Eigenmannia antonioi, 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 : 387-392

EIGENMANNIA ANTONIOI SP. NOV.

( FIGS 1B , 2 , 3 , 4B , 5B; TABLE 1)

Eigenmannia trilineata, Montag et al., 2008: 20 (in listing of species from Floresta Nacional de Caxiuanã, Brazil).

Diagnosis: Eigenmannia antonioi can be distinguished from other species in the E. trilineata species

388 L. A. W. PEIXOTO ET AL.

group, except E. microstoma and E. trilineata , by the mouth width 20.0–25.1% HL (versus 13.1–18.4% in E. desantanai ; 12.9–17.5% in E. guairaca ; 12.6– 16.1% in E. matintapereira ; 13.2–18.1% in E. muirapinima ; 10.8–19.0 in E. pavulagem ; 9.5– 17.2% in E. vicentespelaea ; and 9.5–14.6% in E. waiwai ). Eigenmannia antonioi differs from E. microstoma and E. trilineata by the suborbital depth 18.4–27.8% HL (versus 29.9–40.8% and 32.5–46.6%, respectively); by the dentition pattern of the premaxilla with eight to 12 teeth distributed in two rows (outermost row with three to six teeth; innermost row with four to six teeth) [versus 16 teeth distributed in three rows (outermost row with five teeth; median row with six; innermost with five teeth) in E. microstoma ; and the 31–33 teeth distributed in four rows (outermost row with eight or nine teeth; second row with five or six; third row with ten; innermost with seven or nine teeth) in E. trilineata ] and by the length of anterodorsal process of maxillary corresponding to 50% of the width of the posteri- or nostril ( Fig. 4 ; versus equal to the width of the posterior nostril in E. trilineata and E. microstoma ). Eigenmannia antonioi can be further distinguished from E. microstoma by the length of the coronomeckelian bone 20% of the length of Meckel’s cartilage ( Fig. 5 ; versus 45% of the length of Meckel’s cartilage in E. microstoma ). Additionally, E. antonioi can be distinguished from E. trilineata by the depth of the posterodorsal expansion on infraorbitals 1 + 2, which approximately equals the total length of infraorbitals 1 + 2 ( Fig. 1 ; versus less than 50% of the length of infraorbitals 1 + 2 in E. trilineata ), and by eight or nine endopterygoid teeth (versus 17 in E. trilineata ).

Description: Morphometric data in Table 1. Body elongate and laterally compressed. Dorsal profile of body nearly straight from rear of head to vertical through middle of anal fin, and then posteroventrally aligned with distal portion of caudal filament. Ventral profile of body slightly concave along anterior half of abdominal cavity, then posterodorsally aligned with last analfin ray. Ventral profile of caudal filament straight. Greatest body depth at vertical through distal margin pectoral fin.

Head laterally compressed, with greatest width at opercular region and greatest depth at posterior margin of supraoccipital. Dorsal profile of head 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 8(1), 9(2), or 12(1); distributed in two rows [outermost row with 3(1), 4(1), 5(1), or 6(1) teeth; innermost row with 4(2) or 6(2) teeth]. Maxilla with sickle-shaped anterodorsal process equal to 50% of width of posterior nostril. Dentary teeth 8(1), 11(1), 14(1), or 15(1), distributed in one or two rows [outermost row with 6(2), 7(1), or 8(1) teeth; innermost row with 5(2) or 7(1) teeth]. Dentary teeth increasing abruptly in size from the fourth or fifth teeth of outermost row towards rictus. Coronomeckelian bone equal to 20% length of Meckel’s cartilage. Endopterygoid with 8(3) or 9(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 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 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 approximately 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), 115(1), 120(2), 121(1), 122(2), 123(3), 124(4), 126(2), 127(3), 128(4), 130(2), 131(1), or 132*(3) perforated scales to vertical through end of anal fin. Longitudinal series of scales above lateral line, 8(18), 9*(8), or 10(3). Scales over anal-fin pterygiophores approximately one-half size of others.

Pectoral-fin rays ii,13*(13) or ii,14(16). Distal margin of pectoral fin slightly rounded. Tip of pectoral fin reaching vertical through anal-fin rays 16–19. Anal-fin origin immediately posterior to vertical through pectoral-fin base. Total anal-fin rays, 166–207 (190*, N = 29; Table 2). Distal margin of anal fin slightly convex. Caudal filament cylindrical, tapering gradually distally, relatively short and approximately 30% of LEA in mature specimens.

Precaudal vertebrae, 13(1) or 14(3). Anterior vertebrae, 11(3) or 12(1), transitional vertebrae, 2(2) or 3(2). Displaced haemal spines, 3(4).

