Eigenmannia oradens, Dutra & Peixoto & Santana & Wosiacki, 2018

Dutra, Guilherme Moreira, Peixoto, Luiz Antônio Wanderley, Santana, Carlos David De & Wosiacki, Wolmar Benjamin, 2018, A new species of Eigenmannia Jordan & Evermann (Teleostei: Gymnotiformes: Sternopygidae) from Río Ventuari, Venezuela, Zootaxa 4422 (1), pp. 132-140 : 133-138

Eigenmannia oradens , new species

Figs. 1– 3 , Table 1

Holotype. ANSP 190768, xr, 121.6 mm LEA, Venezuela, Amazonas, Río Ventuari at Raudales Chipirito, 88.5 Km east of San Fernando de Atabapo, 04°04’6”N 66°54’13”W, 0 1 April 2010, M. Sabaj-Pérez, N.K. Lujan, D.C. Werneke, T. Carvalho, S. Meza V., A. Luna & O. Santaella.

Paratypes. ANSP 190912 , 2 xr, 62.6–101.1 mm LEA, Venezuela, Amazonas, Río Ventuari ca. 20 airmiles NE of confluence with Río Orinoco , near ornamental fish market in river, 04°04’32”N 66°53’34”W, 0 3 April 2005, N.K. Lujan, M. Arce, E.L. Richmond, M.P. Grant & T.E. Wesley . ANSP 203212, 1xr, 76.7 mm LEA, collected with the holotype, MPEG 35287, 1xr+1CS, 94.7–111.1 mm LEA, collected with the holotype. MZUSP 122802, 1MS, 102.3 mm LEA, collected with the holotype. USNM 440377, 1xr, 91.4 mm LEA, collected with the holotype.

Diagnosis. Eigenmannia oradens differs from all congeners by presence of bony dorsolateral flange of dentary which also anchors numerous teeth along its extension (versus dorsolateral flange absent and teeth are attached only in dentary rim), and first premaxillary teeth row mobile, teeth attached to anteroventral margin of premaxilla (versus first premaxillary teeth row immobile, teeth completely attached to ventral surface of premaxilla). It is further distinguished from remain congeners, except E. besouro Peixoto & Wosiacki, 2016 , E. correntes Camposda-Paz & Queiroz, 2017 , E. meeki Dutra, de Santana & Wosiacki, 2017 , E. vicentespelaea Triques, 1996 , E. virescens Valenciennes, 1836 , and E. waiwai Peixoto, Dutra & Wosiacki, 2015 by the subterminal mouth (versus terminal: Fig. 2 ). The new species is diagnosed from E. besouro , E. correntes , E. meeki , E. vicentespelaea , and E. virescens by having 38–42 teeth on premaxilla (versus 18–29 in E. besouro , 17–20 in E. correntes , 30–35 in E. meeki , 25–26 in E. vicentespelaea , and 22 in E. virescens ). It is distinguished from E. besouro , E. correntes , E. meeki , E. virescens , and E. waiwai by the coronomeckelian bone corresponding to 45% of length of Meckel’s cartilage (versus 20% of length of Meckel’s cartilage in E. correntes , E. meeki , E. virescens and E. waiwai and 30% of length of Meckel’s cartilage in E. besouro ).

