Maria Isabela Moreira Uliam1, Helena Paulino Amorim Ribeiro1 and Guilherme Moreira Dutra2 
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Associate Editor: George Mattox
Section Editor: William Crampton
Editor-in-chief: José Birindelli
Abstract
Uma espécie nova de Eigenmannia é descrita da bacia do rio Negro, Brasil, com base em conjuntos de dados morfológicos e moleculares. A espécie nova distingue-se de todas as congêneres pela seguinte combinação de caracteres: boca subterminal, ausência da faixa da linha lateral, ausência da faixa médio-lateral superior, diâmetro do olho correspondendo à 23,0–29,3% do comprimento da cabeça, ii,14–17 raios na nadadeira peitoral, 185–225 raios na nadadeira anal, 21–27 dentes no pré-maxilar, 11–16 dentes no dentário, 4–8 dentes no endopterigóide, e primeiro basibranquial não ossificado. Adicionalmente, sequências do gene citocromo oxidase I foram obtidas de quatro amostras para testar a congruência entre conjuntos de dados moleculares e morfológicos, aplicando três análises moleculares de delimitação de espécies: ASAP (Assemble Species by Automatic Partitioning), PTP (Poisson Tree Processes) e bPTP (Bayesian Poisson tree processes). As análises ASAP e PTP recuperaram a espécie nova como uma única MOTU (unidade taxonômica operacional molecular), enquanto a bPTP estimou três MOTU’s para esta linhagem. A espécie nova também apresenta divergência genética significativa em relação aos seus congêneres, variando de 8,7 a 17,3%. Inconsistências entre análises moleculares de delimitação de espécies, a implicação filogenética da presença de olhos grandes e a diversidade de Eigenmannia na bacia do rio Negro são discutidas.
Palavras-chave: Biodiversidade, Delimitação molecular de espécies, Eigenmannia macrops, Peixes elétricos,Taxonomia integrativa.
Introduction
Eigenmannia Jordan & Evermann, 1896, includes 31 valid species, widely distributed over major cis- and trans- Andean drainages of South America and Panama (Ferraris et al., 2017; Fricke et al., 2024). Despite recent efforts to describe its diversity (e.g., Herrera-Collazos et al., 2020; Cardoso, Dutra, 2023), the genus remains one of the most complex within the Gymnotiformes. Dutra et al. (2024) revised the identification of Eigenmannia vouchers for COI sequences available in online repositories, providing a solid database for an integrative approach into the genus. These authors also employed molecular species delimitation analysis broadly applied in taxonomic studies of Neotropical Fishes (e.g., Boaretto et al., 2024; Martins et al., 2024), such as Assemble Species by Automatic Partitioning (ASAP: Puillandre et al., 2021) and Poisson Tree Processes (PTP; Zhang et al., 2013), to support the description of a new species. Dutra et al. (2024) also highlighted that most taxonomic uncertainties in Eigenmannia involve species from the Amazon-Orinoco-Guiana region, where at least six undescribed lineages were recovered (Dutra et al., 2024: figs. 11–12). Up to now, fourteen Eigenmannia species are known from this region: E. antonioi Peixoto, Dutra & Wosiacki, 2015, from the rio Anapu basin; E. limbata (Schreiner & Miranda Ribeiro, 1903), widespread in the Amazon-Orinoco-Guiana region; E. loretana Waltz & Albert, 2018, from the Western Amazon; E. macrops (Boulenger, 1897), widespread in the Amazon-Orinoco-Guiana region; E. macuxi Dutra, Peixoto, Donin, de Santana & Menezes, 2024, from the rio Branco basin; E. matintapereira Peixoto, Dutra & Wosiacki, 2015, from the rio Negro basin; E. muirapinima Peixoto, Dutra & Wosiacki, 2015, from small tributaries of the rio Amazonas; E. nigra Mago-Leccia, 1994, widespread in the Amazon-Orinoco-Guiana region; E. oradens Dutra, Peixoto, de Santana & Wosiacki, 2018, from the rio Ventuari basin; E. pavulagem Peixoto, Dutra & Wosiacki, 2015, from the rio Guamá basin; E. sayona Peixoto & Waltz, 2017, from the río Orinoco basin; E. sirius Peixoto & Ohara, 2019, from the rio Tapajós basin; E. vicentespelaea Triques, 1996, from the rio Tocantins basin; and E. waiwai Peixoto, Dutra & Wosiacki, 2015, from the rio Trombetas basin. Still, the taxonomic status of many populations of Eigenmannia in the Amazon-Orinoco-Guiana region, especially those from tributaries of the rio Amazonas, remains poorly understood. Consequently, many of these undescribed species are tentatively identified as either E. trilineata López & Castello, 1966 or E. virescens (Valenciennes, 1836) in fish inventories (e.g., Beltrão et al., 2019; Dagosta, de Pinna, 2019), two species that are known from the Paraná-Paraguay basin (Peixoto et al., 2015).
In this study, we focused on a population of Eigenmannia from the rio Negro that resembles E. macuxi. However, further examination of this material, including assessment of morphological and molecular characters, identified it as an undescribed species, which is described herein.
Material and methods
Morphological analysis. All measurements were taken to the nearest 0.1 mm with digital calipers under a stereomicroscope, preferably on the left side. Measurements and counts followed Peixoto et al. (2015). Measurements reported as the percentage of total length and length to end of anal-fin base are given only for specimens without damage or tail regeneration. In the description, frequencies are given in parentheses after each count, and an asterisk indicates counts for the holotype. The type-series includes only specimens from which morphological and/or molecular data were taken. The nomenclature of stripes follows Peixoto et al. (2015) and Peixoto, Wosiacki (2016), as illustrated by Dutra et al. (2022: fig. 1). Osteological data were obtained from seven cleared and stained specimens according to Taylor, Van Dyke (1985). Replacement teeth were not included in teeth counts. Precaudal vertebrae included four vertebrae of the Weberian complex plus all remaining vertebrae without fully developed hemal spines. Transitional vertebrae are post-Weberian precaudal vertebrae lacking both pleural ribs and hemal spines (Hopkins, 1991).
Molecular data and analysis. The molecular species delimitation analyses were based on an expanded version of the COI matrix for the genus Eigenmannia from Dutra et al. (2024). In addition to the samples examined by these authors, four COI sequences from specimens of the new species were generated and incorporated into the matrix (Tab. 1). Total genomic DNA was extracted using Promega Genomic DNA Purification Kit, according to the manufacturer’s protocol. We optimized PCR conditions to amplify a 652 base pair (bp) fragment of the mitochondrial Cytochrome c oxidase subunit I protein-coding gene (COI) using the primers FishF6 and FishR7 (Jennings et al., 2019). PCR reactions were performed using a solution with a total volume of 12.5 μl, with 8.55 μl of ultra-pure water, 1.25 μl of 10X PCR buffer, 0.5 μl of MgCl2, 0.5 μl dNTPs (200 nM of each), 0.25 μl each 5 mM primer, 0.2 μl Taq DNA Polymerase (pht), 1 μl DNA template (10–50 ng). The thermo-cycler profile consisted of an initial denaturation (3 min at 95ºC) followed by 30 cycles of chain denaturation (30 s at 94ºC), primer hybridization (45 s at 52ºC), and nucleotide extension (60 s at 68ºC), followed by a final extension (7 min at 68ºC). PCR products were analyzed using electrophoresis in agarose gel and purified using ExoSap-ITVR (USB Corporation) following manufacturer’s instructions. Purified PCR products were sequenced in the Instituto de Biotecnologia (IBTEC) – Campus de Botucatu, Brazil. Consensus sequences for each sample were assembled from chromatograms for forward and reverse sequences and posteriorly aligned in Geneious software using the MUSCLE algorithm (Edgar, 2004) under default parameters.
