[Ichthyology • 2026] Molecular Phylogenetics and A New Taxonomy of the Neotropical Electric Fishes (Actinopterygii: Otophysi: Gymnotiformes)

 

Representatives of the six gymnotiform families Apteronotidae (A), Sternopygidae (S), Gymnotidae (G), Electrophoridae (E), Hypopomidae (H), and Rhamphichthyidae (R). 

Top to bottom, and left to right, are: Rhamphichthys rostratus (R), Archolaemus janeae (S), Sternarchorhamphus muelleri (A), Eigenmannia magoi (S), Gymnotus carapo (G), Sternarchorhynchus sp. (A), Apteronotus galvisi (A), Orthosternarchus tamandua (A), “Apteronotus” (Genus B) cuchillejo (A), Apteronotus eschmeyeri (A), Apteronotus cf. albifrons (A), Gymnorhamphichthys sp. (R), Sternarchorhynchus marreroi (A), Sternopygus aequilabiatus (S), Adontosternarchus devenanzii (A), Steatogenys duidae (R), Brachyhypopomus occidentalis (H), Hypopomus artedi (H), and Electrophorus multivalvulus (E). 

in Janzen, Sabaj, Crampton et Lovejoy, 2026.

DOI: doi.org/10.1016/j.ympev.2026.108678 

Photos by M. Sabaj.

  

Highlights: 

• New 9 gene molecular tree for 202 species of Neotropical electric knifefishes (order Gymnotiformes)

• A new taxonomy is proposed, based on the most extensive phylogenetic analysis to date.

• Strong phylogenetic support for 6 families, including the Electrophoridae (electric eels)

• Two main groups of species defined by either pulse or wave-type electric signals.

• Two new suborders: Pulseoidei for pulse-type species and Sinusoidei for wave-type species.

Abstract

The order Gymnotiformes—Neotropical electric eels and knifefishes—comprise a distinctive lineage of freshwater fishes characterized by electrogenesis and electroreception. Despite their ecological, evolutionary, and neurobiological significance, phylogenetic relationships within the order remain incompletely resolved. We present the most taxonomically inclusive molecular phylogeny of Gymnotiformes to date, based on two mitochondrial and seven nuclear genes from 202 species representing 31 of 36 extant genera. Maximum likelihood and Bayesian inference analyses provide strong support for a concordant species-level phylogenetic arrangement that we use to propose a revised classification of Gymnotiformes, including new suprageneric names and reassignments of some taxa and species. We found support for six monophyletic families, including Electrophoridae (electric eels). We propose two new suborders corresponding to electric signal type: Pulseoidei (pulse-type) and Sinusoidei (wave-type), an arrangement that does not allow determination of whether a pulse or wave-type signal was ancestral. In Apteronotidae, the subfamilies Sternarchorhamphinae and Apteronotinae are supported; within Apteronotinae, we establish the tribe Steatogenini to include Porotergus, Sternarchella, and close relatives. We resolve the non-monophyly of Apteronotus with generic reassignments. For Sternopygidae, we support the monophyletic subfamilies Sternopyginae and Eigenmanniinae and resolve polyphyly in Rhabdolichops and Eigenmannia via generic reassignments. Within Gymnotus, we support six species groups. We confirm the sister-group relationship between Hypopomidae and Rhamphichthyidae and clarify their internal structure, including support for six species groups within the diverse genus Brachyhypopomus. Our study provides a robust phylogenetic framework for Gymnotiformes and establishes a foundation for future work on systematics, biogeography, trait evolution, and comparative neurobiology.

 

Keywords: Neotropical, Systematics, Electric eel, Knifefish, Electric organ discharges

Sinusoidei subord. nov. changed from “Sinusoidea” of Albert 2001

Pulseoidei subord. nov. changed from “Pulseoidea” of Alda et al. 2018

Representatives of the six gymnotiform families Apteronotidae (A), Sternopygidae (S), Gymnotidae (G), Electrophoridae (E), Hypopomidae (H), and Rhamphichthyidae (R). 