Eigenmannia oradens also differs from E. meeki , E. vicentespelaea , and E. waiwai by having 99–107 scales along lateral line until the end of anal fin (versus 140–168 in E. meeki , 110–125 in E. vicentespelaea , and 111–128 in E. waiwai ). It is further distinguished from E. besouro , E. correntes , E. vicentespelaea and E. waiwai by absence of superior midlateral stripe (versus presence). The new species is additionally diagnosed from E. meeki , E. virescens , and E. waiwai by depth of posterodorsal expansion on infraorbitals 1+2 approximately equal to total length of infraorbitals 1+2 (versus less than 50% of the length of infraorbitals 1+2). Eigenmannia oradens also differs from E. besouro , E. correntes and E. waiwai by having ii, 16–17 pectoral fin rays (versus ii, 13–14 in E. besouro , ii, 11–12 in E. correntes , and ii, 13–15 in E. waiwai ). It is distinguished from E. correntes and E. meeki by having 31–38 dentary teeth (versus 16–18 and 20–23 respectively), and 164–192 anal-fin rays (versus 211–240). It also differs from E. virescens by presence of narrow stripe on lateral line (versus absence). Eigenmannia oradens is diagnosed from E. waiwai by having 14 precaudal vertebrae (versus 12 or 13).

Description. Body shape and pigmentation in Figs. 1 and 2 . Morphometric data for examined specimens in Table 1. Largest examined specimen 121.6 mm LEA. Body elongate, distinctly compressed laterally. Greatest body depth at vertical through distal margin of pectoral fin. Dorsal profile of body convex to straight. Ventral profile slightly convex. Caudal filament elongate.

Head compressed, greatest width in opercular region and greatest depth at nape ( Fig. 2 ). Dorsal profile of head convex. Ventral profile of head slightly straight. Snout subconical in lateral view. Mouth subterminal. Premaxillary teeth 38(1) or 42 (1) arranged in five (1) or six (1) rows. First premaxillary teeth row mobile, teeth attached only to anteroventral margin of premaxilla. Maxilla slender with short, hook-shaped anterodorsal process. Posterior margin of maxilla reaching posterior margins of first and second infraorbitals. Dentary teeth 31(1) or 38(1) arranged in three (2) rows. Dentary teeth attached in bony dorsolateral flange of dentary ( Fig. 3 ). Coronomeckelian bone corresponds to 45% of length of Meckel’s cartilage. Endopterygoid teeth 10(1) arranged in single row. Mouth rictus extending posteriorly to vertical between nares or on posterior nostril. Anterior naris tube-like, closer to snout tip than to anterior margin of eye. Posterior naris rounded, without tube; near midpoint between anterior naris and anterior margin of eye. Eye small, circular, completely covered by thin membrane, on anterior one-half of HL and laterally oriented. Antorbital and infraorbitals 1 to 4 enlarged, partially cylindrical with slender osseous arches. Fifth and sixth infraorbitals slender and tubular. Depth of posterodorsal expansion on infraorbitals 1+2 equals total length of infraorbitals 1+2. Gill opening limited to posterior margin of opercle and extending above and below pectoral-fin base. Gill rakers tiny and fleshy. Seven (1) gill rakers on first ceratobranchial. Six (2) gill rakers on first infrapharyngobranchial. Upper pharyngeal plate with 10(1) teeth. Lower pharyngeal plate with nine (1) teeth.

Branchial membranes joined at isthmus. Branchiostegal rays five (1). First and second branchiostegal rays narrow. Third to fifth branchiostegal rays spatulate. First to fourth branchiostegal rays attached to anterior ceratohyal. Fifth branchiostegal ray attached to posterior ceratohyal.

Anus and urogenital papilla adjacent. Position of anus and urogenital papilla shifting through ontogeny from vertical through posterior margin of eye to vertical through middle of eye.

Scales small, cycloid, extending from immediately posterior of head to tip of caudal filament. Scales present on mid-dorsal region of body. Scales above lateral line at midbody eight(4), nine(1), ten*(2), or 11(1). Lateral-line scales to vertical through anal-fin terminus 99(1), 100(3), 104(1), 105(2), or 107*(1).

Pectoral-fin rays ii,16(7) or ii,17*(1). Three proximal radials. Distal pectoral-fin margin straight. Total anal-fin rays 164(1), 173(1), 177(1), 178*(2), 182(1), or 192(1). Anal-fin origin below pectoral-fin insertion. Distal margin of anal fin straight. First unbranched rays tiny; rays progressively increasing in size to first branched rays. Branched rays all of nearly equal length, except for posterior most rays that progressively decrease in size.

