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Photograph of head and body of Gymnotus coropinae, MZUSP 75188, from the vicinity of Tefé, Brazil. Scale bars = 10 mm.
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Gymnotus coropinae, a diminutive species of Neotropical electric fish, was originally described by Hoedeman from Surinam. Shortly after its description, G. coropinae was synonymized with a syn- topic congener, G. anguillaris. Here we redescribe G. coropinae as a valid species distinguishable from all congeners by a unique color pattern comprised of...
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Context 1
... Figs. 2-4 illustrate body shape and pigment patterns. Fig. 3 illustrates a preserved specimen from the region of the type locality in Surinam. Fig. 4 illustrates a live specimen from the vicinity of Tefé, Brazil. Nijssen and Isbrücker (1968, fig. 1) also pro- vide a photograph of a specimen from the region of the type locality in Surinam (ZMA 105.904, 125 mm). Morphometric and meristic data presented in Tables 2 and 3. Cephalic sensory canal pore configurations illustrated in Fig. ...
Citations
... Despite several ichthyological expeditions being carried out along the main rivers of the Colombian river and well recorded heptapteridae species in literature (Donascimiento et al., 2017); Pariolius pax was found only in small creeks tributaries of the upper orinoco river basin, while P. maldonadoi was found in small creeks tributaries of the upper orinoco and Negro rivers. here we increase two new species with specific distribution pattern, P. maldonadoi distributed within both basins (Amazon and orinoco) and P. pax restricted to orinoco river as found in the heptapterids Nemuroglanis mariai (Schultz 1944) and 'Chasmocranus' rosae Eigenmann 1922 and other fish groups (Crampton & Albert, 2003;Freeman et al., 2007;Littmann, 2007;Willis et al., 2007;Albert and Carvalho, 2011;reis et al., 2016;Van der Sleen & Albert, 2017). thus, this geographical distribution shows us an interesting headwater capture scenario between the Amazon and orinoco rivers to be investigated in future studies. ...
Pariolius is a heptapterid genus represented by P. armillatus that is distributed along the upper Amazon River basin. A taxonomic integrative revision of Pariolius from Colombian Rivers revealed two new species. Several approaches as morphological, morphometric, meristic, osteology and molecular data were used to distinguish between Pariolius species. The two new species are distinguished from congeners by the caudal-fin shape and numbers of rays, colorations patterns and several morphometric characters. The two new species of Pariolius are restricted to tributaries of the Upper Orinoco and Upper Negro rivers in Colombia.
... These values were normalized in a range that corresponds from 0 (minimum value) to 1 (maximum value; for observed values and their normalizations see Table S2-S4) for analyses, following the methodology synthesized and justified in Ferrer et al. (2014). The range of the observed values for all taxa were acquired directly from specimens analyzed herein, and compiled from the literature in order to apply the largest range known for each count [Archolaemus species : Vari et al. (2012); Distocyclus species : Dutra et al., (2014), Meunier et al., (2014); Eigenmannia species : Peixoto et al. (2015), Peixoto and Wosiacki (2016), Peixoto and Waltz (2017), Campos-da-Paz and Queiroz (2017), Dutra et al. (2017), Dutra et al. (2018); Japigny: Meunier et al. (2011); Rhabdolichops species: Lundberg and Mago-Leccia (1986), Correa et al., (2006); Brachyhypopomus brevirostris: Crampton et al. (2016); Gymnotus coropinae: Crampton and Albert (2003); Sternarchorhamphus muelleri: Campos-da- Paz (1995)]. ...
