Eigenmannia muirapinima, 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 : 398-401

EIGENMANNIA MICROSTOMA ( REINHARDT, 1852)

( FIGS 13 , 14 ; TABLE 3)

Sternopygus microstomus Reinhardt, 1852: 147 (type locality: Lagoa Santa). Eigenmann & Ward, 1905: 173 (synonym of Eigenmannia virescens ). Eigenmann, 1910: 499 (synonym of E. virescens ). Ellis, 1913: 127 (synonym of E. virescens ). Fowler, 1951: 434 (synonym of E. virescens ). Nielsen, 1974: 48 (in catalogue of type specimens at ZMUC). Mago-Leccia, 1978: 16 (synonym of E. virescens ). Britski, 2001: 19 (types collected by Reinhardt).

Sternopygus virescens, Lütken, 2001: 134 , 161 (description and reference to S. microstomus ).

Eigenmannia microstoma, Mago-Leccia, 1994: 20 (catalogue). Albert, 2003: 488 (catalogue).

Eigenmannia virescens (in part), Alves & Leal 2010: 49 (only specimens from Rio Pandeiros).

Diagnosis: Eigenmannia microstoma can be distinguished from other species in the E. trilineata species group, except E. trilineata , by the suborbital depth 29.9– 40.8% HL (versus 18.4–27.8% in E. antonioi ; 20.8– 28.9% in E. desantanai ; 22.2–27.5% in E. guairaca ; 18.2– 26.1% in E. matintapereira ; 18.7–28.4% in E. muirapinima ; 19.4–27.4% in E. pavulagem ; 21.7– 27.4% in E. vicentespelaea ; and 19.0–28.3% in E. waiwai ). Eigenmannia microstoma differs from E. trilineata by the premaxillary dentition, 16 teeth distributed in three rows (outermost row with five teeth; median row with six; innermost row with five teeth) [versus 31–33 distributed in four rows (outermost row with eight to nine teeth; second row with five to six teeth; third row with ten teeth; innermost with seven to nine teeth)]; by the dentary dentition with 16 teeth distributed in two rows (outermost row with ten teeth; innermost row with six teeth) [versus 23 distributed in two rows (outermost row with eight teeth; innermost row with 15 teeth)]; and 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). Eigenmannia microstoma also differs from other species in the E.trilineata species-group, except E. vicentespelaea , by the length of the coronomeckelian bone, which equals 45% of the length of Meckel’s cartilage (versus 20% of the length of Meckel’s cartilage). Eigenmannia microstoma can be distinguished from E. vicentespelaea by: the terminal mouth (versus subterminal); 11–15 longitudinal series of scales above the lateral line (versus seven or eight); the body depth at the vertical through the tip of longest pectoral-fin ray, 16.9–20.8% LEA (versus 10.5– 14.5%); the body depth at the vertical through the first anal-fin ray, 14.0–18.1% LEA (versus 11.5–13.3%); the head depth at the posterior limit of the supraoccipital bone, 76.1–101.1% HL (versus 68.6–74.7%); the head depth at the orbit, 56.7–78.1% HL (versus 49.3– 55.8%); and the length of anterodorsal process of maxillar, which is equal to the width of the posterior nostril (versus 50% of the width of the posterior nostril).

Description: Morphometric data are presented in Table 3. 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 anal-fin ray. Ventral margin 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. Premaxilla teeth 16(1); distributed in three rows [outermost row with 5(1) teeth; median row with 6(1) teeth; inner row with 5(1) teeth]. Maxilla with sickle-shaped anterodorsal process equal to width of posterior nostril. Dentary teeth 16(1); distributed in two rows [outer row with 10(1) teeth; inner row with 6(1) teeth]. Dentary teeth all similar in size. Coronomeckelian bone equal to 45% length of Meckel’s cartilage. Endopterygoid with 11(1), 13(1), or 16(1) teeth in one or two series. Mouth rictus extending posteriorly to vertical through anterior nostril of, or in region between, naris. Anterior naris tube-like, with posteri- or margin located at vertical through posterior margin of, 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 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 112(2), 117(1), 118(1), 119(2), 120(1), 121(2), 126(1), 128(2), 132(1), 135(1), or 142(1) [syntypes, 121(1), 126(1), 128(1), or 132(1)] perforated scales to vertical through end of anal fin. Longitudinal series of scales above lateral line 11(1), 12(3), 13(6), 14(7), or 15(1) [syntypes, 12(1), 13(3), 14(1), or 15(1)]. Scales over anal-fin pterygiophores approximately one-half the size of others.