Precaudal vertebrae 14*(7). Transitional vertebrae three (3) or four* (4). Vertebrae to end of anal fin 57(1), 59(2), 60(2) or 61(1). Pleural ribs six*(3) or seven (7). Displaced hemal spines four* (7).

Coloration in alcohol. Body ground coloration cream. Body densely covered by dark chromatophores gradually more spaced ventrally. Chromatophores more concentrated on perforated scales forming lateral line stripe ( Fig. 1 ). Second layer of pigmentation formed by multiple, small bars of dark chromatophores situated between musculature associated with anal-fin pterygiophores. Dark individual bars in combination form two stripes-like patterns. Inferior midlaterial stripe approximately as wide as orbital diameter. Anal-fin base stripe approximately as wide as orbital diameter.

Head densely covered by dark chromatophores gradually more spaced ventrally. Lips distinctly darker than proximate areas. Pectoral and anal fins hyaline with scattered dark chromatophores overlying fin rays.

Distribution. Eigenmannia oradens is only known from its type locality in the Río Ventuari, Río Orinoco basin, Estado Amazonas in Venezuela ( Fig. 4 ).

Etymology. The specific epithet, oradens , is from the Latin ora, meaning edge, and dens, meaning tooth, in allusion to the presence of a bony dorsolateral flange on the dentary in which teeth are attached. An adjective.

Remarks. Eigenmannia oradens can be diagnosed among congeners by a remarkable arrangement of the oral dentition. In the premaxilla the anterobasal margin of the first tooth row is attached to it surface. Consequently, this arrangement, gives mobility freedom to the teeth, which can reach 90 degrees from the vertical. This type of attachment is also known in species of Archolaemus ( Vari et al., 2012) . Broadly, the premaxilla attachment in Archolaemus and E. oradens can be included in the Type 3 of Fink (1981) [“...a tooth attachment mode which acts as a hinge, with its axis of rotation being the anterior tooth attachment site”; pg. 176]. In contrast, the first tooth row is completely attached to the premaxilla in Sternopygidae , Type 2 of Fink (1981). The dentary of E. oradens is characterized by a bony dorsolateral flange, which anchors numerous teeth along its extension ( Fig. 3 ). Such condition also occurs in Archolaemus , D. guchereauae , and Japigny . And according to the current hypotheses of phylogenetic relationships it is considered a convergence among the four taxa (e.g., Tagliacollo et al., 2016). As noted in the diagnosis for the new species, the number of teeth rows of premaxilla and dentary have a large variation across Eigenmannia and can be explored as source of taxonomic characters. The description of E. oradens corroborates with previous studies that used teeth arrangement and attachment as a valuable source of taxonomic information at different hierarchical levels (e.g., Vari et al., 2012; Peixoto et al., 2015; Peixoto & Wosiacki, 2016; Campos-da-Paz & Queiroz, 2017; Dutra et al., 2017; Peixoto & Waltz, 2017).

