Eigenmannia guairaca, 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 : 394-396

EIGENMANNIA GUAIRACA SP. NOV.

( FIGS 9 , 10 ; TABLE 1)

Diagnosis: Eigenmannia guairaca can be distinguished from other species in the E. trilineata species group, except E. desantanai , E. microstoma , and E. muirapinima , by the ii,11–12 pectoral-fin rays (versus ii, 13–14 in E. antonioi and E. pavulagem ; ii, 16– 17 in E. matintapereira ; ii, 14–15 in E. trilineata ; ii, 15– 17 in E. vicentespelaea ; and ii, 13–15 in E. waiwai ). Eigenmannia guairaca differs from E. desantanai , E. microstoma , and E. muirapinima by the number of total anal-fin rays, 151–170 (versus 170–198 in E. desantanai and E. muirapinima ; and 173–207 in E. microstoma ). Eigenmannia guairaca can be further distinguished from E. desantanai and E. muirapinima by the five or six endopterygoid teeth (versus 14–15 in E. desantanai and eight or nine in E. muirapinima ). Eigenmannia guairaca differs from E. desantanai by the dentition pattern of the premaxilla with nine or ten teeth distributed in two rows (outermost row with four teeth; innermost row with five or six teeth) [versus 21–23 teeth distributed in two rows (outermost row with ten to 12 teeth; innermost row with nine to 13 teeth)]. Eigenmannia guairaca can be further distinguished from E. microstoma by the suborbital depth, 22.2–27.5% HL (versus 29.9–40.8%); the length of anterodorsal process of the maxilla equal to 50% of the width of posterior nostril (versus equal to the width of the posterior nostril); and the length of the coronomeckelian bone equal to 20% of the length of Meckel’s cartilage (versus 45% of the length of Meckel’s cartilage). Eigenmannia guairaca can be further distinguished from all species in the E. trilineata species group, except E. microstoma and E. pavulagem , by 15 precaudal vertebrae (versus 13 or 14 in E. antonioi , E. muirapinima and E. vicentespelaea ; 11 or 12 in E. desantanai ; 13 in E. matintapereira and E. trilineata ; and 12 or 13 in E. waiwai ).

Description: Morphometric data in Table 1. Body elongate and laterally compressed. Dorsal profile of body nearly straight from rear of head to posterior onethird of anal fin, and then posteroventrally aligned with distal portion of caudal filament. Ventral profile of body posteroventrally aligned from anterior margin of dentary to first anal-fin ray, and then posterodorsally aligned with last anal-fin ray. Ventral profile of caudal filament 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 overlap- ping lower lip. Premaxillary teeth, 9(1) or 10(1); distributed in two rows [outermost row with 4(2) teeth; innermost row with 5(1) or 6(1) teeth]. Maxilla with sickle-shaped anterodorsal process equal to 50% of width of posterior nostril. Dentary teeth 17(1) or 19(1) distributed in two rows [outermost row with 10(1) or 11(1) teeth; innermost row with 7(1) or 8(1) teeth]. Dentary teeth all similar in size. Coronomeckelian bone equal to 20% length of Meckel’s cartilage. Endopterygoid with 5(1) or 6(1) teeth in single row. Mouth rictus at vertical through anterior nostril or in region between nares. Anterior naris tube-like, with posterior margin located at vertical through posteri- or margin 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 anteri- or 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 equals total length of infraorbitals 1 + 2. Branchial opening moderately elongate. Branchial membrane joined to isthmus. 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 113(1), 119(1), 120(1), 122(2), 124(2), 132*(1), or 143(3) perforated scales to vertical through end of anal fin. Longitudinal series of scales above lateral line, 9*(5), 10(5), or 11(1). Scales over anal-fin pterygiophores approximately one-half the size of others.

Pectoral-fin rays, ii,11(3) or ii,12*(8). Distal margin of pectoral fin slightly rounded. Tip of pectoral fin reaching vertical through base of anal-fin rays 16–20. Analfin origin immediately posterior to vertical through pectoral-fin base. Total anal-fin rays 151–170 (155*, N = 11; Table 2). Distal margin of anal fin slightly convex. Caudal filament cylindrical, tapering gradually distally; relatively short and approximately 25% LEA in sexually mature specimens.

Precaudal vertebrae 15(2). Anterior vertebrae 13(2). Transitional vertebrae 2(2). Displaced haemal spines 3(1) or 4(1).

Coloration in alcohol: Background colour pale brown. Dorsal region of head dark brown; gradually becoming lighter ventrally. Lips and suborbital region yellowish. Dorsal region of body brown; gradually becoming lighter to 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 thick, three scales deep, taper- ing from vertical between base of anal-fin rays 20–30 to posterior one-third of body. Inferior medial stripe moderately thick, two scales deep, extending from vertical between base of anal-fin rays 12–23 to posterior one-third of body. Anal-fin base stripe thick, two scales deep, extending from vertical between base of analfin rays 1–16 to last anal-fin ray. Pectoral and anal fins hyaline, with scattered tiny chromatophores on interradial membranes.

Distribution: Eigenmannia guairaca sp. nov. is known only from Riacho Água do Ó, a tributary of the Rio Paranapanema, upper Rio Paraná basin, Paraná, Brazil ( Fig. 6 ).

Etymology: The epithet ‘ guairaca ’ is a reference to the legendary Guairacá, a brave Indian chief who was protector of the lands and the Guarani people. A noun in apposition.

Material examined

Holotype: Brazil. Paraná: MPEG 31307, 133.3 mm LEA, Riacho Água do Ó, tributary of Rio Paranapanema, upper Rio Paraná basin, Município de Santa Fé , 23°01′08″ S, 51°51′37.8″ W, collected by C. Pavanelli and others, 16 December 2008.

Paratypes: Brazil. Paraná: NUP 6467, 8 + 1CS, 81.4– 135.8 mm LEA; MPEG 31165 , 1 + 1CS (damaged), 115.7 mm LEA, collected with holotype .

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 9. Lateral view of Eigenmannia guairaca sp. nov., holotype, MPEG 31307, 133.3 mm LEA, Riacho Água do Ó, upper Rio Paraná basin, Município de Santa Fé, Paraná, Brazil, 23°01′08″ S, 51°51′ 37.8″ W.

Figure 10. Lateral view of head of Eigenmannia guairaca sp. nov., holotype, MPEG 31307, 133.3 mm LEA, Riacho Água do Ó, upper Rio Paraná basin, Município de Santa Fé, Paraná, Brazil, 23°01′08″ S, 51°51′ 37.8″ W.