TABLE 1 | Tissue samples of Eigenmannia wazowskii used in the present study.
Voucher | Tissue number | Genbank Accession number | Locality |
INPA 42778 | P18052 | PX056314 | Rio Negro, São Gabriel da Cachoeira |
INPA 42823 | P18176 | PX056315 | Rio Negro, São Gabriel da Cachoeira |
LBP 26813 | 97223 | PX056316 | Rio Aracá, Barcelos |
LBP 26803 | 97392 | PX056317 | Rio Aracá, Barcelos |
Three molecular species delimitation analyses were conducted to test the congruence between molecular and morphological datasets (external and internal anatomical characters). The Poisson tree processes (PTP) and the bayesian Poisson tree processes (bPTP) (Zhang et al., 2013) were implemented via a non-ultrametric best maximum likelihood tree estimated in IQ-TREE web server (http://iqtree.cibiv.univie.ac.at/) (Trifinopoulos et al., 2016) under an Ultrafast Bootstrap analysis (Hoang et al., 2018), and the remaining parameters with default values. Maximum likelihood tree was rooted in Sternopygus macrurus (Bloch & Schneider, 1801). The PTP and bPTP analyses were performed in the PTP server (https://species.h-its.org/ptp/) under default values. The Assemble Species by Automatic Partitioning (ASAP – Puillandre et al., 2021) was employed in ASAP web server (https://bioinfo.mnhn.fr/abi/public/asap/). Additionally, we estimated pairwise genetic distances for COI matrix in Mega 11 (Tamura et al., 2021) using Kimura 2-parameter model, K2P (Kimura, 1980).
Abbreviations. Institutional abbreviations follow Sabaj (2020, 2025). Abbreviations used in the text are HL = head length, LEA = length to end of anal-fin base, MOTU = molecular operational taxonomical unit, cs = cleared and counterstained specimens, and xr = radiographed.
Results
Eigenmannia wazowskii, new species
urn:lsid:zoobank.org:act:9FF73E23-839E-442D-81B6-2AA882087960
(Figs. 1–2; Tab. 2)
Holotype. MZUSP 130864, 180.9 mm LEA, rio Tarumã-Mirim, rio Negro basin, Manaus, Amazonas, Brazil, 03°05’45”S 60°10’38”W, 9 Oct 1994, M. Weastneat.
Paratypes. All from Brazil, rio Negro basin. INPA 42778, 2, 99.8–100.8 mm LEA, rio Negro at Praia do Jáu, São Gabriel da Cachoeira, Amazonas, 00°08’13”S 67°04’59”W, 1 Dec 2013, L. Rapp Py-Daniel, D. Bastos, R. Silva, P. Ito & M. Pinna. INPA 42823, 2, 77.7–79.3 mm LEA, rio Negro at praia do acampamento, São Gabriel da Cachoeira, Amazonas, 00°03’04”S 67°16’32”W, 2 Dec 2013, L. Rapp Py-Daniel, D. Bastos, R. Silva, P. Ito & M. Pinna. LBP 26803, 1, 86.6 mm LEA, rio Aracá, Barcelos, Amazonas, 00°24’54.4”S 62°56’09.1”W, 11 Aug 2018, G. Costa e Silva, M. Bernt & B. Waltz. LBP 26813, 2, 69.8–72.5 mm LEA, rio Aracá, Barcelos, Amazonas, 00°24’23.4”S 62°56’08.1”W, 11 Aug 2018, G. Costa e Silva, M. Bernt & B. Waltz. LBP 35674, 5, 68.1–89.5 mm LEA, rio Negro, Santa Isabel do Rio Negro, Amazonas, 00°30’05.3”S 64°49’12.2”W, 16 Aug 2013, C. Oliveira & M. Taylor. MZUSP 66665, 20 (3 cs), 73.0–90.9 mm LEA, MZUSP 130865, 39 (4 cs), 72.0–178.9 mm LEA, same data as the holotype.
Non-types. All from Brazil, rio Negro basin. INPA 28918, 21, 60.6–91.4 mm LEA, rio Negro, Rorainópolis, Roraima, 01°24’50”S 61°37’34”W, 21 Feb 2008, J. Maldonado & U. Jaramillo. INPA 37801, 3, 67.8–86.3 mm LEA, rio Daraá, Santa Isabel do Rio Negro, 00°25’51”S 64°45’46”W, 31 Mar 2012, J. Zuanon, H. Espírito-Santo, R. Leitão, R. Rala, T. Hrbek & P. Ito. INPA 37818, 1, 84.3 mm LEA, rio Aiuanã, Santa Isabel do Rio Negro, 00°34’31”S 64°55’35”W, 1 Apr 2012, J. Zuanon, H. Espírito-Santo, R. Leitão, R. Rala, T. Hrbek & P. Ito. INPA 49534, 15, 67.6–81,7 mm LEA, rio Negro near Yawawira community, São Gabriel da Cachoeira, 00°03’26.3”N 67°16’31.2”W, 23 Feb 2015, D. Bastos & A. Bifi. INPA 51539, 1, 78.1 mm LEA, rio Padauari near confluence with rio Preto, Santa Isabel do Rio Negro, 00°06’45.7”S 64°05’09.2”W, 22 Jul 2014, E. Ferreira, S. Hashimoto & J. Pena. INPA 58902, 3, 91.1–100.5 mm LEA, Igarapé Pedral, Santa Isabel do Rio Negro, Amazonas, 00°23’15”S 64°29’05”W, 5 Apr 2019, C. Deus, A. Martins & D. Castanho. MZUSP 29977, 1, 193.6 mm LEA, rio Daraá at Cachoeira do Aracu, Santa Isabel do Rio Negro, Amazonas, 10 Feb 1980, M. Goulding. MZUSP 29987, 5, 64.7–80.4 mm LEA, rio Negro at Massarabi community, Santa Isabel do Rio Negro, Amazonas, 18 Oct 1979, M. Goulding. MZUSP 124285, 90 (not measured), same data as holotype.