Comparative material examined. Archolaemus blax : INPA 6424, 20+4CS, 118–270mm TL, Rio Tocantins above Tucuruí Dam, Brazil. MNRJ 12158, 18+4CS of 93, 90.0–382.0 mm TL, Rio Bezerra, Rio Tocantins basin, Brazil. Archolaemus ferreirai : INPA 6422, 8+4CS paratypes, 131.0–269.0 mm TL, Rio Mucajaí, Rio Branco basin, Brazil. INPA 36379, 20+1CS paratype, 119.0–342.0 mm TL, Rio Mucajaí, Rio Branco basin, Brazil. Archolaemus janeae : INPA 36380, 14+2CS paratypes, 136.0–225.0 mm TL, Rio Iriri, Rio Xingu basin, Brazil. Archolaemus luciae : INPA 20964, 8+4CS paratypes, 106.0–200.0 mm TL, Rio Trombetas, Brazil. Archolaemus orientalis : FMNH 94418, 1CS of 3 paratype, Rio São Francisco, Brazil. MPEG 21508, holotype, 156.0 mm TL, Rio Paracatu, Rio São Francisco basin, Brazil. MPEG 21509, 1MS paratype, 150.0 mm TL, Rio Paracatu, Rio São Francisco basin, Brazil. Archolaemus santosi : INPA 36382, 6+3CS paratypes, 73.0–212.0 mm TL, Rio Jamari, Rio Madeira basin, Brazil. Distocyclus conirostris : INPA 11482, 7+3CS of 32, 100.2–197.0 mm LEA, Rio Purus, Brazil. INPA 28879, 2CS of 19, 108.7–165.0 mm LEA, Rio Negro, Brazil. INPA 28915, 2CS of 11, 108.1– 130.5 mm LEA, Rio Negro, Brazil. INPA 34018, 8+1CS, 132.0– 174.5 mm LEA, Praia Grande above community of Carapanã, Rio Purus basin, Brazil. MPEG 20023, 2+1CS, 120.9–196.4 mm LEA, Rio Arari, Ilha do Marajó, Brazil. MPEG 20024, 2+1CS, 149.1–181.0 mm LEA, Rio Arari, Ilha do Marajó, Brazil. MZUSP 6982, 2+1CS, 156.2–166.0 mm LEA, Rio Madeira, Brazil. Distocyclus guchereauae : MNHN 2003-0013, 1, 222.0 mm TL, Maroni drainage, French Guiana. MNHN 2003-0014, 1, 232.0 mm TL, Maroni drainage, French Guiana. MNHN 2003-0018, 2, 322.0–321.0 mm TL, Maroni drainage, French Guiana. Eigenmannia antonioi : MPEG 10182, 6+1CS paratypes, 77.0– 118.3 mm LEA, Rio Anapu, Brazil. Eigenmannia besouro : MZUSP 57890, holotype, 91.9 mm LEA, Rio Grande, São Desidério, Brazil; MZUSP 119104, 5+1CS, paratypes, 69.6–106.1 mm LEA. MZUSP 83792, 6+1CS, paratypes, 55.8–68.8 mm LEA, Rio Preto, Brazil. Eigenmannia desantanai : NUP 3470, 10+1CS paratypes, 119.8– 142.8 mm LEA, Rio Cuiabá, Brazil. Eigenmannia guairaca : NUP 6467, 8+2CS paratypes, 81.4–135.8 mm LEA, Riacho Água do Ó, Brazil. Eigenmannia humboldtii : IAvH-P 6788, 1, 316.7 mm LEA, Río Atrato, Colombia. IAvH-P 6794, 1, 330.0 mm LEA, Río Atrato, Colombia. IAvH-P 6800, 288.3 mm LEA, Río Atrato, Colombia. IAvH-P 6806, 1CS, 205.7 mm LEA, Río Atrato, Colombia. IAvH-P 7024, 1, 199.8 mm LEA, Río Atrato, Colombia. IAvH-P 7415, 2, 240.9– 270.1 mm LEA, Río Atrato, Colombia. IAvH-P 7822, 1, 312.0 mm LEA, Río Magdalena, Colombia. IAvH-P 7823, 1, 264.0 mm LEA, Río