Top to bottom, and left to right, are: Rhamphichthys rostratus (R), Archolaemus janeae (S), Sternarchorhamphus muelleri (A), Eigenmannia magoi (S), Gymnotus carapo (G), Sternarchorhynchus sp. (A), Apteronotus galvisi (A), Orthosternarchus tamandua (A), “Apteronotus” (Genus B) cuchillejo (A), Apteronotus eschmeyeri (A), Apteronotus cf. albifrons (A), Gymnorhamphichthys sp. (R), Sternarchorhynchus marreroi (A), Sternopygus aequilabiatus (S), Adontosternarchus devenanzii (A), Steatogenys duidae (R), Brachyhypopomus occidentalis (H), Hypopomus artedi (H), and Electrophorus multivalvulus (E). 

Photos by M. Sabaj.

  

 

 Francesco H. Janzen, Mark H. Sabaj, William G.R. Crampton, Nathan R. Lovejoy, 2026. Molecular Phylogenetics and A New Taxonomy of the Neotropical Electric Fishes (Actinopterygii: Otophysi: Gymnotiformes). Molecular Phylogenetics and Evolution. In Press, 108678. DOI: doi.org/10.1016/j.ympev.2026.108678 [10 July 2026]

[Ichthyology • 2020] Gymnotus arapiuns & G. aripuana • Two New Species of Gymnotus (Gymnotiformes: Gymnotidae) from Brazil and Historical Biogeography of the Subgenus Lamontianus

Gymnotus arapiuns & Gymnotus aripuana

 Kim, Crampton & Albert, 2020

DOI: 10.1643/CI-19-205

  twitter.com/IchsAndHerps

Abstract

Gymnotus is the most species-rich and geographically widespread genus of gymnotiform electric fishes and has been widely explored to understand mechanisms of diversification in Neotropical freshwater fishes at a continental scale. Within Gymnotus, the subgenus Lamontianus is a phenotypically distinctive clade with an elongate, cylindrical body shape currently known from four valid species (G. anguillaris, G. cataniapo, G. pedanopterus, and G. tiquie) restricted to rivers draining the Guiana Shield. Here we use aspects of body-surface coloration, meristic, morphological, and osteological data, including cranial, laterosensory pore, and postcranial characters, to diagnose two new species of Lamontianus that inhabit the Aripuanã and Arapiuns rivers that drain the Brazilian Shield. We also use geometric morphometric analyses of head shape to separate the new species from one another and other species of Lamontianus. We report biogeographic distributions for all species of Lamontianus and estimate ancestral geographic ranges and range evolution using the parametric biogeographic program BioGeoBEARS. We use the phylogeny of Lamontianus to test alternative hypotheses regarding lineage divergence times, before or after the formation of the modern East-draining Amazon at c. 10 Ma. Our analysis suggests that diversification in Lamontianus occurred primarily by geographic range fragmentation (vicariance) from an ancestral species distributed across the Western Guiana Shield. These results are similar to those of other Gymnotus and gymnotiform clades, where allopatric speciation and secondary contact due to geographic range expansion are commonly observed. This study brings to 46 the number of valid species of the genus Gymnotus, and to six the number of valid species of the subgenus Lamontianus.

Gymnotus arapiuns, new species 

Etymology.—Named for the Arapiuns River, a blackwater river and tributary of the Tapajós River in Pará state, Brazil. Noun in apposition. 

Gymnotus aripuana, new species

Etymology.—Named for the Aripuanã River in Mato Grosso State, Brazil. Noun in apposition. 

Lesley Y. Kim, William G. R. Crampton and James S. Albert. 2020. Two New Species of Gymnotus (Gymnotiformes: Gymnotidae) from Brazil and Historical Biogeography of the Subgenus Lamontianus. Copeia. 108(3); 468-484. DOI: 10.1643/CI-19-205

twitter.com/IchsAndHerps/status/1289242512347914240

 

[Ichthyology • 2019] Electrophorus varii & E. voltai • Unexpected Species Diversity in Electric Eels with A Description of the Strongest Living Bioelectricity Generator

Electrophorus voltai

de Santana, Wosiacki, Crampton, Sabaj, Dillman, Castro e Castro, Bastos and Vari

de Santana, Crampton, Dillman, Frederico, Sabaj, et al., 2019. 