We advance on the knowledge of Eigenmanniinae by proposing a hypothesis of phylogenetic relationships based on the parsimony analysis of a diverse set of 144 anatomical characters, 12% of them treated as quantitative and 88% treated as qualitative (8% external morphology, 51% osteology, 21% myology, and 8% neuroanatomy). Thirty‐seven of 45 valid species of Eigenmanniinae are examined in the study, including the incertae sedis species “Eigenmannia” goajira. The final tree yields new insights on species relationships, thus, producing a new classification to Eigenmanninae. Our analysis recovered the monophyly of Eigenmanniinae, Archolaemus, Eigenmannia, and Rhabdolichops. Eigenmannia is proposed as monophyletic based on four morphological synapomorphies, one of which exclusive to the genus. Japigny is proposed to be the sister group of all remaining Eigenmanniinae and “E.” goajira to be the sister group of Archolaemus. The hypothesis of monophyly of Distocyclus including D. conirostris and D. guchereauae is rejected. Consequently, D. guchereauae is included in Eigenmannia, and a new genus is established to include “E.” goajira. A taxonomic key to all genera is provided. In addition, this study highlights the critical played by a diverse set of anatomical and quantitative characters without discretization on phylogenetic reconstructions. We advance on the taxonomic knowledge of Eigenmanniinae by examining most of its species richness and building a hypothesis of phylogenetic relationships based on the parsimony analysis of 144 anatomical characters. As result, a new classification was proposed. This study highlights the crucial role that a diverse set of anatomical characters play at different hierarchical levels in phylogenetic reconstructions.
... Albert & Miller (1995) and Albert (2001) recognized three species-groups within Gymnotus based on color pattern and body proportions, the G. anguillaris Hoedeman 1962, G. carapo Linnaeus 1758, and G. cylindricus La Monte 1935 species-groups. Later on, Albert & Crampton (2003) reviewed and summarized the diagnostic characters of the genus and of the three species-groups, renaming the G. anguillaris species-group as G. pantherinus (Steindachner 1908) species-group. The species included in the G. pantherinus group are distinguished from those in the other two species-groups by the possession of a slender body; proximal portion of fifth rib with broad triangular ridge, more than three times width of sixth rib; and dentary hook at mental symphysis composed of paired ventroposteriorly oriented processes (Albert & Crampton 2003). ...
... The new species is referred to Gymnotus by possessing all the diagnostic features proposed by Albert (2001) for the genus, and to the G. pantherinus species-group in possessing all characters proposed by Albert & Crampton (2003) to define the group. The new species cannot be included in any of the other two Gymnotus species-group since G. cylindricus species-group comprises only two species endemic to drainages of Middle America that present reduction in the number of anal fin rays to less than 200, and species of the G. carapo species-group possess a clear or pale patch in the caudal end of the anal fin, characters that are not present in G. refugio. ...
Gymnotus refugio, new species, is described from coastal rivers of Rio Grande do Sul and Santa Catarina states, Brazil. It is diagnosed from most species of the Gymnotus pantherinus species-group by the coloration pattern, further differing from G. pantherinus and G. capitimaculatus on the basis of morphometric and meristic characters. The new species represents the most meridional record of the G. pantherinus species-group.
... Pulse waveforms vary between different individuals, thus a single restrained fish was used to ensure that the pulse waveforms varied only as a function of the source-detector geometry. It was not possible to determine exactly the species of our fish due to nearly indistinguishable external appearances and pulse waveforms of numerous Gymnotus species (Crampton et al. 2003;Crampton and Albert 2003;Rodríguez-Cattaneo et al. 2008). The sex could not be determined by external appearance alone, and a dissection was not performed. ...
... Pulse waveforms vary between different individuals, thus a single restrained fish was used to ensure that the pulse waveforms varied only as a function of the source-detector geometry. It was not possible to determine exactly the species of our fish due to nearly indistinguishable external appearances and pulse waveforms of numerous Gymnotus species (Crampton et al. 2003;Crampton and Albert 2003;Rodríguez-Cattaneo et al. 2008). The sex could not be determined by external appearance alone, and a dissection was not performed. ...