Magdalena, Colombia. NRM 27741, 1, 294.1 mm LEA, Canõ Ponelaolla, Colombia. USNM 247229, 3, 134.9– 175.6 mm LEA, Río Salado, Colombia. Eigenmannia limbata : INPA 18288, 2CS, 98.0–151.0 mm LEA, Lago Mamirauá, Brazil. USNM 305802, 10+2CS, 122.6–250.5 mm LEA, Rio Matos, Bolivia. Eigenmannia macrops : BMNH 1897.8.6.1, holotype, 128.5mm LEA, Potaro River, Guyana. USNM 402684, 6, 80.1–116.8 mm LEA, Cuyuni River, Guyana. USNM 405265, 3, 56.3–107.8 mm LEA, Cuyuni River, Guyana. USNM 405266, 15+1CS, 63.3–162.9 mm LEA, Cuyuni River, Guyana. Eigenmannia matintapereira : MZUSP 109618, 3+1CS paratypes, 79.7–143.6 mm LEA, Rio Uneiuxi, Brazil. MZUSP 109695, 5+1CS paratypes, 65.7–167.7 mm LEA, Rio Urubaxi, Brazil. Eigenmannia meeki : USNM 293171, holotype, 235.7 mm LEA, Río Pucuro, Panamá. MPEG 33912, 1+1 CS, 194.6–222.0 mm LEA, Río Pucuro, Panamá. Eigenmannia microstoma : BMNH 1868.7.8.2–3, 2 syntypes, 101.1–139.3 mm LEA, Rio São Francisco basin, Brazil. ZMUC P2516 (formally ZMUC 21), 1 syntype (photo and radiograph), 162.8 mm LEA, Rio São Francisco basin, Brazil. ZMUC P2517 (formally ZMUC 23), 1 syntype, 153.8 mm LEA, Rio São Francisco basin, Brazil. ZMUC P2518 (formally ZMUC 24), 1 syntype, 176.6 mm LEA, Rio São Francisco basin, Brazil. ZMUC P2519 (formally ZMUC 25), 1 syntype, 105.1 mm LEA, Rio São Francisco basin, Brazil. ZMUC P2520 (formally ZMUC 26), 1 syntype, 101.1 mm LEA, Rio São Francisco basin, Brazil. MCP 45216, 5+1CS, 57.7–91.6 mm LEA, Rio Pandeiros, Brazil. Eigenmannia muirapinima : MPEG 21777, 1+3CS paratypes, 84.6–98.5 mm LEA, Lago Jará, Brazil. MPEG 29489, 11+2CS paratypes, 76.2–97.7 mm LEA, Igarapé Santo Antônio, Brazil. Eigenmannia nigra : ANSP 162130, 3 paratypes, 243.0–265.0 mm LEA, Río Casiquiare, Venezuela. BMNH 1998.3.17, 8 of 15, 133.0– 192.9 mm LEA, Paraná Apara, Brazil. CAS 54387, 3+1CS of 5, 139.2– 166.9 mm LEA, Río Orinoco bifurcation, Venezuela. CAS 54518, 1, 130.3 mm LEA, Río Orinoco bifurcation, Venezuela. INPA 9976, 3+1CS of 10, 149.7– 223.1 mm LEA, Paraná Apara, Brazil. INPA 15813, 12, 148.4– 222.4 mm LEA, Lago Tefé, Brazil. USNM 260240, 4+1CS of 22, 192.2– 225.2 mm LEA, main channel of Río Apure, Venezuela. Eigenmannia pavulagem : MPEG 9524, 3CS paratypes, 90.7–108.5 mm LEA, Igarapé Anuera-Grande, Brazil. MPEG 29490 paratypes, 25+2CS, 26.2–176.6 mm LEA, Igarapé Paraquequara, Brazil. Eigenmannia sayona : MZUSP 96497, holotype, 131.8 mm LEA, Río Parguaza, Cedeño, Venezuela; MZUSP 119711, paratypes, 6+2CS, 27.8-116.2 mm LEA. Eigenmannia trilineata : UFRGS 6635, 10, 58.5–143.8 mm LEA, Rio Tramandaí, Brazil. UFRGS 6790, 12, 92.8–159.1 mm LEA, Arroio Gueromana, Brazil. UFRGS 8788, 