 DOI: 10.1038/s41467-019-11690-z

Abstract

Is there only one electric eel species? For two and a half centuries since its description by Linnaeus, Electrophorus electricus has captivated humankind by its capacity to generate strong electric discharges. Despite the importance of Electrophorus in multiple fields of science, the possibility of additional species-level diversity in the genus, which could also reveal a hidden variety of substances and bioelectrogenic functions, has hitherto not been explored. Here, based on overwhelming patterns of genetic, morphological, and ecological data, we reject the hypothesis of a single species broadly distributed throughout Greater Amazonia. Our analyses readily identify three major lineages that diverged during the Miocene and Pliocene—two of which warrant recognition as new species. For one of the new species, we recorded a discharge of 860 V, well above 650 V previously cited for Electrophorus, making it the strongest living bioelectricity generator.

Map of northern South America showing distributions of sampled records and type localities (indicated by numbers) for three electric eel species: Electrophorus electricus (red dots, 1 = Suriname River, Suriname); Electrophorus voltai (blue dots, 2 = Rio Ipitinga, Brazil); and Electrophorus varii (yellow dots, 3 = Rio Goiapi, Brazil). Bicolor dots (blue/yellow) indicate sympatric co-occurrence of E. voltai and E. varii. The map was created in ArcGIS (https://www.arcgis.com) with images available at Shuttle Radar Topography Mission, Global Multi-resolution Terrain Elevation Data, and HydroSHEDS database.

Systematic biology

Electrophorus Gill, 1864

 Type species: Gymnotus electricus Linnaeus, 1766. 

Electrophorus electricus (Linnaeus, 1766)

Diagnosis: Ten nucleotides in COI (BOL-COIfishF1/R1; 569-bp fragment): G(8), A(50), T(76), T(77), T(107), C(119), C(182), G(272), G(494), A(560). Ventral outline of head U-shaped, widest at terminus of branchial opening (Fig. 2a) and lateral-line pores 88–101 (versus ovoid, widest anterior to branchial opening, Fig. 2b; 112–146 in E. voltai). Distinguished by skull depressed, cleithrum lies between vertebrae 5 and 6 (Fig. 2a), pectoral-fin rays 32–38, and lateral-line pores 88–101 (versus skull deep, cleithrum lies between vertebrae 1 and 2, Fig. 2c, 20–28, and 124–186 in E. varii, respectively).

Fig. 1 Sampling localities and gene trees for the three species of Electrophorus. a Map of northern South America showing distributions of sampled records and type localities (indicated by numbers) for three electric eel species: Electrophorus electricus (red dots, 1 = Suriname River, Suriname); E. voltai (blue dots, 2 = Rio Ipitinga, Brazil); and E. varii (yellow dots, 3 = Rio Goiapi, Brazil). Bicolor dots (blue/yellow) indicate sympatric co-occurrence of E. voltai and E. varii. The map was created in ArcGIS (https://www.arcgis.com) with images available at Shuttle Radar Topography Mission, Global Multi-resolution Terrain Elevation Data, and HydroSHEDS database. b *BEAST2.4 species tree (top cladogram; 94 specimens: 15 E. electricus, 41 E. voltai, 38 E. varii) based on 5 mitochondrial (trees 1–5; 107 specimens: 19 E. electricus, 43 E. voltai, 45 E. varii) and 5 nuclear genes (6–10; 94 specimens). Higher shading densities represent areas where the majority of trees agree in topology and branch lengths (posterior probabilities >0.99), while lower densities represent areas of uncertainty (Supplementary Data 1)

South American rivers are home to at least three different species of electric eels, including a newly identified species capable of generating a greater electrical discharge than any other known animal, according to a new analysis published in the Sept. 10 issue of the journal Nature Communications. One of the two newly discovered electric eel species, Electrophorus varii (shown above), named is after the late Smithsonian ichthyologist Richard Vari and swims through murky, slow-flowing lowland waters.

photo: D. Bastos

Electrophorus varii, sp. nov. de Santana, Wosiacki, Crampton, Sabaj, Dillman, Mendes-Júnior and Castro e Castro

Etymology: In honor of Richard Peter Vari (1949–2016) for his contributions to ichthyology.

Diagnosis: Eleven nucleotides in COI: A(64), A(80), G(146), G(164), T(190), A(251), A(467), C(512), T(517), A(536), and C(569). Pectoral-fin rays 20–28 and lateral-line pores 124–186 (versus 32–38, and 88–101, respectively, in E. electricus). Distinguished by head narrow, Fig. 2a (versus wide, Fig. 2b, in E. voltai; distance between medial margins of contralateral dentaries at transverse through last two ventral pores 2–3 times shorter in E. varii than E. voltai, Fig. 2a, b), skull deep, cleithrum lies between vertebrae 1 and 2, Fig. 2b (versus skull depressed, cleithrum lies between vertebrae 5 and 6, in both E. electricus and E. voltai Fig. 2a, c).