Physiological measurements from an unrestrained, untethered, and freely moving animal permit analyses of neural states correlated to naturalistic behaviors of interest. Precise and reliable remote measurements remain technically challenging due to animal movement, which perturbs the relative geometries between the animal and sensors. Pulse-type electric fish generate a train of discrete and stereotyped electric organ discharges (EOD) to sense their surroundings actively, and rapid modulation of the discharge rate occurs while free swimming in Gymnotus sp. The modulation of EOD rates is a useful indicator of the fish's central state such as resting, alertness, and learning associated with exploration. However, the EOD pulse waveforms remotely observed at a pair of dipole electrodes continuously vary as the fish swims relative to the electrodes, which biases the judgment of the actual pulse timing. To measure the EOD pulse timing more accurately, reliably, and noninvasively from a free-swimming fish, we propose a novel method based on the principles of waveform reshaping and spatial averaging. Our method is implemented using envelope extraction and multichannel summation, which is more precise and reliable compared with other widely used threshold- or peak-based methods according to the tests performed under various source-detector geometries. Using the same method, we constructed a real-time electronic pulse detector performing an additional online pulse discrimination routine to enhance further the detection reliability. Our stand-alone pulse detector performed with high temporal precision (<10 μs) and reliability (error <1 per 10(6) pulses) and permits longer recording duration by storing only event time stamps (4 bytes/pulse).
... Despite the difficulty of identifying many small-bodied fish species in Amazonian streams (Römer 2000, Crampton & Albert 2003, Crampton et al. 2005, we showed that the alternative approach of using field guides to identify fishes in a well-known long-term study area can minimize the number of fishes killed in ecological studies. In our area, field identification of species of Gymnotus, Apistogramma and young characins was not reliable and, if species level identification of these groups is required, it would be necessary to collect them or to improve the field identification techniques. ...
Collecting freshwater zoological material for research purposes is common and necessary, but its impact on biological communities is often overlooked. We tested the impacts of a conventional ichthyological collection in small forest streams and showed that fish assemblages recover after a few months. We highlight ecological traits and habitat characteristics that might exacerbate the impacts of repeated removal of fish in long-term investigations, and advocate for the use of a capture-release approach whenever possible.
... Until recently, little was known regarding the systematic relationships among the species of Gymnotus. This was largely due to the lack of adequate species descriptions, with many Gymnotus species lumped under the title Gymnotus carapo (Albert et al., 1999; Albert and Crampton, 2003). However, ongoing efforts to describe the knifefish fauna of South America have revealed that Gymnotus species diversity is far greater than previously thought (e.g., Albert et al., 1999; Albert and Crampton, 2001, 2003; Campos-da-Paz , 2002; Crampton et al., 2003, 2005; Maldonado-Ocampo and Albert, 2004; Fernandes et al., 2005; Cognato et al., 2007; Richer-de-Forges et al., 2009). ...
... This was largely due to the lack of adequate species descriptions, with many Gymnotus species lumped under the title Gymnotus carapo (Albert et al., 1999; Albert and Crampton, 2003). However, ongoing efforts to describe the knifefish fauna of South America have revealed that Gymnotus species diversity is far greater than previously thought (e.g., Albert et al., 1999; Albert and Crampton, 2001, 2003; Campos-da-Paz , 2002; Crampton et al., 2003, 2005; Maldonado-Ocampo and Albert, 2004; Fernandes et al., 2005; Cognato et al., 2007; Richer-de-Forges et al., 2009). Currently 34 valid species of Gymnotus are recognized, and several more morphologically distinct species taxa await formal description. ...
... In both studies, a sister group relationship between Gymnotus and Electrophorus was well supported, indicating the monophyly of the family Gymnotidae (Ellis, 1913; Triques, 1993; Gayet et al., 1994; Alves-Gomes et al., 1995; Albert and Campos-da-Paz, 1998; Albert, 2001; Albert et al., 2004; Albert and Crampton, 2005). Within Gymnotus, three species groups have been proposed based on color pattern, body proportion, and arrangement of laterosensory canals (Fig. 1; Albert and Miller, 1995; Albert, 2001; Albert and Crampton, 2003). These include the G. carapo group (16 species), the G. pantherinus group (13 species), and the Central American G. cylindricus group (two species). ...