3, 114.2– 130.5 mm LEA, Rio Pardo, Brazil. UFRGS 13329, 1, 124.3 mm LEA, Arroio Corrientes, Brazil. Eigenmannia virescens : MCP 12474, 1, 190.1 mm LEA, Rio Uruguai, Brazil. MCP 13416, 5, 148.7–196.0, Rio do Peixe, Brazil. MCP 16797, 5+2CS, 143.7–182.0 mm LEA, Rio Ijuizinho, Brazil. MCP 19330, 1, 147.0 mm LEA, Rio Uruguai, Brazil. MCP 21139, 3, 157.3– 236.1 mm LEA, Rio das Antas, Brazil. MCP 26819, 1, 212.9 mm LEA, Rio Ibicui, Brazil. Eigenmannia vicentespelaea : MZUSP 83461, 3+1CS, 108.0– 164.5 mm LEA, Cave of São Vicente I, Brazil. Eigenmannia waiwai , INPA 37594, 31+2CS paratypes, 94.0– 138.1 mm LEA, Rio Mapuera, Brazil. INPA 37567, 3+1CS paratypes, 74.9–154.8 mm LEA, Cachoeira Porteira, Brazil. “ Eigenmannia ” goajira: USNM 121596, holotype, 377.0 mm LEA, Río Socuy, Venezuela. USNM 121596, 1, paratype, 335.6 mm LEA, Río Socuy, Venezuela. Japigny kirschbaum : MNHN 2008-1201, 110.9 mm TL, holotype, Mana River, French Guiana; MNHN 2000-5954, 2, 99–111 mm TL, paratypes, Maroni drainage, French Guiana. FMNH 50185, 3CS, New River drainage, head of Itabu Creek, Guyana. Rhabdolichops caviceps : INPA 20157, 8+2CS, 108.7–134.5 mm LEA, Paraná do Xiboquena, tributary of Rio Solimões, Brazil. Rhabdolichops eastwardi : INPA 12361, 2CS of 41, Lago do Prato, Rio Negro, Amazonas, Brazil. MPEG 1189, 2CS, 115.1–127.8 mm LEA, Rio Goiapi, Ilha do Marajó, Brazil. Rhabdolichops electrogrammus : INPA 28863, 8+2CS of 79, 96.8– 101.5 mm LEA, Rio Negro, Brazil. Rhabdolichops lundbergi : INPA 11406, 7+3CS of 111, 133.6– 155.6 mm LEA, Rio Coari, tributary of Rio Solimões, Brazil. Rhabdolichops nigrimans : INPA 28862, 11+2CS, 97.3–132.0 mm LEA, Rio Negro, Brazil. Rhabdolichops troscheli : MPEG 1174, 1, Rio Goiapi, Ilha do Marajó, Brazil. MPEG 2604, 9+2CS, 90.0– 94.7 mm LEA, Rio Goiapi, Ilha do Marajó, Brazil. MPEG 2803, 1CS, 222.0 mm LEA, Rio Goiapi, Ilha do Marajó, Brazil. MPEG 8482, 1CS, 170.1 mm LEA, Tomé-Açu, Pará, Brazil.

Figures

FIGURE 1. Eigenmannia oradens, ANSP 190768, 121.6 mm LEA, holotype; Venezuela, Amazonas, Río Ventuari, Río Orinoco basin.

FIGURE 2. Lateral view of head of Eigenmannia oradens, ANSP 190768, 121.6 mm LEA, holotype; Venezuela, Amazonas, Río Ventuari, Río Orinoco basin.

FIGURE 3. Schematic illustration of medial view of lower jaw of Eigenmannia oradens, MPEG 35287, 94.7 mm LEA. Abbreviations: aa, anguloarticular; dlf, dentary bony dorsolateral flange; mc, Meckel’s cartilage; cb, coronomeckelian bone; den, dentary; ra, retroarticular.

FIGURE 4. Map of the northern South America showing the type locality (white circle) of Eigenmannia oradens. The symbol represents more than one locality.