South American rivers are home to at least three different species of electric eels, including a newly identified species capable of generating a greater electrical discharge than any other known animal, according to a new analysis published in the Sept. 10, 2019 issue of the journal Nature Communications. Electrophorus voltai (shown above), one of the two newly discovered electric eel species, primarily lives further south than Electrophorus electricus on the Brazilian Shield, another highland region.Scientists discovered that E. voltai can discharge up to 860 Volts of electricity--significantly more than the previously known 650 Volts generated by E. electricus. This makes the species the strongest known bioelectric generator, and may be an adaptation to the lower conductivity of highland waters.

photo: L. Sousa

Electrophorus voltai, sp. nov. de Santana, Wosiacki, Crampton, Sabaj, Dillman, Castro e Castro, Bastos and Vari

Etymology: In honor of Alessandro Giuseppe Antonio Anastasio Volta (1745–1827).

Diagnosis: Eight nucleotides in COI: A(25), C(29), C(50), C(86), C(140), A(230), A(338), and C(545). Ventral outline of head ovoid, widest anterior to branchial opening (Fig. 2b) and lateral-line pores 112–146 (versus U-shaped, Fig. 2a, 88–101 in E. electricus). Distinguished by skull depressed, cleithrum lies between vertebrae 5 and 6; and head wide (versus skull deep, cleithrum lies between vertebrae 1 and 2, Fig. 2b, and head narrow in E. varii), and distance between medial margins of contralateral dentaries at transverse through last two ventral pores 2–3 times longer in E. voltai than in E. varii, Fig. 2b, c.

C. David de Santana, William G. R. Crampton, Casey B. Dillman, Renata G. Frederico, Mark H. Sabaj, Raphaël Covain, Jonathan Ready, Jansen Zuanon, Renildo R. de Oliveira, Raimundo N. Mendes-Júnior, Douglas A. Bastos, Tulio F. Teixeira, Jan Mol, Willian Ohara, Natália Castro e Castro, Luiz A. Peixoto, Cleusa Nagamachi, Leandro Sousa, Luciano F. A. Montag, Frank Ribeiro, Joseph C. Waddell, Nivaldo M. Piorsky, Richard P. Vari and Wolmar B. Wosiacki. 2019.  Unexpected Species Diversity in Electric Eels with A Description of the Strongest Living Bioelectricity Generator. Nature Communications. 10; 4000. DOI: 10.1038/s41467-019-11690-z

Smithsonian Scientists Triple Number of Known Electric Eel Species https://www.si.edu/newsdesk/releases/smithsonian-scientists-triple-number-known-electric-eel-species via @Smithsonian

  

Electric eels are naked-back knifefishes (Gymnotidae) and are more closely related to catfish and carp than to other eel families.

The study, published in Nature Communications, not only provides new knowledge about the animal more than 250 years after it was first described but also opens up new avenues of research into the origin and production of strong electric discharges in other fish species.

Gymnotiformes, the knifefish family to which Gymnotidae belong, are native to Mexico and South America, are found almost exclusively in freshwater habitats, and are mostly nocturnal. There are currently approximately 250 valid gymnotiform species among 34 genera and five families.

A new species of electric eel produces the highest voltage discharge of any known animal phys.org/news/2019-09-species-electric-eel-highest-voltage.html via @physorg_com

[Ichthyology • 2019] Gymnotus darwini • A New Species of the Electric Knifefish Gymnotus Linnaeus (Gymnotiformes: Gymnotidae) from Northeastern Brazil