Diagnosis. Eigenmannia wazowskii differs from all congeners, except E. besouro Peixoto & Wosiacki, 2016, E. bumba Dutra, Ramos & Menezes, 2022, E. camposi Herrera-Collazos, Galindo-Cuervo, Maldonado-Ocampo & Ríncon-Sandoval, 2020, E. correntes Campos-da-Paz & Queiroz, 2017, E. dutrai Peixoto, Pastana & Ballen, 2021, E. macuxi, E. oradens, E. robsoni Dutra, Ramos & Menezes, 2022, E. sirius, E. vicentespeleaea, E. virescens, and E. waiwai by having a subterminal mouth (versus terminal). It differs from all the aforementioned species, except from E. robsoni and E. virescens, by the absence of lateral-line stripe (vs. presence). The new species differs from E. robsoni by having 21–27 premaxillary teeth (vs. 32–34), 11–16 dentary teeth (vs. 35–44), and 4–8 endopterygoid teeth (vs. 9–12); and from E. virescens by having 11–16 dentary teeth (vs. 39), 4–8 endopterygoid teeth (vs. 9), and the basibranchial 1 unossified (vs. ossified). Eigenmannia wazowskii is additionally diagnosed from abovementioned species by the following combination of characters: (1) eye diameter corresponding to 22.0–29.3% of HL (vs. 10.6–13.3% of HL in E. correntes, 14.4–20.3% of HL in E. dutrai, and 5.0–18.0% of HL in E. vicentespelaea); (2) ii,14–17 pectoral-fin rays (vs. ii,12–13 in E. correntes); (3) 185–225 anal-fin rays (vs. 143–154 in E. correntes, and 157–183 in E. sirius); (4) 21–27 premaxillary teeth (vs. 11–20 in E. correntes, 36 in E. oradens, and 28–29 in E. waiwai); (5) 11–16 dentary teeth (vs. 19–30 in E. besouro, 20–29 in E. bumba, 20–22 in E. camposi, 35–36 in E. dutrai, 19–23 in E. macuxi, 30 in E. oradens, 38–41 in E. vicentespelaea, and 32–36 in E. waiwai); and (6) 4–8 endopterygoid teeth (vs. 10–11 in E. besouro, 9–10 in E. camposi, 9–18 in E. dutrai, 10 in E. oradens, 9–13 in E. sirius and E. vicentespelaea, and 14–17 in E. waiwai). Further, E. wazowskii differs from E. macrops (Boulenger, 1897) by having a subterminal mouth (vs. terminal), and 11–16 dentary teeth (vs. 20–27); and from the E. humboldtii species-group by having 185–225 (mode 201) anal-fin rays (vs. more than 220 rays).
Description. External morphology. Body shape and pigmentation in Fig. 1, morphometric data in Tab. 2. Largest specimen 180.9 mm LEA. Body elongated and distinctly compressed laterally. Greatest body depth at vertical through distal tip of pectoral fin. Dorsal profile of body slightly convex from snout tip to vertical through anal-fin terminus. Ventral profile of body nearly straight from tip of lower jaw to vertical through tip of pectoral fin and concave from this point to anal-fin terminus. Caudal filament short.
FIGURE 1| Eigenmannia wazowskii, MZUSP 130864, holotype, 180.9 mm LEA, rio Tarumã-Mirim, rio Negro basin, Amazonas, Brazil; (A) lateral view of head; (B) lateral view of body.
TABLE 2 | Morphometrics for examined specimens of Eigenmannia wazowskii. Range includes values for holotype. SD = Standard deviation; N = Number of specimens.
| Holotype | Range | Mean | SD | N |
Total length (mm) | 233.6 | 92.3–223.6 | – | – | 25 |
Length to end of anal fin (mm) | 180.9 | 69.8–180.9 | – | – | 25 |
Head length (mm) | 23.1 | 9.4–23.1 | – | – | 25 |
Caudal-filament length (mm) | 52.7 | 20.3–71.5 | – | – | 25 |
Percent of length to the end of anal fin | |||||
Caudal-filament length | 29.1 | 24.6–61.0 | 38.4 | 10.3 | 22 |
Greatest body depth | 12.2 | 10.9–15.8 | 13.7 | 1.2 | 25 |
Body depth at anal-fin origin | 11.5 | 9.6–13.9 | 12.0 | 1.2 | 25 |
Body width | 4.3 | 4.0–7.1 | 5.1 | 0.7 | 25 |
Preanal-fin distance | 15.5 | 11.4–20.0 | 17.2 | 1.8 | 25 |
Prepectoral-fin distance | 13.4 | 12.6–17.1 | 14.8 | 1.2 | 25 |
Anal-fin length | 85.1 | 74.4–86.0 | 81.2 | 3.5 | 25 |
Pectoral-fin length | 8.7 | 8.3–13.1 | 10.6 | 1.3 | 25 |
Snout to anus | 7.8 | 7.7–12.5 | 10.7 | 1.3 | 25 |
Head length | 12.8 | 11.8–16.7 | 13.6 | 1.1 | 25 |
Percent of head length | |||||
Head width at opercle | 54.0 | 38.6–62.3 | 48.7 | 5.7 | 25 |
Head width at eye | 36.3 | 29.0–51.9 | 35.5 | 5.1 | 25 |
Head depth at nape | 67.5 | 65.3–88.8 | 74.5 | 5.4 | 25 |
Head depth at eye | 48.5 | 44.7–63.5 | 55.5 | 5.0 | 25 |
Snout length | 33.3 | 23.0–35.1 | 28.3 | 3.4 | 25 |
Snout to posterior nostril | 21.5 | 15.4–23.9 | 20.4 | 2.1 | 25 |
Posterior nostril to eye | 7.5 | 3.6–7.7 | 5.6 | 1.3 | 23 |
Postorbital distance | 50.1 | 47.3–61.6 | 53.6 | 4.3 | 25 |
Branchial opening | 26.0 | 24.2–39.2 | 31.5 | 5.0 | 25 |
Internarial width | 15.1 | 10.5–19.3 | 14.2 | 2.2 | 25 |
Internarial distance | 10.3 | 8.3–13.6 | 10.7 | 1.3 | 25 |
Interorbital distance | 20.9 | 16.5–26.4 | 20.3 | 2.9 | 24 |
Eye diameter | 25.5 | 22.0–29.3 | 25.6 | 1.9 | 25 |
Mouth length | 20.3 | 16.8–24.8 | 21.0 | 2.1 | 25 |
Mouth width | 15.5 | 14.8–23.3 | 18.0 | 1.8 | 25 |
Percent of caudal-fin length | |||||
Caudal-filament width | 3.5 | 0.6–3.5 | 1.4 | 0.8 | 21 |
Caudal-filament depth | 5.8 | 1.2–7.4 | 3.3 | 1.5 | 21 |
Head laterally compressed; greatest width at opercular region, greatest depth at nape. Dorsal profile of head convex from snout tip to nape. Ventral profile of head nearly straight from tip of lower jaw to isthmus. Snout pointed in lateral view. Mouth subterminal. Mouth rictus at vertical through a point between anterior and posterior nares or vertical through posterior nostril. Anterior nostril tube-like, closer to snout tip than to anterior margin of eye. Posterior nostril round, closer to anterior margin of eye than to snout tip, at horizontal line between middle and dorsal margin of eye. Eye small, circular, completely covered by skin, on anterior one-half of HL, laterally oriented. Anus adjacent to urogenital papilla, shifting ontogenetically from vertical through posterior to anterior margin of opercle. Urogenital papilla not developed in specimens under 132.8 mm LEA. Branchial membranes joined at isthmus.
Scales cycloid and small, extending from posterior most part of head to vertical through tip of caudal filament, present on mid-dorsal region of body. Scales above lateral line at vertical through end of pectoral fin 8(1), 9(1), 10*(9), 11(10), or 12(4). Anterior most perforated lateral-line scales along vertical through pectoral-fin origin. Lateral-line scales to vertical through base of last anal-fin ray 104(1), 106(1), 107(1), 108(1), 109(1), 110(2), 112(2), 113(3), 116(1), 117(1), 119*(3), 120(2), 121(1), 122(2), 124(1), 126(1), or 129(2). Pectoral-fin rays ii,14(4), ii,15*(7), ii,16(12), or ii,17(2). Distal pectoral-fin margin straight. Total anal-fin rays 185(1), 189(1), 190(1), 191(2), 192(1), 193(1), 194(1), 197(1), 199(1), 202(3), 203(2), 205(1), 207(3), 208(1), 212(2), 217(1), 219(1), 225*(1). Anal-fin origin along vertical through pectoral-fin insertion or slightly posterior. Distal margin of anal fin slightly convex. First unbranched anal-fin rays tiny, subsequent rays progressively increasing in size toward first branched rays. Branched anal-fin rays of nearly the same length except for posterior most rays that progressively decrease in length.
