Eigenmannia desantanai, Peixoto & Dutra & Wosiacki, 2015

Peixoto, Luiz Antônio Wanderley, Dutra, Guilherme Moreira & Wosiacki, Wolmar Benjamin, 2015, The Electric Glass Knifefishes of the Eigenmannia trilineata species-group (Gymnotiformes: Sternopygidae): monophyly and description of seven new species, Zoological Journal of the Linnean Society 175 (2), pp. 384-414 : 392-394

EIGENMANNIA DESANTANAI SP. NOV.

( FIGS 7 , 8 ; TABLE 1)

Diagnosis: Eigenmannia desantanai can be distinguished from other species in the E. trilineata species group by the inferior medial stripe, which is one scale deep (versus two or three scales deep). Eigenmannia desantanai can be further distinguished from the other members of the species group, except for E. waiwai , by the 11 or 12 precaudal vertebrae (versus 13 or 14 in E. antonioi ; 15 in E. guairaca , E. muirapinima , and E. vicentespelaea ; 13 in E. matintapereira ; 14 or 15 in E. microstoma and E. trilineata ; and 13–15 in E. pavulagem ). Eigenmannia desantanai can be differentiated from E. waiwai by the terminal mouth (versus subterminal); the orbital diameter 14.5– 19.6% HL (versus 22.6–28.8%); the length of the anterodorsal process of the maxilla equal to 50% of the width of the posterior nostril (versus 1.5 times the width of the posterior nostril); the depth of the posterodorsal expansion on infraorbitals 1 + 2 approximately equal to the total length of infraorbitals 1 + 2 (versus less than 50% of the length of infraorbitals 1 + 2); and by the dentition pattern of the dentary with 21– 23 teeth distributed in two rows (outermost row with ten to 12 teeth; innermost row with nine to 13 teeth) [versus 37 or 38 teeth distributed in four rows (outermost row with seven teeth; second with 11–15 teeth; third with eight to 15; innermost row with four to eight teeth)].

Description: Morphometric data in Table 1. Body elongate and laterally compressed. Dorsal profile of body slightly convex from rear of head to vertical through middle of anal fin, and then posteroventrally aligned with tip of caudal filament. Ventral profile of body slightly concave from anterior margin of dentary to first anal-fin ray, then posteroventrally aligned with last anal-fin ray. Ventral profile of caudal filament nearly straight. Greatest body depth at vertical through distal margin of pectoral fin.

Head laterally compressed with greatest width at opercular region and greatest depth at posterior margin of supraoccipital. Dorsal profile of head slightly convex from upper lip to vertical through branchial opening. Ventral profile of head slightly concave from anterior margin of lower lip to branchial opening. Snout rounded in profile. Mouth terminal. Upper lip slightly overlapping lower lip. Premaxillary teeth 24(1) or 25(1) distributed in four rows [outermost row with 5(2) teeth; second row with 6(1) or 8(1) teeth; third row with 6(1) or 7(1) teeth; innermost row with 7(1) or 8(1) teeth]. Maxilla with sickle-shaped anterodorsal process equal to 50% width of posterior nostril. Dentary teeth, 21(1) or 23(1) distributed in two rows [outermost row with 10(1) or 12(1) teeth; innermost row with 9(1) or 13(1) teeth]. Dentary teeth all similar in size. Coronomeckelian bone equal to 20% of length of Meckel’s cartilage. Endopterygoid with 14(1) or 15(1) teeth in two series. Mouth rictus at vertical through anterior nostril or in region between nares. Anterior naris tubelike, with posterior margin located at vertical through posterior margin of rictus or in median portion of rictus. Posterior naris elliptical, without tube, located closer to anterior margin of eye than snout tip. Eye approximately circular, covered by skin, laterally located on anterior one-half of head. Antorbital and infraorbitals 1–4 in form of enlarged, partial cylinders with slender osseous arches. Fifth and sixth infraorbitals slender and tubular. Depth of posterodorsal expansion on infraorbitals 1 + 2 equal to total length of infraorbitals 1 + 2. Branchial opening moderately elongate. Branchial membrane joined to isthmus, extending to inferior margin of branchial aperture. Anus and urogenital papilla shifting anteriorly ontogenetically. Anus and urogenital papilla at vertical through posterior margin of orbit in mature specimens.

