.

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27

Rose, G. J., and E. S. Fortune. "Mechanisms for generating temporal filters in the electrosensory system." Journal of Experimental Biology 202, no. 10 (May 15, 1999): 1281–89. http://dx.doi.org/10.1242/jeb.202.10.1281.

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Temporal patterns of sensory information are important cues in behaviors ranging from spatial analyses to communication. Neural representations of the temporal structure of sensory signals include fluctuations in the discharge rate of neurons over time (peripheral nervous system) and the differential level of activity in neurons tuned to particular temporal features (temporal filters in the central nervous system). This paper presents our current understanding of the mechanisms responsible for the transformations between these representations in electric fish of the genus Eigenmannia. The roles of passive and active membrane properties of neurons, and frequency-dependent gain-control mechanisms are discussed.

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28

Bücker, Augusto, Wanderson Carvalho, and José Antonio Alves-Gomes. "Avaliação da mutagênese e genotoxicidade em Eigenmannia virescens (Teleostei: Gymnotiformes) expostos ao benzeno." Acta Amazonica 36, no. 3 (2006): 357–64. http://dx.doi.org/10.1590/s0044-59672006000300011.

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Os efeitos de substâncias genotóxicas sobre o genoma de peixes tem sido objeto de muitos estudos, sobretudo daqueles que buscam estabelecer a resposta dos genes aos estímulos ambientais. O presente trabalho teve como objetivo realizar um estudo sobre mutagenicidade e genotoxicidade em peixes elétricos da espécie Eingenmannia virescens, pela exposição ao benzeno (50ppm), utilizando as técnicas da Freqüência de Micronúcleos (MNs) e o Ensaio do Cometa. Foram coletadas amostras do sangue de dez peixes em diferentes tempos de exposição: T0, 24h, 48h, 72h, 96h e 360h (15 dias). Para a análise das lâminas no Teste do MN, foram contadas 1.000 células e estipulada a freqüência de ocorrência de MNs. Para análise do Ensaio do Cometa a contagem foi feita estipulando quatro classes de danos: I - II - III - IV, e para a análise estatística foram atribuídos valores numéricos (ranques) de 0 a 3, respectivamente, verificando diferenças significativas para a soma dos ranques em todos os tempos de exposição em relação ao T0. No Teste do Micronúcleo não foi possível detectar efeitos mutagênicos significativos nos eritrócitos analisados. No entanto, para o Ensaio do Cometa os resultados sugerem ação genotóxica do benzeno, devido a um aumento gradual no número de células com maiores classes de danos de acordo com maior tempo de exposição, indicando um efeito tempo-dependente. Estes resultados sugerem maior sensibilidade do Ensaio do Cometa que o Teste do MN.

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29

Mathieson, William B., Walter Heiligenberg, and Leonard Maler. "Ultrastructural studies of physiologically identified electrosensory afferent synapses in the gymnotiform fish,Eigenmannia." Journal of Comparative Neurology 255, no. 4 (January 22, 1987): 526–37. http://dx.doi.org/10.1002/cne.902550405.

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30

Metzner, W. "The jamming avoidance response in Eigenmannia is controlled by two separate motor pathways." Journal of Neuroscience 13, no. 5 (May 1, 1993): 1862–78. http://dx.doi.org/10.1523/jneurosci.13-05-01862.1993.

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31

Roth, E., K. Zhuang, S. A. Stamper, E. S. Fortune, and N. J. Cowan. "Stimulus predictability mediates a switch in locomotor smooth pursuit performance for Eigenmannia virescens." Journal of Experimental Biology 214, no. 7 (March 9, 2011): 1170–80. http://dx.doi.org/10.1242/jeb.048124.

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32

Metzner, Walter, and Svenja Viete. "The neuronal basis of communication and orientation in the weakly electric fish,Eigenmannia." Naturwissenschaften 83, no. 2 (February 1996): 71–77. http://dx.doi.org/10.1007/bf01141873.

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33

Metzner, Walter, and Svenja Viete. "The neuronal basis of communication and orientation in the weakly electric fish,Eigenmannia." Naturwissenschaften 83, no. 1 (January 1996): 6–14. http://dx.doi.org/10.1007/bf01139304.

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34

Moysés, Cinthia Bachir, Maria de Fatima Zambelli Daniel-Silva, Carlos Eduardo Lopes, and Lurdes Foresti de Almeida-Toledo. "Cytotype-specific ISSR profiles and karyotypes in the Neotropical genus Eigenmannia (Teleostei: Gymnotiformes)." Genetica 138, no. 2 (September 25, 2009): 179–89. http://dx.doi.org/10.1007/s10709-009-9407-6.