Gymnotus darwini 

Campos-da-Paz & de Santana, 2019

 DOI:  10.1643/CI-18-141

twitter.com/ASIHCopeia

Abstract

A new species of Gymnotus is described from coastal river systems in the Pernambuco State, Brazil. It is phylogenetically referred to the “Gymnotus carapo group clade” for presenting a clear patch posteriorly at anal fin, two independent pores at dorsoposterior corner of preopercle, a single row of well-developed teeth (most arrowhead-shaped) anteriorly on premaxilla, cleithrum with anterior notch, and by the relative anus to anal-fin distance, pectoral-fin length, and maxilla length. The new species is distinguished from all congeners in the “Gymnotus carapo group clade” by a unique set of characters of uncertain polarity, including the number of dark bands along the body, dark bands along body three to four times wider than pale interbands, with nearly straight margins (never broken anteriorly into irregular dark spots), and bands nearly uniform in color, number of scales above lateral line, number of lateral-line perforated scales to first ventral ramus, number of total pored lateral-line scales, head length, snout length, body depth, number of anal-fin rays, number of pectoral-fin rays, number of precaudal vertebrae, number of teeth on anterior row of premaxilla, and number of teeth along outer row of dentary. The new taxon represents the first species of Gymnotus described from localities in northeastern Brazil, north of the mouth of the rio São Francisco.

Fig. 1. Gymnotus darwini, MNRJ 51333, holotype, 157.0 mm TL,
Brazil, Pernambuco, Igarassu municipality, Refugio Ecológicos Charles Darwin, Igarapé Jacoca (or Tabatinga), rio Botafogo drainage. 

Gymnotus darwini, new species 

Etymology.— The specific epithet, darwini, is a patronym honoring Charles Robert Darwin (1809–1882), English naturalist, well known from his extensive and genial contribution to the study of evolution through natural selection, and because the holotype and a number of paratypes were collected at the Refúgio Ecológico Charles Darwin (RECD; rio Botafogo drainage, Igarassu, Pernambuco, Brazil). Darwin himself visited Pernambuco (Recife, Olinda, and vicinities) between the 12th and 19th of August 1836, while aboard of the H.M.S. Beagle (see Darwin, 1839).

Ricardo Campos-da-Paz and Carlos David de Santana. 2019. A New Species of the Electric Knifefish Gymnotus Linnaeus (Gymnotiformes: Gymnotidae) from Northeastern Brazil. Copeia. 107(1),; 144–151. DOI:  10.1643/CI-18-141  

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[Ichthyology • 2018] Revision of Gymnotus (Gymnotiformes: Gymnotidae) from the Upper Madeira Basin of Bolivia and Peru, with Descriptions of Two New Species; Gymnotus eyra & G. riberalta

Gymnotus eyra & G. riberalta 

Craig, Correa-Roldán, Ortega, Crampton & Albert, 2018

 DOI:  10.11646/zootaxa.4413.1.3 
  twitter.com/MJBernt 

Abstract

Banded Knifefishes (Gymnotus, Gymnotidae) comprise the most species-rich genus of Neotropical electric fishes, with 41 species currently described from throughout the humid Neotropics, from Mexico to Argentina. Despite substantial alpha-taxonomic work in recent years, the diversity of Gymnotus in some regions remains poorly understood. Here we describe the Gymnotus fauna of the Upper Madeira basin of Bolivia and Peru from examination of more than 240 adult specimens. Species are delimited and described using body proportions (traditional morphometrics), fin-ray, squamation and laterosensory-pore counts (meristics), quantitative shape differences (geometric morphometrics), osteological traits, and color patterns. Comparisons of standardized linear measures as well as multivariate statistical methods validate the presence in the Upper Madeira basin of three previously described species, two with wide-spread geographic distributions throughout Greater Amazonia (G. carapo and G. coropinae), and one (G. chaviro) endemic to southwestern Amazonia. We also diagnose and describe two new species that are endemic to the Upper Madeira basin: G. eyra n. sp., morphologically most similar to G. mamiraua from lowland Amazonia, and G. riberalta n. sp., morphologically most similar to G. pantanal from the Paraguay-Paraná basin. The five Gymnotus species from the Upper Madeira basin are not monophyletic, each species being more closely related to a different species from another region; i.e. the Gymnotus species from the Upper Madeira represents a polyphyletic assemblage. These descriptions to 43 the number of valid Gymnotus species.

Keywords: Pisces, Alpha taxonomy, biodiversity assessment, neotropical, species delimitation

Jack M. Craig, Vanessa Correa-Roldán, Hernán Ortega, William G. R. Crampton and James S. Albert. 2018.  Revision of Gymnotus (Gymnotiformes: Gymnotidae) from the Upper Madeira Basin of Bolivia and Peru, with Descriptions of Two New Species.  Zootaxa. 4413(1); 111–132. 