The Neotropical knifefish genus Gymnotus is the most broadly distributed and the most diverse (34+species) gymnotiform genus. Its wide range includes both Central and South American drainages, including the Amazon, Orinoco, and La Plata Basins. Like all gymnotiforms, Gymnotus species produce weak electric fields for both navigation and communication, and these fields exhibit interspecific variation in electric waveform characteristics. Both biogeography and electric signal evolution can profitably be analyzed in a phylogenetic context. Here, we present a total evidence phylogeny for 19 Gymnotus species based on data from the mitochondrial cytochrome b and 16S genes (1558 bp), the nuclear RAG2 gene (1223 bp), and 113 morphological characters. Our phylogenetic hypothesis resolves five distinct Gymnotus lineages. In a previous morphology-based analysis, the Central American Gymnotus cylindricus lineage was hypothesized as the sister group to all other Gymnotus species. In our analysis, the G. cylindricus lineage is nested within South American species, and molecular age estimates support a relatively recent origin for the clade in Central America. Phylogenetic optimization of electric signal waveforms indicate that the ancestral state in Gymnotus is a multiphasic (4+phases of alternating polarity) condition, and independent phase loss has occurred in multiple lineages. Gymnotus is a model group for understanding Neotropical diversification and the evolution of communication at a continental scale.
... This article deals with the EO and EOD of Gymnotus coropinae (Hoedeman, 1962;Crampton and Albert, 2003). We described the pattern of electromotive force, the EOD-associated electric field and the anatomical organization of the electrogenic tissue. ...
This article deals with the electric organ and its discharge in Gymnotus coropinae, a representative species of one of the three main clades of the genus. Three regions with bilateral symmetry are described: (1) subopercular (medial and lateral columns of complex shaped electrocytes); (2) abdominal (medial and lateral columns of cuboidal and fusiform electrocytes); and (3) main [four columns, one dorso-lateral (containing fusiform electrocytes) and three medial (containing cuboidal electrocytes)]. Subopercular electrocytes are all caudally innervated whereas two of the medial subopercular ones are also rostrally innervated. Fusiform electrocytes are medially innervated at the abdominal portion, and at their rostral and caudal poles at the main portion. Cuboidal electrocytes are always caudally innervated. The subopercular portion generates a slow head-negative wave (V(1r)) followed by a head-positive spike (V(3r)). The abdominal and main portions generate a fast tetra-phasic complex (V(2345ct)). Since subopercular components prevail in the near field and the rest in the far field, time coincidence of V(3r) with V(2) leads to different waveforms depending on the position of the receiver. This confirms the splitting hypothesis of communication and exploration channels based on the different timing, frequency band and reach of the regional waveforms. The following hypothesis is compatible with the observed anatomo-functional organization: V(1r) corresponds to the rostral activation of medial subopercular electrocytes and V(3r) to the caudal activation of all subopercular electrocytes; V(2), and part of V(3ct), corresponds to the successive activation of the rostral and caudal poles of dorso-lateral fusiform electrocytes; and V(345ct) is initiated in the caudal face of cuboidal electrocytes by synaptic activation (V(3ct)) and it is completed (V(45ct)) by the successive activation of rostral and caudal faces by the action currents evoked in the opposite face.
... Nonetheless, other extensively and recently studied species seem to be distributed within both basins (e.g. Crampton & Albert, 2003;Freeman et al., 2007;Littmann, 2007;Willis et al., 2007). Our surveys obtained many species that were widely distributed throughout the region, with conspecifics captured from both clearwater habitats of the Upper Orinoco and Upper Casiquiare and blackwater habitats of the lower Casiquiare and Rio Negro. ...
Aim The aim of this study was to determine whether the Casiquiare River functions as a free dispersal corridor or as a partial barrier (i.e. filter) for the interchange of fish species of the Orinoco and Negro/Amazon basins using species assemblage patterns according to geographical location and environmental features.
Location The Casiquiare, Upper Orinoco and Upper Negro rivers in southern Venezuela, South America.
Methods Our study was based on an analysis of species presence/absence data and environmental information (11 habitat characteristics) collected by the authors and colleagues between the years 1984 and 1999. The data set consisted of 269 sampled sites and 452 fish species (> 50,000 specimens). A wide range of habitat types was included in the samples, and the collection sites were located at various points along the entire length of the Casiquiare main channel, at multiple sites on its tributary streams, as well as at various nearby sites outside the Casiquiare drainage, within the Upper Orinoco and Upper Rio Negro river systems. Most specimens and field data used in this analysis are archived in the Museo de Ciencias Naturales in Guanare, Venezuela. We performed canonical correspondence analysis (CCA) based on species presence/absence using two versions of the data set: one that eliminated sites having < 5 species and species occurring at < 5 sites; and another that eliminated sites having < 10 species and species occurring at < 10 sites. Cluster analysis was performed on sites based on species assemblage similarity, and a separate analysis was performed on species based on CCA loadings.