Cycloid scales present from immediately posterior to head to distal portion of caudal filament. Lateral line complete, with 112(6), 113(1), 118(1), 120(3), 121(1), 125(1), 128*(4), 130(1), or 132(2) perforated scales to vertical through end of anal fin. Longitudinal series of scales above lateral line, 8(7), 9(6), or 10*(7). Scales over anal-fin pterygiophores approximately one-half size of others.

Pectoral-fin rays, ii,12*(18), ii,13(1), or ii,14(1). Distal margin of pectoral fin slightly rounded. Tip of pectoral fin reaching vertical through base of anal-fin rays 16– 20. Anal-fin origin immediately posterior to vertical through pectoral-fin base. Total anal-fin rays, 170– 198 (185*, N = 20; Table 2). Distal margin of anal fin approximately concave. Caudal filament cylindrical, tapering gradually distally, relatively short, and approximately 25% LEA in mature specimens.

Precaudal vertebrae 11(1) or 12(1). Anterior vertebrae 9(2), transitional vertebrae 2(1) or 3(1). Displaced haemal spines 3(2).

Coloration in alcohol: Background colour dark yellow. Dorsal region of head dark brown; gradually becoming lighter ventrally. Lips and suborbital region light brown. Dorsal region of body dark brown, gradually becoming lighter in region overlying anal-fin pterygiophores. Four longitudinal dark stripes along body. Lateral-line stripe thin, one scale deep, extending from first perforated lateral-line scale to distal portion of caudal filament. Superior medial stripe moderately thick, two scales deep, tapering from vertical between base of anal-fin rays 20–28 to posterior onethird of body. Superior medial stripe hardly discernible in specimens over 85.0 mm LEA. Inferior medial stripe thin, one scale deep, extending from vertical through base of anal-fin rays 13–17 to posterior onethird of body. Anal-fin base stripe thick, two scales deep, extending from vertical between base of anal-fin rays 9– 14 to last anal-fin ray. Pectoral and anal fins hyaline, with scattered tiny chromatophores on interradial membranes.

Distribution: Eigenmannia desantanai sp. nov. is known only from Rio Cuiabá, Rio Paraguay basin, Mato Grosso, Brazil ( Fig. 6 ).

Etymology: The epithet ‘ desantanai ’ is in honour of Carlos David de Santana, in recognition of his contributions to our knowledge of the Gymnotiformes .

Material examined

Holotype: Brazil. Mato Grosso: MPEG 31306, 129.2 mm LEA, Rio Cuiabá, Baía de Chacororé, Rio Paraguai basin, Município de Barão de Melgaço , 16°14′58.9″ S, 55°52′44.4″ W, collected by Nupélia’s team, 20 October 2003.

Paratypes: Brazil. Mato Grosso: NUP 12500, 9, 78.3– 106.1 mm LEA, collected with holotype. NUP 3470, 9 + 1CS, 119.8–142.8 mm LEA, Rio Cuiabá, Rio Paraguai basin, Município de Santo Antônio do Leverger , 15°58′26″ S, 55°56′26″ W, collected by Nupélia’s team, 24 October 2002 ; MPEG 31164 , 1 + 1CS, 136.1– 136.8 mm LEA, collected with NUP 3470.

Figures

Figure 6. Map of South America showing the distribution of Eigenmannia antoinoi sp. nov., Eigenmannia desantanai sp. nov., Eigenmannia guairaca sp. nov. sp. nov., Eigenmannia matintapereira sp. nov., Eigenmannia microstoma (1 = type locality), Eigenmannia muirapinima sp. nov., Eigenmannia pavulagem sp. nov. (2 = type locality), Eigenmannia trilineata (3 = type locality), Eigenmannia vicentespelaea, and Eigenmannia waiwai sp. nov. Some symbols represent more than one lot and/or locality.

Figure 7. Lateral view of Eigenmannia desantanai sp. nov., holotype, MPEG 31306, 129.2 mm LEA, Rio Cuiabá, Rio Paraguay basin, Município de Barão de Malgaço, Mato Grosso, Brazil, 16°14′58.9″ S, 55°52′44.4″ W.

Figure 8. Lateral view of head of Eigenmannia desantanai sp. nov., holotype, MPEG 31306, 129.2 mm LEA, Rio Cuiabá, Rio Paraguai basin, Município de Barão de Malgaço, Mato Grosso, Brazil, 16°14′58.9″ S, 55°52′44.4″ W.