Relevant osteological features. Premaxillary teeth 21(1), 23(3), 24(1), 25(1), or 27(1) arranged in three (4), or four (3) rows. Dentary teeth 11(2), 13(1), 14(1), or 16(3) arranged in single (3), or two (4) rows. Endopterygoid teeth four (1), five (2), seven (3), or eight (1). Upper pharyngeal teeth eight (1), nine (32), or 10(4). Lower pharyngeal teeth nine (4), 10(2), or 11(1). Precaudal vertebrae 13(5), 14(1), or 15(1). Transitional vertebrae four (7). Pleural ribs five (2), or six (5). Displaced hemal spines two (1), or three (6).
Coloration in alcohol. Body ground coloration cream. Body with two layers of chromatophores. Outer layer covered by melanophores gradually more spaced ventrally. Lateral-line stripe, and inferior midlateral stripe absent. Superior midlateral stripe present or absent. Inner layer of pigmentation formed by multiple, small bars of dark chromatophores situated between the musculature associated with anal-fin pterygiophores (inclinatores anales). Dark individual bars in combination forming anal-fin base stripe. Head covered by dark chromatophores, more concentrated on dorsal region gradually more spaced ventrally. Pectoral and anal fins hyaline with scattered dark chromatophores overlying fin rays.
Geographical distribution. Eigenmannia wazowskii is known only from the rio Negro basin, Amazonas, Brazil (Fig. 3).
FIGURE 2| Jaws of Eigenmannia wazowskii, MZUSP 130865; (A) premaxilla, right side, ventral view, anterior on top; (B) lower jaw, inverted image, left side, medial view, anterior on left; (C) lower jaw zoom highlighting dentary teeth.
FIGURE 3| Map of northern portion of South America showing distribution of Eigenmannia wazowskii (white star for type-locality) in the rio Negro basin.
Etymology. The epithet “wazowskii” is in reference to Mike Wazowski, a fictional character from Disney/Pixar franchise Monsters Inc, that also has a large eye. To be treated in the genitive case, male.
Conservation status. Eigenmannia wazowskii apparently does not match any of the extinction risk categories given by the International Union for Conservation of Nature (IUCN). The species possesses a relatively broad distribution, being widespread in the rio Negro basin. Therefore, according to the currently available data, and using the criteria of the IUCN Standards and Petitions Subcommittee (IUCN, 2024), we propose that the species should be classified as Least Concern (LC).
Phylogenetic inference. The phylogenetic relationships and genetic distinctiveness of the new species and its congeners were investigated by an ML analysis. The best fit of nucleotide substitution estimated for the data was TN + F + I + G4. The phylogenetic reconstruction recovered E. macrops as a non-monophyletic species in which the two recovered lineages are successive sister groups of all Eigenmannia species. In turn, E. microstoma was recovered as the sister group of all other Eigenmannia species.
Eigenmannia wazowskii was recovered as the sister group of E. macuxi,and this clade is the sister group of a clade that includes E. besouro, E. catira, E. dutrai, E. vicentespelaea, E. virescens, Eigenmannia sp. “Barima”, Eigenmannia sp. “Maroni”, Eigenmannia sp. “Paraíba do Sul”, Eigenmannia sp. “Orinoco”, Eigenmannia sp. “Peru KR491591”, and Eigenmannia sp. “Purus”.
The Eigenmannia humboldtii species group was recovered as the sister clade of the lineage including E. guairaca, E. loretana, E. trilineata, Eigenmannia sp. “Peru KF533346–47”, and Eigenmannia sp. “unknown locality NC004701”. The trans-Andean Eigenmannia species was recovered as a monophyletic group being the sister group of all other Eigenmannia clades, except E. macrops and E. microstoma.
Molecular species delimitation. The ASAP lowest score recovered was 5.0, indicating the better partition, and recognizing 29 MOTU’s. In turn, PTP and bPTP results estimated respectively 27 and 41 MOTU’s (Fig. 4). ASAP and PTP analyses recovered E. wazowskii as a unique MOTU, whereas the bPTP estimated three MOTU’s in E. wazowskii. The overall mean genetic interspecific distances was 12.1±1.1%, with genetic distance between E. wazowskii and other lineages ranging from 8.7% with E. catira to 17.3% with E. loretana (Tab. S1).
Eigenmannia wazowskii, new species
urn:lsid:zoobank.org:act:9FF73E23-839E-442D-81B6-2AA882087960
(Figs. 1–2; Tab. 2)
Holotype. MZUSP 130864, 180.9 mm LEA, rio Tarumã-Mirim, rio Negro basin, Manaus, Amazonas, Brazil, 03°05’45”S 60°10’38”W, 9 Oct 1994, M. Weastneat.
Paratypes. All from Brazil, rio Negro basin. INPA 42778, 2, 99.8–100.8 mm LEA, rio Negro at Praia do Jáu, São Gabriel da Cachoeira, Amazonas, 00°08’13”S 67°04’59”W, 1 Dec 2013, L. Rapp Py-Daniel, D. Bastos, R. Silva, P. Ito & M. Pinna. INPA 42823, 2, 77.7–79.3 mm LEA, rio Negro at praia do acampamento, São Gabriel da Cachoeira, Amazonas, 00°03’04”S 67°16’32”W, 2 Dec 2013, L. Rapp Py-Daniel, D. Bastos, R. Silva, P. Ito & M. Pinna. LBP 26803, 1, 86.6 mm LEA, rio Aracá, Barcelos, Amazonas, 00°24’54.4”S 62°56’09.1”W, 11 Aug 2018, G. Costa e Silva, M. Bernt & B. Waltz. LBP 26813, 2, 69.8–72.5 mm LEA, rio Aracá, Barcelos, Amazonas, 00°24’23.4”S 62°56’08.1”W, 11 Aug 2018, G. Costa e Silva, M. Bernt & B. Waltz. LBP 35674, 5, 68.1–89.5 mm LEA, rio Negro, Santa Isabel do Rio Negro, Amazonas, 00°30’05.3”S 64°49’12.2”W, 16 Aug 2013, C. Oliveira & M. Taylor. MZUSP 66665, 20 (3 cs), 73.0–90.9 mm LEA, MZUSP 130865, 39 (4 cs), 72.0–178.9 mm LEA, same data as the holotype.
Non-types. All from Brazil, rio Negro basin. INPA 28918, 21, 60.6–91.4 mm LEA, rio Negro, Rorainópolis, Roraima, 01°24’50”S 61°37’34”W, 21 Feb 2008, J. Maldonado & U. Jaramillo. INPA 37801, 3, 67.8–86.3 mm LEA, rio Daraá, Santa Isabel do Rio Negro, 00°25’51”S 64°45’46”W, 31 Mar 2012, J. Zuanon, H. Espírito-Santo, R. Leitão, R. Rala, T. Hrbek & P. Ito. INPA 37818, 1, 84.3 mm LEA, rio Aiuanã, Santa Isabel do Rio Negro, 00°34’31”S 64°55’35”W, 1 Apr 2012, J. Zuanon, H. Espírito-Santo, R. Leitão, R. Rala, T. Hrbek & P. Ito. INPA 49534, 15, 67.6–81,7 mm LEA, rio Negro near Yawawira community, São Gabriel da Cachoeira, 00°03’26.3”N 67°16’31.2”W, 23 Feb 2015, D. Bastos & A. Bifi. INPA 51539, 1, 78.1 mm LEA, rio Padauari near confluence with rio Preto, Santa Isabel do Rio Negro, 00°06’45.7”S 64°05’09.2”W, 22 Jul 2014, E. Ferreira, S. Hashimoto & J. Pena. INPA 58902, 3, 91.1–100.5 mm LEA, Igarapé Pedral, Santa Isabel do Rio Negro, Amazonas, 00°23’15”S 64°29’05”W, 5 Apr 2019, C. Deus, A. Martins & D. Castanho. MZUSP 29977, 1, 193.6 mm LEA, rio Daraá at Cachoeira do Aracu, Santa Isabel do Rio Negro, Amazonas, 10 Feb 1980, M. Goulding. MZUSP 29987, 5, 64.7–80.4 mm LEA, rio Negro at Massarabi community, Santa Isabel do Rio Negro, Amazonas, 18 Oct 1979, M. Goulding. MZUSP 124285, 90 (not measured), same data as holotype.