Coloration in alcohol: Background colour brown. 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 thick, three scales deep, tapering from vertical between base of anal-fin rays 21–33 to posterior one-third of body. Inferior medial stripe moderately thick, two scales deep, extending from vertical between base of anal-fin rays 15–31 to posterior one-third of body. Anal-fin base stripe thick, two or three scales deep, extending from vertical between base of ninth and 20th anal-fin ray to last anal-fin ray. Pectoral and anal fins hyaline, with scattered tiny chromatophores on interradial membranes.

Distribution: Eigenmannia antonioi sp. nov. is known only from Rio Anapu at Floresta Nacional de Caxiuanã, a tributary of the lower portion of Rio Amazonas, state of Pará, Brazil ( Fig. 6 ).

Etymology: The epithet antonioi is in memory to Antônio da Silva Wanderley, grandfather of the first author.

Material examined

Holotype: Brazil. Pará: MPEG 10181, 152.2 mm LEA, Rio Anapu at Floresta Nacional de Caxiuanã, Município de Portel , Rio Amazonas basin, 02°05′0.7″S, 51°29′43.8″W, collected by L. Montag, 25 March 2004.

Paratypes: Brazil. Pará: all from Rio Anapu at Floresta Nacional de Caxiuanã, Município de Portel , Rio Amazonas basin. MPEG 9940 , 1 , 66.4 mm LEA, collected by L. Montag, 10 November 2004. MPEG 10156 , 1 , 97.4 mm LEA, collected by L. Montag, 10 November 2004. MPEG 10167 , 4 , 79.5–112.3 mm LEA, collected by L. Montag, 25 March 2004. MPEG 10182 , 6 + 1CS, 77.0– 118.3 mm LEA, collected by L. Montag, 24 November 2003. MPEG 10186 , 5 , 71.7 – 109.0 mm LEA, 2°05′0.7″ S, 51°29′43.8″ W, collected by L. Montag, 24 November 2003. MPEG 29486 , 2 , 81.2–84.6 mm LEA, collected with holotype. MZUSP 116795 , 2 + 2CS, 107.5– 121.6 mm LEA; INPA 46983 , 2 , 80.7–88.3 mm LEA; MCP 48613, 2 , 88.6 –91.0 mm LEA, collected with MPEG 10182 .

Non-type specimens: Brazil. Pará: all from Rio Anapu at Floresta Nacional de Caxiuanã, Município de Portel, Rio Amazonas basin. MPEG 29487, 11, 63.6–79.3 mm LEA. MPEG 29488, 6, 37.1–74.8 mm LEA. MPEG 10170,

1, 78.7 mm TL (damaged). MPEG 10177, 3 + 1CS, 41.3–75.7 mm LEA. MPEG 11508, 1, 16.1 mm TL (damaged).

Figures

Figure 1. Scanning electron micrographs (SEMs) of infraorbitals 1 + 2, lateral view, anterior to left: A, Eigenmannia antonioi sp. nov. (MPEG 10182, 88.7 mm LEA); B, Eigenmannia matintapereira sp. nov. (MZUSP 109618, 118.3 mm LEA). Arrow indicates the posterodorsal expansion. Abbreviations: DPE, depth of the posterodorsal expansion; LIB, length of the infraorbital bones 1 + 2. Scale bar: 1 mm.

Figure 2. Lateral view of Eigenmannia antonioi sp. nov., holotype, MPEG 10181, 153.2 mm LEA, Rio Anapu at Floresta Nacional de Caxiuanã, Município de Portel, Rio Amazonas basin, state of Pará, Brazil, 2°05′0.7″ S, 51°29′43.8″ W.

Figure 3. Lateral view of head of Eigenmannia antonioi sp. nov., holotype, MPEG 10181, 153.2 mm LEA, Rio Anapu at Floresta Nacional de Caxiuanã, Município de Portel, Rio Amazonas basin, Pará, Brazil, 2°05′0.7″ S, 51°29′43.8″ W.

Figure 4. Schematic illustration of lateral view of maxilla: A, Eigenmannia matintapereira sp. nov. (MZUSP 109618, 118.3 mm LEA); B, Eigenmannia antonioi sp. nov. (MPEG 10182, 88.7 mm LEA). Cartilage represented by grey. Arrow indicates anterodorsal process. Scale bar: 1 mm.

Figure 5. Medial view of dentary: A, Eigenmannia vicentespelaea (MZUSP 83461, 152.1 mm LEA); B, Eigenmannia antonioi sp. nov. (MPEG 10182, 88.7 mm LEA), showing differents lengths of coronomeckelian bone, equal to 45% the length of Meckel’s cartilage in E. vicentespelaea and to 20% the length of Meckel’s cartilage in E. antonioi sp. nov. Abbreviations: ang-art, anguloarticular; mc, Meckel’s cartilage; cb, coronomeckelian bone; d, dentary; r, retroarticular. Cartilage represented by grey. Scale bars: 2 mm.

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.