DOI:  10.11646/zootaxa.4413.1.3
Researchgate.net/publication/324654496_Revision_of_Gymnotus_from_the_Upper_Madeira_Basin_of_Bolivia_and_Peru

 twitter.com/MJBernt/status/987419735498293248

[Ichthyology • 2018] Gymnotus cuia • Revision of Banded Knifefishes of the Gymnotus carapo and G. tigre clades (Gymnotidae Gymnotiformes) from the Southern Neotropics

Gymnotus cuia

Craig, Malabarba, Crampton & Albert, 2018

 DOI: 10.11646/zootaxa.4379.1.3 

Abstract

Banded Knifefishes (Gymnotus, Gymnotidae) comprise the most species-rich, ecologically tolerant (eurytopic), and geographically widespread genus of Neotropical electric fishes (Gymnotiformes), with 40 valid species occupying most habitats and regions throughout the humid Neotropics. Despite substantial alpha-taxonomic work in recent years, parts of the genus remain characterized by taxonomic confusion. Here we describe and delimit species of the G. carapo and G. tigre clades from the southern Neotropics, using body proportions (caliper-based morphometrics), fin-ray, scale and laterosensory-pore counts (meristics), quantitative shape differences (geometric morphometrics), osteology, color patterns and electric organ discharges. We report these data from 174 Gymnotus specimens collected from 100 localities throughout the southern Neotropics, and delimit species boundaries in a multivariate statistical framework. We find six species of the G. carapo clade (G. carapo australis, Gymnotus cuia n. sp., G. chimarrao, G. omarorum, G. pantanal, and G. sylvius), and two species of the G. tigre clade (G. inaequilabiatus and G. paraguensis) in the southern Neotropics. The new species G. cuia is readily distinguished from the morphologically similar and broadly sympatric G. c. australis by a shorter head and deeper head and body, and from the morphologically similar and sympatric G. omarorum by fewer lateral-line ventral rami and fewer pored lateral-line scales anterior to the first ventral ramus. We also review the geographic distributions of all eight species of the G. carapo and G. tigre clades in the southern Neotropics, showing that G. cuia is the most widespread species in the region. These results affirm the importance of understanding the structure of variation within and between species, both geographic and ontogenetic, in delimiting species boundaries.

Keywords:  Pisces, Alpha taxonomy, Biodiversity assessment, Neotropical, Species delimitation

FIGURE 7. Variation within the type series of Gymnotus cuia.
A. The holotype, UFRGS 23700 (193 mm). B. Four specimens of the paratype series, UFRGS 9794 (171-217 mm).

Gymnotus cuia n. sp.

 G. aff. carapo — (Bertaco et al. 2016; Cognato et al. 2007a; b;
Cognato & Fialho 2006; Malabarba et al. 2013; Serra et al. 2014).

Etymology: The specific epithet is derived from the species’ especially deep body and head, evoking the short, rounded cuia gourd used to drink the traditional mate popular throughout its range. The convention of honoring this practice in gymnotiform taxonomy is shared with G. chimarrao (chimarrão =the mate itself) and Brachyhypopomus bombilla (bombilla = the metal straw used for drinking mate). The common name “ bombilla ” is often used to describe gymnotiform fish throughout the southern Neotropics as well.

Ecology: Gymnotus cuia inhabits lakes and small streams, associated to densely vegetated areas. The species is abundant in the type locality (Figure 9), a shallow lake (less than 1 m deep) with dense emergent vegetation, including Ludwigia peploides (Onagraceae), Utricularia spp. (Lenticulariaceae), Nymphoides indica (Menyanthaceae), Pontederia lanceolata (Pontederiaceae), Azolla sp. (Azollaceae), Eleocharis sp. (Cyperaceae), Cabomba australis (Cabombaceae), Echinodorus sp. (Alismataceae), Lemna valdiviana (Lemnaceae), Scirpus sp. (Sciperaceae) and abundant grass in the shores (Cognato & Fialho 2006). Throughout its distribution it is usually abundant in the roots of dense beds of floating water hyacinths (Eichornia crassipes). Reproductive cycle extends from November to March (Cognato & Fialho 2006).