Diagnosis. Eigenmannia wazowskii differs from all congeners, except E. besouro Peixoto & Wosiacki, 2016, E. bumba Dutra, Ramos & Menezes, 2022, E. camposi Herrera-Collazos, Galindo-Cuervo, Maldonado-Ocampo & Ríncon-Sandoval, 2020, E. correntes Campos-da-Paz & Queiroz, 2017, E. dutrai Peixoto, Pastana & Ballen, 2021, E. macuxi, E. oradens, E. robsoni Dutra, Ramos & Menezes, 2022, E. sirius, E. vicentespeleaea, E. virescens, and E. waiwai by having a subterminal mouth (versus terminal). It differs from all the aforementioned species, except from E. robsoni and E. virescens, by the absence of lateral-line stripe (vs. presence). The new species differs from E. robsoni by having 21–27 premaxillary teeth (vs. 32–34), 11–16 dentary teeth (vs. 35–44), and 4–8 endopterygoid teeth (vs. 9–12); and from E. virescens by having 11–16 dentary teeth (vs. 39), 4–8 endopterygoid teeth (vs. 9), and the basibranchial 1 unossified (vs. ossified). Eigenmannia wazowskii is additionally diagnosed from abovementioned species by the following combination of characters: (1) eye diameter corresponding to 22.0–29.3% of HL (vs. 10.6–13.3% of HL in E. correntes, 14.4–20.3% of HL in E. dutrai, and 5.0–18.0% of HL in E. vicentespelaea); (2) ii,14–17 pectoral-fin rays (vs. ii,12–13 in E. correntes); (3) 185–225 anal-fin rays (vs. 143–154 in E. correntes, and 157–183 in E. sirius); (4) 21–27 premaxillary teeth (vs. 11–20 in E. correntes, 36 in E. oradens, and 28–29 in E. waiwai); (5) 11–16 dentary teeth (vs. 19–30 in E. besouro, 20–29 in E. bumba, 20–22 in E. camposi, 35–36 in E. dutrai, 19–23 in E. macuxi, 30 in E. oradens, 38–41 in E. vicentespelaea, and 32–36 in E. waiwai); and (6) 4–8 endopterygoid teeth (vs. 10–11 in E. besouro, 9–10 in E. camposi, 9–18 in E. dutrai, 10 in E. oradens, 9–13 in E. sirius and E. vicentespelaea, and 14–17 in E. waiwai). Further, E. wazowskii differs from E. macrops (Boulenger, 1897) by having a subterminal mouth (vs. terminal), and 11–16 dentary teeth (vs. 20–27); and from the E. humboldtii species-group by having 185–225 (mode 201) anal-fin rays (vs. more than 220 rays).
Description. External morphology. Body shape and pigmentation in Fig. 1, morphometric data in Tab. 2. Largest specimen 180.9 mm LEA. Body elongated and distinctly compressed laterally. Greatest body depth at vertical through distal tip of pectoral fin. Dorsal profile of body slightly convex from snout tip to vertical through anal-fin terminus. Ventral profile of body nearly straight from tip of lower jaw to vertical through tip of pectoral fin and concave from this point to anal-fin terminus. Caudal filament short.
Head laterally compressed; greatest width at opercular region, greatest depth at nape. Dorsal profile of head convex from snout tip to nape. Ventral profile of head nearly straight from tip of lower jaw to isthmus. Snout pointed in lateral view. Mouth subterminal. Mouth rictus at vertical through a point between anterior and posterior nares or vertical through posterior nostril. Anterior nostril tube-like, closer to snout tip than to anterior margin of eye. Posterior nostril round, closer to anterior margin of eye than to snout tip, at horizontal line between middle and dorsal margin of eye. Eye small, circular, completely covered by skin, on anterior one-half of HL, laterally oriented. Anus adjacent to urogenital papilla, shifting ontogenetically from vertical through posterior to anterior margin of opercle. Urogenital papilla not developed in specimens under 132.8 mm LEA. Branchial membranes joined at isthmus.
Scales cycloid and small, extending from posterior most part of head to vertical through tip of caudal filament, present on mid-dorsal region of body. Scales above lateral line at vertical through end of pectoral fin 8(1), 9(1), 10*(9), 11(10), or 12(4). Anterior most perforated lateral-line scales along vertical through pectoral-fin origin. Lateral-line scales to vertical through base of last anal-fin ray 104(1), 106(1), 107(1), 108(1), 109(1), 110(2), 112(2), 113(3), 116(1), 117(1), 119*(3), 120(2), 121(1), 122(2), 124(1), 126(1), or 129(2). Pectoral-fin rays ii,14(4), ii,15*(7), ii,16(12), or ii,17(2). Distal pectoral-fin margin straight. Total anal-fin rays 185(1), 189(1), 190(1), 191(2), 192(1), 193(1), 194(1), 197(1), 199(1), 202(3), 203(2), 205(1), 207(3), 208(1), 212(2), 217(1), 219(1), 225*(1). Anal-fin origin along vertical through pectoral-fin insertion or slightly posterior. Distal margin of anal fin slightly convex. First unbranched anal-fin rays tiny, subsequent rays progressively increasing in size toward first branched rays. Branched anal-fin rays of nearly the same length except for posterior most rays that progressively decrease in length.
Relevant osteological features. Premaxillary teeth 21(1), 23(3), 24(1), 25(1), or 27(1) arranged in three (4), or four (3) rows. Dentary teeth 11(2), 13(1), 14(1), or 16(3) arranged in single (3), or two (4) rows. Endopterygoid teeth four (1), five (2), seven (3), or eight (1). Upper pharyngeal teeth eight (1), nine (32), or 10(4). Lower pharyngeal teeth nine (4), 10(2), or 11(1). Precaudal vertebrae 13(5), 14(1), or 15(1). Transitional vertebrae four (7). Pleural ribs five (2), or six (5). Displaced hemal spines two (1), or three (6).
Coloration in alcohol. Body ground coloration cream. Body with two layers of chromatophores. Outer layer covered by melanophores gradually more spaced ventrally. Lateral-line stripe, and inferior midlateral stripe absent. Superior midlateral stripe present or absent. Inner layer of pigmentation formed by multiple, small bars of dark chromatophores situated between the musculature associated with anal-fin pterygiophores (inclinatores anales). Dark individual bars in combination forming anal-fin base stripe. Head covered by dark chromatophores, more concentrated on dorsal region gradually more spaced ventrally. Pectoral and anal fins hyaline with scattered dark chromatophores overlying fin rays.