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35

Ramcharitar, John U., Eric W. Tan, and Eric S. Fortune. "Effects of global electrosensory signals on motion processing in the midbrain of Eigenmannia." Journal of Comparative Physiology A 191, no. 9 (July 6, 2005): 865–72. http://dx.doi.org/10.1007/s00359-005-0008-2.

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36

KRAMER, BERND. "The Sexually Dimorphic Jamming Avoidance Response in the Electric Fish Eigenmannia (Teleostei, Gymnotiformes)." Journal of Experimental Biology 130, no. 1 (July 1, 1987): 39–62. http://dx.doi.org/10.1242/jeb.130.1.39.

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Eigenmannia's jamming avoidance response (JAR) is a frequency change of its electric organ discharge (EOD) in response to an electric stimulus of similar frequency (small ΔF; ΔF = FFish - FStim). It is assumed that the response to an unclamped stimulus, ΔR = FResponce - FRest, is stereotyped and non-habituating, and improves the fish's electrolocation performance in the presence of a jamming stimulus, such as the EOD of a nearby conspecific. Adult females gravid with eggs (N = 3) gave good responses (frequency decrease of at least 3 Hz) to -ΔF (stimulus frequency higher than fish frequency), but no response or only weak responses (<0.5 Hz) to +ΔF (stimulus frequency lower than fish frequency). AFter 2.75 years, a sexually mature female still showed the same behaviour, whereas an immature female (see below) had changed its behaviour considerably on becoming sexually mature. Large males (N = 4) did not give JARs to + ΔF, and no JARs or only weak ones to -ΔF (|ΔR| < 0.7 Hz). Increasing the stimulus intensity by +10 or +20 dB did not change this result. After 2.5 years, two large males were still found to be almost unresponsive. However, large males gave rapid frequency modulations (‘short rises’ and “interruptions'), which have been described from threatening fish likely to attack, even at the weakest stimulus intensity. One group of juveniles (N = 4; probably females) gave only a weak increase in frequency (ΔR < 0.9 Hz) in response to +ΔF but a strong frequency decrease (|ΔR| > 2 Hz) in response to -ΔF. Another group of juveniles (N = 4; probably males) gave strongest responses (ΔR > 3 Hz) to ΔF = 0 Hz. In these juveniles, the ‘equilibrium point’ of no response was at ΔF ≊ −0.6 Hz to −1 Hz instead of at ΔF = 0 Hz. They thus increased, rather than decreased, their EOD frequency even at small -ΔFs, which would have been more economical. A decrease in frequency was weaker than an increase. A significant frequency change could even be elicited by stimuli of ΔF = O Hz that are phase-locked to the EOD. The accuracy of assessment of ΔF, as determined in juvenile fish giving good +ΔRs and -ΔRs, was not better than ±0.3 Hz (at ΔF = −0.6 Hz). The JAR showed strong habituation. None of the 14 fish showed a frequency difference vs response curve close to optimal for the purpose of jamming avoidance. An alternative function of the JAR in social communication is considered.

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37

Giora, Júlia, and John R. Burns. "Sperm ultrastructure in three different families of weakly electric fishes (Teleostei: Gymnotiformes)." Neotropical Ichthyology 9, no. 4 (November 23, 2011): 881–88. http://dx.doi.org/10.1590/s1679-62252011005000047.

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This study presents details of sperm ultrastructure for Gymnotus aff. carapo (Gymnotidae), Eigenmannia trilineata (Sternopygidae), and three Brachyhypopomus species (B. draco, B. bombilla, and B. gauderio - Hypopomidae) from southern Brazil. Differences were found among the representatives of the different families. For example, nuclear rotation was present in E. trilineata and in the Brachyhypopomus species, but absent in Gymnotus aff. carapo, and the presence of flagellar fins was only observed in E. trilineata. Some intraspecific variations could also be noticed among the Brachyhypopomus species analyzed. Most of the characters found in the spermatozoa of the species studied herein are shared with species of Gymnotiformes previously analyzed.

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38

PEIXOTO, LUIZ ANTÔNIO W., and WOLMAR B. WOSIACKI. "Eigenmannia besouro, a new species of the Eigenmannia trilineata species-group (Gymnotiformes: Sternopygidae) from the rio São Francisco basin, northeastern Brazil." Zootaxa 4126, no. 2 (June 17, 2016): 262. http://dx.doi.org/10.11646/zootaxa.4126.2.6.

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39

Giora, Júlia, and Clarice Bernhardt Fialho. "Reproductive biology of weakly electric fish Eigenmannia trilineata López and Castello, 1966 (Teleostei, Sternopygidae)." Brazilian Archives of Biology and Technology 52, no. 3 (June 2009): 617–28. http://dx.doi.org/10.1590/s1516-89132009000300014.