Pectoral-fin rays, ii,12(2), ii,13 (6), ii,14(10), or ii,15(5) [syntypes, ii,13(2), ii,14(3), or ii,15(1)]. Distal margin of fin approximately straight. Tip of pectoral fin reaching vertical through base of anal-fin rays 25–27. Analfin origin immediately posterior to vertical through pectoral-fin base. Total anal-fin rays, 173–207 [syntypes, 180–207 total anal-fin rays, N = 15; Table 2). Distal margin of anal fin slightly concave. Caudal filament cylindrical, tapering gradually distally; relatively short and approximately 25% LEA in mature specimens.

Precaudal vertebrae 14(6) or 16(1). Anterior vertebrae 10(6) or 12(1). Transitional vertebrae 3(3) or 4(3). Displaced haemal spines 3(7).

Coloration in alcohol: Background colour pale yellow to dark brown. Head dark brown dorsally and gradually becoming lighter ventrally. Lips and suborbital region yellowish. Body dark brown gradually and 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, two scales deep, tapering from vertical between analfin rays 18–20 and posterior one-third of body. Inferi- or medial stripe moderately thick, two scales deep, extending from vertical between anal-fin rays 15–22 and posterior one-third of body. Anal-fin base stripe thick, two or three scales deep, extending from vertical through base of first to last anal-fin ray. Pectoral and anal fins hyaline, with scattered tiny chromatophores on interradial membranes.

Distribution: Eigenmannia microstoma is known from Rio São Francisco basin, Minas Gerais, Brazil ( Fig. 6 ).

Remarks: Eigenmannia microstoma was considered a junior synonym of E. virescens for years until its revalidation by Mago-Leccia (1994). Mago-Leccia (1994) did not, however, present any basis for recognizing E. microstoma as a valid species, resulting in doubts about the identity of the species. Campos-da-Paz (1997) redescribed E. microstoma and commented that this species has no, or only one or two, body stripes. This information differs from that in the original description ( Reinhardt, 1852), which reports four body stripes in this species. All syntypes have lost their colour pattern, but recently specimens collected from the type locality have been found to bear four stripes on the flanks. We only recognize specimens with four stripes as belonging to E. microstoma . Albert (2001) proposed that E. microstoma could be more closely related to Eigenmannia humboldtii (Steindachner, 1878) and Eigenmannia limbata (Schreiner & Miranda Ribeiro, 1903) than to E. trilineata because of the body depth in mature specimens (more than 11% TL) and total length over 350 mm in sexually mature individuals; however, E. microstoma shares with the other species of the E. trilineata species group the presence of the putative synapomorphy we proposed herein. Therefore, we included E. microstoma as a member of the E. trilineata species group.

Material examined

Syntypes: Brazil. Minas Gerais: all from Município de Lagoa Santa, Rio São Francisco basin. BMNH 1868.7.8.2–3, 2 syntypes, 101.1 – 139.3 mm LEA . ZMUC P2516 (formerly ZMUC 21 ), 1 syntype (only photo and radiograph), 162.8 mm LEA . ZMUC P2517 (formerly ZMUC 23 ), 1 syntype, 153.8 mm LEA . ZMUC P2518 (formerly ZMUC 24 ), 1 syntype, 176.6 mm LEA . ZMUC P2519 (formerly ZMUC 25 ), 1 syntype, 105.1 mm LEA . ZMUC P2520 (formerly ZMUC 26 ), 1 syntype, 101.1 mm LEA .

Non-type specimens: Brazil. Alagoas: MNRJ 24494 , 3 , 130.8 – 178.8 mm LEA, floodplain of Marituba, village of Maribuba do Peixe, Município de Penedo. Minas Gerais : MCNIP 143 , 3 , 99.5 –119.0 mm LEA, Rio Juramento at Juramento Dam . MCP 14109, 1 , 83.6 mm TL (damaged), Rio São Francisco between Município de Três Marias and Pirapora, 18°13′ S, 45°15′ W . MCP 19840, 1, 182.9 mm LEA, same data as MCP 14109 . MCP 45216, 5 + 1CS, 57.7–91.6 mm LEA, Rio Pandeiros, Município de Januária , 15°40′18″ S, 44°38′12″ W . MZUSP 22955 , 2 , 154.6 – 156.6 mm LEA, Rio São Francisco, Município de Três Marias , 18°30′ S, 45°17′ W . MZUSP 24643 , 1 + 1CS, 131.1 mm LEA, Três Marias dam, 18°30′ S, 45°17′ W . USNM 44966, 1, 165.9 mm LEA, Município de Lagoa Santa .

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 13. Lateral view of Eigenmannia microstoma, MCP 19840, 182.9 mm LEA, Brazil, Minas Gerais, Rio São Francisco between Município de Três Marias and Pirapora, Rio São Francisco basin, 18°13′ S, 45°15′ W.

Figure 14. Lateral view of head of Eigenmannia microstoma, MCP 19840, 182.9 mm LEA, Brazil, Minas Gerais, Rio São Francisco between Município de Três Marias and Pirapora, Rio São Francisco basin, 18°13′ S, 45°15′ W.