Results The CCA results for the two versions of the data set were qualitatively the same. The dominant environmental axis contrasted assemblages and sites associated with blackwater vs. clearwater conditions. Longitudinal position on the Casiquiare River was correlated (r2 = 0.33) with CCA axis-1 scores, reflecting clearwater conditions nearer to its origin (bifurcation of the Orinoco) and blackwater conditions nearer to its mouth (junction with the Rio Negro). The second CCA axis was most strongly associated with habitat size and structural complexity. Species associations derived from the unweighted pair-group average clustering method and pair-wise squared Euclidean distances calculated from species loadings on CCA axes 1 and 2 showed seven ecological groupings. Cluster analysis of species assemblages according to watershed revealed a stronger influence of local environmental conditions than of geographical proximity.
Main conclusions Fish assemblage composition is more consistently associated with local environmental conditions than with geographical position within the river drainages. Nonetheless, the results support the hypothesis that the mainstem Casiquiare represents a hydrochemical gradient between clearwaters at its origin and blackwaters at its mouth, and as such appears to function as a semi-permeable barrier (environmental filter) to dispersal and faunal exchanges between the partially vicariant fish faunas of the Upper Orinoco and Upper Negro rivers.
... Gymnotus carapo and G. coropinae were both originally described from Surinam, and here we present electric organ discharge data from populations of these species captured in northern Surinam. Gymnotus coropinae is a widely distributed species, occurring throughout most of the Amazon and Orinoco basins and the Guyanas [58]. It occurs sympatrically with G. carapo throughout much of its range, including in Surinam where the two species were collected in the same habitat at all sampled locations. ...
Understanding fixed motor pattern diversity across related species provides a window for exploring the evolution of their underlying neural mechanisms. The electric organ discharges of weakly electric fishes offer several advantages as paradigmatic models for investigating how a neural decision is transformed into a spatiotemporal pattern of action. Here, we compared the far fields, the near fields and the electromotive force patterns generated by three species of the pulse generating New World gymnotiform genus Gymnotus. We found a common pattern in electromotive force, with the far field and near field diversity determined by variations in amplitude, duration, and the degree of synchronization of the different components of the electric organ discharges. While the rostral regions of the three species generate similar profiles of electromotive force and local fields, most of the species-specific differences are generated in the main body and tail regions of the fish. This causes that the waveform of the field is highly site dependant in all the studied species. These findings support a hypothesis of the relative separation of the electrolocation and communication carriers. The presence of early head negative waves in the rostral region, a species-dependent early positive wave at the caudal region, and the different relationship between the late negative peak and the main positive peak suggest three points of lability in the evolution of the electrogenic system: a) the variously timed neuronal inputs to different groups of electrocytes; b) the appearance of both rostrally and caudally innervated electrocytes, and c) changes in the responsiveness of the electrocyte membrane.
This study presents a survey of small-stream fish species from the Purus-Madeira interfluve, collected in four streams near Humaitá on the highway BR-319. The results reveal a rich and diversified ichthyofauna with 3016 collected individuals distributed in 84 species, six orders, 25 families, and 60 genera. Of all the specimens collected, the Characiformes was the most representative, with eight families, 26 genera, and 42 species, followed Siluriformes, with nine families, 20 genera, and 23 species. In terms of families, Characidae had the highest number of species (25), followed by Loricariidae (9), and Cichlidae (8). Among the 95 captured species,s 11 are the first records for the region, evidencing a high diversity in these environments. Of the 84 species recorded in this study, 15 have not been assessed by the IUCN, while the remaining 62 include 23 listed as Least Concern (LC), three as data deficient (DD), and one as Near Threatened (NT). The southeastern Amazon region still has few fish surveys, especially in the region comprising the Purus-Madeira Interfluve, which highlights the importance of surveys to fill gaps and understand the biodiversity distribution patterns in the region.