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This study described the reproductive biology of a population of the weakly electric fish Eigenmannia trilineata from southern Brazil, providing the information on the estimation of reproductive period, fecundity, spawning type, first maturation size, and analysis of gonadal morphology and histology of the species, relating these data to alimentary and abiotic characters. The species showed a relatively long reproductive period, a relative fecundity of 0.27 oocytes per mg of total weight and a parcelled spawning type. First maturation size estimated for the females was 80.5 mm and for the males 63.5 mm of total length. Sex ratio did not differ from 1:1 under a X²test (α= 0.01) during all the sampled months. Sexual dimorphism was related to total length, and males had larger total length than females. The abiotic factors photoperiod and water conductivity presented significant correlations with female GSI, while male GSI presented a significant correlation only with photoperiod.

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40

de Almeida-Toledo, L. F., M. F. Z. Daniel-Silva, C. B. Moysés, S. B. A. Fonteles, C. E. Lopes, A. Akama, and F. Foresti. "Chromosome evolution in fish: sex chromosome variability in Eigenmannia virescens (Gymnotiformes: Sternopygidae)." Cytogenetic and Genome Research 99, no. 1-4 (2002): 164–69. http://dx.doi.org/10.1159/000071589.

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41

Toledo, Almeida, E. Viegas-Péquignot, F. Foresti, Toledo Filho, and B. Dutrillaux. "BrdU replication patterns demonstrating chromosome homoeologies in two fish species, genus Eigenmannia." Cytogenetic and Genome Research 48, no. 2 (1988): 117–20. http://dx.doi.org/10.1159/000132603.

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42

Vischer, H. A., M. J. Lannoo, and W. Heiligenberg. "Development of the electrosensory nervous system in eigenmannia (gymnotiformes): I. The peripheral nervous system." Journal of Comparative Neurology 290, no. 1 (December 1, 1989): 16–40. http://dx.doi.org/10.1002/cne.902900103.

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43

De Almeida Toledo, L. F., F. Foresti, and S. De Almeida Toledo Filho. "Spontaneous triploidy and NOR activity in Eigenmannia sp. (Pisces, Sternopygidae) from the Amazon basin." Genetica 66, no. 2 (May 1985): 85–88. http://dx.doi.org/10.1007/bf00139713.

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44

Helligenberg, Walter, and Gary Rose. "Neural correlates of the jamming avoidance response (JAR) in the weakly electric fish Eigenmannia." Trends in Neurosciences 8 (January 1985): 442–49. http://dx.doi.org/10.1016/0166-2236(85)90157-2.

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45

Kawasaki, Masashi, and Walter Heiligenberg. "Individual prepacemaker neurons can modulate the pacemaker cycle of the gymnotiform electric fish,Eigenmannia." Journal of Comparative Physiology A 162, no. 1 (January 1988): 13–21. http://dx.doi.org/10.1007/bf01342699.

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46

Sas, E., and L. Maler. "The optic tectum of gymnotiform teleosts Eigenmannia virescens and Apteronotus leptorhynchus: A golgi study." Neuroscience 18, no. 1 (May 1986): 215–46. http://dx.doi.org/10.1016/0306-4522(86)90190-9.

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47

Heiligenberg, W., and G. J. Rose. "The optic tectum of the gymnotiform electric fish, Eigenmannia: Labeling of physiologically identified cells." Neuroscience 22, no. 1 (July 1987): 331–40. http://dx.doi.org/10.1016/0306-4522(87)90224-7.

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48

Carlson, Bruce A., and Masashi Kawasaki. "Behavioral responses to jamming and ‘phantom’ jamming stimuli in the weakly electric fish Eigenmannia." Journal of Comparative Physiology A 193, no. 9 (July 3, 2007): 927–41. http://dx.doi.org/10.1007/s00359-007-0246-6.

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49

Kramer, B., and B. Otto. "Female discharges are more electrifying: spontaneous preference in the electric fish, Eigenmannia (Gymnotiformes, Teleostei)." Behavioral Ecology and Sociobiology 23, no. 1 (July 1988): 55–60. http://dx.doi.org/10.1007/bf00303059.

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50

Rincón-Sandoval, Melissa, Ricardo Betancur-R, and Javier A. Maldonado-Ocampo. "Mitochondrial genomes of the South American electric knifefishes Eigenmannia humboldtii (Steindachner 1878), Eigenmannia limbata (Schreiner and Miranda Ribeiro 1903), Sternopygus aequilabiatus (Humboldt 1805) and Sternopygus macrurus (Bloch and Schneider 1801), (Gymnotiformes, Sternopygidae)." Mitochondrial DNA Part B 3, no. 2 (May 11, 2018): 572–74. http://dx.doi.org/10.1080/23802359.2018.1469386.

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