Geographical distribution. Eigenmannia wazowskii is known only from the rio Negro basin, Amazonas, Brazil (Fig. 3).
Etymology. The epithet “wazowskii” is in reference to Mike Wazowski, a fictional character from Disney/Pixar franchise Monsters Inc, that also has a large eye. To be treated in the genitive case, male.
Conservation status. Eigenmannia wazowskii apparently does not match any of the extinction risk categories given by the International Union for Conservation of Nature (IUCN). The species possesses a relatively broad distribution, being widespread in the rio Negro basin. Therefore, according to the currently available data, and using the criteria of the IUCN Standards and Petitions Subcommittee (IUCN, 2024), we propose that the species should be classified as Least Concern (LC).
Phylogenetic inference. The phylogenetic relationships and genetic distinctiveness of the new species and its congeners were investigated by an ML analysis. The best fit of nucleotide substitution estimated for the data was TN + F + I + G4. The phylogenetic reconstruction recovered E. macrops as a non-monophyletic species in which the two recovered lineages are successive sister groups of all Eigenmannia species. In turn, E. microstoma was recovered as the sister group of all other Eigenmannia species.
Eigenmannia wazowskii was recovered as the sister group of E. macuxi,and this clade is the sister group of a clade that includes E. besouro, E. catira, E. dutrai, E. vicentespelaea, E. virescens, Eigenmannia sp. “Barima”, Eigenmannia sp. “Maroni”, Eigenmannia sp. “Paraíba do Sul”, Eigenmannia sp. “Orinoco”, Eigenmannia sp. “Peru KR491591”, and Eigenmannia sp. “Purus”.
The Eigenmannia humboldtii species group was recovered as the sister clade of the lineage including E. guairaca, E. loretana, E. trilineata, Eigenmannia sp. “Peru KF533346–47”, and Eigenmannia sp. “unknown locality NC004701”. The trans-Andean Eigenmannia species was recovered as a monophyletic group being the sister group of all other Eigenmannia clades, except E. macrops and E. microstoma.
Molecular species delimitation. The ASAP lowest score recovered was 5.0, indicating the better partition, and recognizing 29 MOTU’s. In turn, PTP and bPTP results estimated respectively 27 and 41 MOTU’s (Fig. 4). ASAP and PTP analyses recovered E. wazowskii as a unique MOTU, whereas the bPTP estimated three MOTU’s in E. wazowskii. The overall mean genetic interspecific distances was 12.1±1.1%, with genetic distance between E. wazowskii and other lineages ranging from 8.7% with E. catira to 17.3% with E. loretana (Tab. S1).
FIGURE 4| Maximum likelihood tree of Eigenmannia using cytochrome c oxidase subunit I (COI; 123 sequences with 652 bp) showing the results of the molecular delimitations methods Assemble Species by Automatic Partitioning (ASAP), Poisson tree processes (PTP), and Bayesian Poisson tree processes (bPTP) for molecular operational taxonomical units (MOTUs). MOTUs are represented by black rectangles. Numbers at the bottom of branches represent bootstrap support.
Discussion
Inconsistences between molecular species delimitation analysis. Molecular analyses for species delimitation have been increasingly used in descriptions of Neotropical fish species (e.g., Boaretto et al., 2024; Martins et al., 2024). In the present study, two of the three analyses employed, ASAP and PTP, indicated a single MOTU for Eigenmannia wazowskii, corroborating the morphological delimitation of the species proposed in the diagnosis. In turn, bPTP recovered three MOTUs for this species. However, it is important to notice that this analysis also recovered four MOTUs for E. guairaca and seven MOTUs for E. magoi, evidencing a tendency to overestimate the number of species. In turn, ASAP and bPTP recovered E. dutrai, E. virescens,and Eigenmannia sp. “Paraíba do Sul” as independent MOTU’s, whereas the PTP suggested that these names belong to a single MOTU. Peixoto et al. (2020) did not provide a straight comparison between these two species in the description of E. dutrai, however, they presented an identification key in which they differed E. virescens from all other congeners in the Paraná basin by the absence of the superior midlateral dark stripe on flanks. Therefore, it is possible that the PTP is underestimating the number of species for this clade or revealing taxonomic uncertainties between these species. In turn, the ASAP seems to be the best analysis to be applied to species delimitation in Eigenmannia, once it recovered about the same species identified by morphology.
Phylogenetic implications of the presence of large eyes. Groups of species have been historically proposed for Eigenmannia in order to help identify them (e.g., Peixoto et al., 2015; Waltz, Albert, 2018a). One of them, the Eigenmannia macrops species-group, was proposed by Albert (2001) to allocate E. macrops and an undescribed species from Mamirauá Ecological Reserve. Later, Waltz, Albert (2018a,b) diagnosed this group, including only E. macrops, by having the body fairly laterally compressed, translucent white/yellow in life, longitudinal stripes absent, eye large (greater than or equal to snout length), and long caudal filament (half of body length without head). Peixoto, Ohara (2019), however, argued that there is no need to propose a monotypic species group, a decision followed by Dutra et al. (2021). Peixoto, Ohara (2019) also argued that the characters proposed by Waltz, Albert (2018a,b) are generalized features in Eigenmannia except for the large eye and long caudal filament. It is important to notice, however, that E. macrops has not the largest eye of the genus, which is of E. macuxi (22.1–32.1% of HL), followed by E. matintapereira (20.0–31.1% of HL), and then E. macrops (21.2–30.7% of HL), E. wazowskii (22.0–29.3% of HL), and E. waiwai (22.6–28.8% of HL) (see Tab. 3).The informativeness of the eye size has never been investigated in a phylogenetic context. However, considering the presence of large eye in non-related species, such as in E. macrops and members of E. trilineta sensu Dutra et al. (2021), it seems that its presence evolved independently at least two times in Eigenmannia. Additionally, all species delimitation analyses in the present study recovered the two samples of E. macrops as independent lineages, highlighting the existence of a hidden diversity under this name, which could support the usage of a species group for this clade as suggested by Waltz, Albert (2018a,b). However, a detailed taxonomic study of this species is required before these changes.
TABLE 3 | Morphometrics of eye diameter, as percent of HL, of valid species of Eigenmannia. Table based on compiled data from Peixoto et al. (2015, 2020), Peixoto, Wosiacki (2016), Campos-da-Paz, Queiroz (2017), Dutra et al. (2017, 2018, 2022, 2024), Peixoto, Waltz (2017), Peixoto, Ohara (2019), Herrera-Collazos et al. (2020), and Cardoso, Dutra (2023). An asterisk indicates species that data were collected straight in specimens. Species are arranged by decreasing order of maximum values.