FIGURE 9. Habitat and live appearance of Gymnotus cuia.
 A. The type locality of G. cuia, Lagoa Verde, Itapuã State Park, Viamão, Rio Grande, do Sul, Brazil. Photo: Diego Cognato. B. Close-up photo of the head of a live G. cuia. Photo: Will Crampton. C. Fullbody photo of of a live G. cuia. Photo: Will Crampton.

Jack M. Craig, Luiz R. Malabarba, William G. R. Crampton and James S. Albert. 2018. Revision of Banded Knifefishes of the Gymnotus carapo and G. tigre clades (Gymnotidae Gymnotiformes) from the Southern Neotropics.  Zootaxa. 4379(1); 47–73.    DOI: 10.11646/zootaxa.4379.1.3

ResearchGate.net/publication/323151053_Revision_of_Banded_Knifefishes_of_the_Gymnotus_carapo_and_G_tigre_clades_from_the_Southern_Neotropics

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[Ichthyology • 2014] Gymnotus capitimaculatus • A New Species of Electric Fish (Gymnotiformes: Gymnotidae) from rio Jucuruçu basin, northeastern Brazil

Gymnotus capitimaculatus 

 Rangel-Pereira, 2014 

Abstract

A new species of Gymnotus, from the G. pantherinus species-group, is herein described from the rio Jucuruçu basin, a coastal river drainage located in the southern part of Bahia state, northeastern Brazil. Gymnotus capitimaculatus sp. n. differs from all congeners by having an pair of round blotches anteriorly positioned or under vertical passing through eye, on ventral portion of the head. Furthermore, Gymnotus capitimaculatus also differs from all members of the G. pantherinus species-group by having the following unique combination of characters states: tail with an unique series of bands or round spots; precaudal portion of trunk without bands but either with rounded and/or vermiculated spots; forty-five precaudal vertebrae; nine scales above lateral line at mid-body; anal-fin base length 75.2–78.6 % of TL; anus-anal fin length 101.4–122.8 % of HL; and branchial opening 38.5–45.0 % of HL.

Key words: Atlantic Forest, Biodiversity, electric eels, Gymnotus pantherinus complex, Knife-fish, taxonomy

Distribution. Known only from rio do Ouro, a tributary of the rio Jucuruçu, Itamaraju municipality, Bahia state, northeastern Brazil.

Etymology. Named capitimaculatus from the Latin subject capitis (head) and adjective maculatus (blotchy), due to the presence of a pair of blotches in the ventral portion of the head. 

Ecology. The specimens were collected in a clear water stream which topical width was about 1.5 m, depth ranged from 0.1 to 1 m and the bottom was composed of sand and small gravel. The matrix through where the stream flowed was composed of a mix of grass pasture and scarce riparian forest. Individuals were found deeply hidden among marginal vegetation and roots, mostly where the water flow was faster. Another species of the genus Gymnotus, belonging to the G. carapo species group, was found sympatrically, but not syntopically, since it was caught where the water flow was slower.

 Rangel-Pereira F.S. 2014. Gymnotus capitimaculatus, A New Species of Electric Fish from rio Jucuruçu basin, northeastern Brazil (Ostariophysi: Gymnotiformes: Gymnotidae). Vertebrate Zoology. 64(2); 169–175. 

http://www.senckenberg.de/files/content/forschung/publikationen/vertebratezoology/vz64-2/02_vertebrate_zoology_64-2_rangel-pereira_169-175.pdf

Resumo: Uma nova espécie de Gymnotus, pertencente ao grupo de espécies G. pantherinus, é aqui descrita para a bacia do rio Jucuruçu, uma drenagem fluvial costeira localizada no sul do estado da Bahia, nordeste do Brasil. Gymnotus capitimaculatus sp. n. difere de todos seus congêneres por possuir a porção ventral da cabeça com um par de máculas posicionadas anteriormente ou sob vertical que passa pelo olho. Ademais, Gymnotus capitimaculatus também difere de todos os membros do grupo G. pantherinus pela seguinte combinação exclusiva de caracteres: cauda com uma única série de barras os manchas arredondadas; porção pré-caudal do tronco sem barras ou com manchas arredondadas ou vermiculadas; quarenta e cinco vértebras pré-caudais; nove escamas acima da linha lateral no meio do corpo; comprimento da base da nadadeira anal 75,2–78,6 % do TL; comprimento ânus-nadadeira anal 101,4–122,8 % do HL; e abertura branquial 38,5 –45,0 % do HL.