| Min | Max | Mean |
Eigenmannia macuxi | 22.1 | 32.1 | 26.1 |
Eigenmannia matintapereira | 20.0 | 31.1 | 25.1 |
Eigenmannia macrops* | 21.2 | 30.7 | 25.2 |
Eigenmannia wazowskii* | 22.0 | 29.3 | 25.6 |
Eigenmannia waiwai | 22.6 | 28.8 | 25.8 |
Eigenmannia microstoma | 15.2 | 25.7 | 20.2 |
Eigenmannia bumba | 21.3 | 25.4 | 23.8 |
Eigenmannia besouro | 16.9 | 25.1 | 20.5 |
Eigenmannia magoi | 18.0 | 24.9 | 20.3 |
Eigenmannia camposi | 15.5 | 24.8 | 20.2 |
Eigenmannia virescens* | 15.5 | 24.8 | 20.2 |
Eigenmannia robsoni | 17.2 | 24.5 | 20.6 |
Eigenmannia catira | 14.5 | 24.5 | 19.8 |
Eigenmannia zenuensis | 13.5 | 24.4 | 19.4 |
Eigenmannia limbata* | 13.1 | 24.3 | 19.7 |
Eigenmannia oradens | 19.4 | 24.1 | 21.9 |
Eigenmannia loretana | 15.7 | 23.9 | 19.8 |
Eigenmannia sirius | 17.2 | 23.8 | 20.5 |
Eigenmannia muirapinima | 13.8 | 23.8 | 18.7 |
Eigenmannia meeki | 17.4 | 22.7 | 20.1 |
Eigenmannia sayona | 17.3 | 22.4 | 20.1 |
Eigenmannia trilineata | 15.3 | 21.6 | 17.9 |
Eigenmannia cacuria | 17.5 | 21.1 | 19.0 |
Eigenmannia humboldtii* | 14.1 | 20.8 | 17.6 |
Eigenmannia dutrai | 14.4 | 20.3 | 17.3 |
Eigenmannia desantanai | 14.5 | 19.6 | 17.0 |
Eigenmannia antonioi | 12.5 | 19.6 | 16.5 |
Eigenmannia nigra* | 15.4 | 19.4 | 17.7 |
Eigenmannia pavulagem | 12.3 | 19.3 | 15.8 |
Eigenmannia guairaca | 11.4 | 15.0 | 13.3 |
Eigenmannia vicentespelaea | 5.0 | 18.0 | 9.6 |
Eigenmannia correntes | 10.6 | 13.3 | 12.0 |
Eigenmannia diversity in the rio Negro basin. Beltrão et al. (2019) listed the occurrence of seven species of Eigenmannia occurring in the rio Negro basin (including rio Branco): E. humboldtii, E. limbata, E. macrops, E. matintapereira, E. nigra, E. trilineata and E. virescens. During the present study, we examined Eigenmannia specimens from the rio Negro cited in previous studies (e.g., Beltrão et al., 2019) to update their identifications. The specimens initially identified as E. humboldtii (MZUSP 29953) and E. limbata (INPA 16112 and 20159) corresponds to E. nigra. Nevertheless, the occurrence of E. limbata is confirmed in the basin by the lot MZUSP 93431. The specimens previously assigned as E. macrops (INPA 30756 and 33023) and E. trilineata (INPA 30020 and 37801) are tentatively identified here as E. aff. virescens. However, the occurrence of E. macrops is confirmed in the basin by the lots: LBP 35673, MZUEL 15436, and MZUSP 130863. In turn, specimens previously identified as E. virescens (INPA 33028) correspond to E. aff. trilineata, however this voucher as indicated by Beltrão et al. (2019) is not from rio Negro basin, but from the rio Solimões.The occurrence of this morphotype is confirmed by the lots INPA 6494, 51599, and 59103. Considering the revised identifications of Eigenmannia specimens from rio Negro, in addition to species listed by Dutra et al. (2024) in the rio Branco basin as well as the species described herein, we recognize the occurrence of the following eight species in the area: E. limbata, E. macrops, E. macuxi, E. matintapereira, E. nigra, E. aff. trilineata, E. aff. virescens, and E. wazowskii. It is important to notice that an exhaustive study on the specimens tentatively identified as E. aff. trilineata and E. aff. virescens could reveal an even greater diversity in the basin.
Comparative material. In addition to the comparative material listed in Dutra et al. (2014, 2017, 2018, 2021, 2022, 2024) and Cardoso, Dutra (2023), the following material were examined: Eigenmannia humboldtii: FMNH 56812, 3 xr, 186.2–208.6 mm LEA, Puerto del Río. IAvH-P 6788, 1 xr, 319.7 mm LEA, IAvH-P 6800, 1 xr, 278.5 mm LEA, IAvH-P 6806, 1 cs, 205.7 mm LEA, río Atrato. IAvH-P 6794, 1 xr, 330.0 mm LEA, IAvH-P 6798, 1, 248.9 mm LEA, río Cabi. IAvH-P 7024, 1 xr, 199.8 mm LEA, río Atrato, Quebrada Baulata. IAvH-P 7415, 15 (1 xr), 206.8–331.6 mm LEA, Cienaga Unguía y sus caños. IAvH-P 7822, 1 xr, 312.0 mm LEA, IAvH-P 7823, 1 xr, 278.6 mm LEA, IAvH-P 7824, 1, 296.5 mm LEA, río Magdalena. NRM 27741, 1, 294.1 mm LEA, canõ Ponelaolla and mouth of río Guaguandó. Eigenmannia limbata: MNRJ 1186, holotype of Sternopygus limbatus, 324.0 mm LEA, Amazonas, Brazil. INHS 36854, 5, 196.7–240.3 mm LEA, tributary of río Nanay. INHS 44128, 3, 170.5–195.8 mm LEA, Mazan. INHS 54993, 1, 130.2 mm LEA, río Napo. INPA 18681, 1, 192.8 mm LEA, INPA 18683, 2, 218.5–228.5 mm LEA, Paraná Maiana. INPA 28510, 3 (1 cs), 185.9–224.2 mm LEA, rio Caeté. INPA 29773, 1 xr, 170.4 mm LEA, RDS Uakari. MCP 28641, 1, 327.0 mm LEA, MCP 28642, 1, 275.0 mm LEA, Lago Pirapora. MCP 47521, 1, 143.0 mm LEA, Igarapé Marizinho. MZUSP 24594, 1, 211.3 mm LEA, mouth of Pauiní. MZUSP 26499, 1, 116.6 mm LEA, Pucallpa, río Ucayali basin. MZUSP 73475, 1, 155.8 mm LEA, Cachoeira Teotônio. MZUSP 93431, 3, 250.5–332 mm LEA, rio Tiquié. USNM 228861, 12, 129.0–273.0 mm LEA, laguna on south of Isla Isabela. USNM 305519, 4, 148.6–165.0 mm LEA, río Curiraba. USNM 305793, 2, 138.5–211.5 mm LEA, USNM 305802, 8, 122.6–250.5 mm LEA, río Matos. Eigenmannia loretana: IIAP 1158, 3 (not measured), Loreto, Peru. Eigenmannia macrops: LBP 35673, 6, 50.7–95.3 mm LEA, rio Negro. MZUEL 15436, 2, 97.8–93.5 mm LEA, Parque Nacional de Anavilhanas. MZUSP 118455, 3, 59.2–74.0 mm LEA, río Ampiyacu. MZUSP 127627, 90 (7 cs), 59.2–143.1 mm LEA, rio Amazonas near Santarém. MZUSP 130863, 14, 56.9–81.3 mm LEA, rio Jauaperi. Eigenmannia nigra: AMNH 58642, 3 xr paratypes, 235.4–296.5 mm LEA, Venezuela, Amazonas, Caño Urami. ANSP 162130, 3 paratypes, 243.0–265.0 mm LEA, Venezuela, río Casiquiare. BMNH 1998.3.17.1-15, 4, 169.0–187.8 mm LEA, Paraná Apara. CAS 54387, 4 (1 cs), 139.2–166.9 mm LEA, CAS 54518, 1, 130.3mm LEA, río Orinoco bifurcation, Tamatama rock. INHS 36854, 5, 196.7–240.3 mm LEA, tributary of río Nanay. INHS 37628, 4, 100.2–121.1 mm LEA, río Nanay at Pampa Chica. INHS 37828, 1, 214.7 mm LEA, río Napo at mouth of río Mazan. INHS 39295, 1, 114.9 mm LEA, Mayuruna. INHS 43898, 1, 139.7 mm LEA, Quebrada Shushuna, 03°49’47.6”S 73°20’14.2”W. INPA 15813, 12, 148.4–222.4 mm LEA, Lago Tefé. INPA 16112, 1, 266.0 mm LEA, Lago do Aleixo. INPA 20159, 3, 222.0–315.0 mm LEA, Paraná do Xiborena. MZUSP 29953, 4 (not measured), rio Uraricoera. MPEG 1091, 3, 128.8–146.6 mm LEA, MPEG 2425, 8, 171.4–295.6 mm LEA, MPEG 2430, 8 (1 cs), 154.0–262.4 mm LEA, MPEG 2509, 3, 250.0–280.6 mm LEA, MPEG 2510, 15 (1 cs), 180.8–293.0 mm LEA, MPEG 2810, 1, 273.1 mm LEA, rio Goiapi, Marajó Island. MPEG 6484, 1 cs, 179.3 mm LEA, Igarapé Tijucaquara. MPEG 8717, 1, 297.1 mm LEA, rio Xingu basin. MPEG 9537, 2, 179.0–182.0 mm LEA, Igarapé Arrainha. MPEG 15522, 1, 207.8 mm LEA, Igarapé Curuá. MPEG 20025, 1, 176.0 mm LEA, Igarapé Anajazinho, MPEG 20512, 1, 194.6 mm LEA, rio Castanha. MPEG 22749, 1, 120.4 mm LEA, Ressaca do Pagão. MPEG 24356, 2, 210.3–259.0 mm LEA, rio Maicuru. MZUSP 89434, 4, 128.3–224.0 mm LEA, rio Palmital. MZUSP 91646, 1, 280.3 mm LEA, rio Uaupés. USNM 260240, 5 (1 cs), 192.2–225.2 mm LEA, río Apure. Eigenmannia aff. trilineata: INPA 6494, 4, 56.2–84.1 mm LEA, rio Negro. INPA 33028, 6, 42.1–83.4 mm LEA, Ilha da Paciência. INPA 51599, 3, 86.1–93.2 mm LEA, rio Preto. INPA 59103, 2, 72–81.5 mm LEA, lago Catalão. Eigenmannia virescens: LBP 4335, 12, 67.8–166.8 mm LEA, Córrego do Onça. LBP 13458, 19, 118.5–137.3 mm LEA, rio Cuiabá. MCP 12474, 1, 190.2 mm LEA, rio Uruguai. MCP 13416, 5, 146.4–180.4 mm LEA, rio do Peixe em Volta. MCP 19330, 1, 145.8 mm LEA, rio Uruguai. MCP 21139, 3, 160.0–238.0 mm LEA, rio das Antas. MCP 26819, 1, 213.0 mm LEA, rio Ibicuí Mirim. Eigenmannia aff. virescens: INPA 30020, 2, 64.2–81.4 mm LEA, rio Preto da Eva. INPA 30756, 1, 59.0 mm LEA, rio Branco. INPA 33023, 1, 72.2 mm LEA, Ilha da Paciência, Manaus. INPA 37801, 3, 67.8–86.3 mm LEA, rio Darahá. LBP 6900, 2, 75.4–100.0 mm LEA, rio Negro. LBP 6943, 3, 78.0–118.8 mm LEA, Igarapé Puranga. MZUSP 130715, 5 (1 cs), 129.7–161.1 mm LEA, rio Jauaperi.
Acknowledgments
Authors are thankful to the following individuals and institutions for access to material under their care: Scott Schaefer and Ryan Thoni (AMNH), Mark Sabaj and Maringeles Arce (ANSP); James Maclaine (BMNH); David Catania (CAS); Francisco Villa (CZUT); Caleb McMahan and Susan Mochel (FMNH); Carlos do Nascimiento (IAvH); Ivan Mojica (ICN-MHN); Chris Taylor (INHS); Lucia Rapp Py-Daniel, Lindalva Serrão and Renildo de Oliveira (INPA); Cláudio Oliveira (LBP); Leandro Sousa (LIA); Carlos Lucena and Roberto Reis (MCP); Karsten Hartel (MCZ); Raphael Covain (MHNG); Cristiano Moreira, Marcelo Britto and Paulo Buckup (MNRJ), Wolmar Wosiacki and Izaura Maschio (MPEG); Tiago Carvalho (MPUJ); Max Hidalgo (MUSM); Fernando Jerep, José Birindelli, Edson Santana (MZUEL); Aléssio Datovo, Murilo Pastana, Osvaldo Oyakawa and Michel Gianeti (MZUSP); Sven Kullander (NRM); Carla Pavanelli and Marli Campos (NUP); Andre Netto-Ferreira and Luiz Malabarba (UFRGS); Diane Pitassy, Linne Parenti, Kris Murphy and Erika Wilbur (USNM); and Flavio Lima (ZUEC) for the loan of specimens and assistance during visits to their institutions. James García-Ayala (UNESP) kindly provided photos of Eigenmannia species stored at Instituto de Investigaciones de la Amazonía Peruana (IIAP), Iquitos, Peru.
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Authors
Maria Isabela Moreira Uliam1, Helena Paulino Amorim Ribeiro1 and Guilherme Moreira Dutra2
[1] Universidade do Estado de Minas Gerais, Unidade Acadêmica Passos, Avenida Juca Stockler, 1130, 37900-106 Passos, MG, Brazil. (MIMU) isabela.uliam@gmail.com, (HPAR) helenaribs12@gmail.com.
[2] Departamento de Biologia Estrutural e Funcional, Instituto de Biociências, Universidade Estadual Paulista, Rua Prof. Dr. Antônio C. W. Zanin, 250, 18618-689 Botucatu, SP, Brazil. (GMD) guilhermedutr@yahoo.com.br (corresponding author).
Authors’ Contribution 
Maria Isabela Moreira Uliam: Data curation, Formal analysis, Investigation, Methodology, Writing-original draft, Writing-review and editing.
Helena Paulino Amorim Ribeiro: Data curation, Formal analysis, Investigation, Methodology, Writing-original draft, Writing-review and editing.
Guilherme Moreira Dutra: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Writing-original draft, Writing-review and editing.
Ethical Statement
Not applicable.
Competing Interests
The author declares no competing interests.
Data availability statement
The authors confirm that the data supporting the findings of this study are available within the article.
Funding
Authors were supported by the Programa Institucional de Apoio à Pesquisa (PAPq/UEMG 16/2023 to MIMU), the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP #2018/09445–9 to GMD), Conselho Nacional de Desenvolvimento Científico e Tecnológico (grant #153825/2024–3 to GMD). This contribution was also supported by the Diversity and Evolution of the Gymnotiformes Project, FAPESP/Smithsonian (proc. #2016/19075–9), and INCT – Biodiversidade e uso sustentável de Peixes Neotropicais (proc. #405706/2022–7).
How to cite this article
Uliam MIM, Ribeiro HPA, Dutra GM. Description of a new species of glass knifefish genus Eigenmannia (Gymnotiformes: Sternopygidae) from the rio Negro basin, Brazil. Neotrop Ichthyol. 2025; 23(3):e250004. https://doi.org/10.1590/1982-0224-2025-0004
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Diversity and Distributions Published by SBI
Accepted August 18, 2025
Submitted January 10, 2025
Epub November 14, 2025