Eigenmannia waiwai, 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 : 405-408

EIGENMANNIA TRILINEATA LÓPEZ & CASTELLO, 1966

( FIGS 19 , 20 ; TABLE 4)

Eigenmannia trilineata López & Castello, 1966: 8 (original description; type locality, Nuñez, Río de La Plata, Argentina). Mago-Leccia, 1978: 16 (synonym of E. virescens ). Mago-Leccia, 1994: 20 (catalogue). Braga and Piacentino, 1994: 106 (catalogue). Albert, 2003: 488 (catalogue). López et al., 2003: 65 (in listing of species from Argentina).

Diagnosis: Eigenmannia trilineata can be distinguished from other species in the E. trilineata species group, except E. microstoma , by the suborbital depth 32.5–46.6% 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 trilineata differs from E. microstoma by dentition pattern of the premaxilla with 31–33 teeth distributed in four rows (outermost row with eight or nine teeth; second row with five or six teeth; third row with ten teeth; innermost with seven to nine teeth) [versus 16 teeth distributed in three rows (outermost row with five teeth; middle row with six teeth; innermost row with five teeth)]; the the dentition pattern of the dentary, 23 teeth distributed in two rows (outer row with eight teeth; inner row with 15 teeth) [versus 16 teeth distributed in two rows (outer row with 10 teeth; inner row with six teeth)]; 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).

Description: Morphometric data are presented in Table 4. 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, and 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 overlapping lower lip. Premaxillary teeth, 31(2) or 33(1), distributed in four rows [outermost row with 8(1) or 9(1) teeth; second row with 5(1) or 6(1) teeth; third row with 10(2) teeth; innermost row with 7(1) or 9(1) teeth]. Maxilla with sickle-shaped anterodorsal process equal to width of posterior nostril. Dentary teeth 23(1) distributed in two rows [outer row with 8(1) teeth; inner row with 15(1) teeth]. Dentary teeth similar in size. Coronomeckelian bone equal to 20% of length of Meckel’s cartilage. Endopterygoid with 16(1) or 17(1) teeth in two rows. 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, 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 50% the length of infraorbitals 1 + 2. Branchial opening moderately elongate. Branchial membrane joined to isthmus. Anus and urogenital papilla shifting anteriorly ontogenetically; 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 107(1), 112(2), 114(1), 115(1), 116(3), 117(1), 118(5), 119(2), 121(3), 123(2), 125*(2), 131(2), or 135(1) perforated scales to vertical through end of anal fin. Longitudinal series of scales above lateral line 9*(15), 10(6), 11(3), or 12(2). Scales over anal-fin pterygiophores approximately one-half size of others.

Pectoral-fin rays, ii,14*(20) or ii,15(6). Distal margin of fin approximately straight. 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, 176–217 (195*, N = 26; Table 2). Distal margin of anal fin approximately concave. Caudal filament cylindrical, tapering gradually distally, relatively long, and approximately 50% of LEA in mature specimens.

Precaudal vertebrae 14(3). Anterior vertebrae 11(3); transitional vertebrae 3(3). Displaced haemal spines 3(3).

Coloration in alcohol: Background colour yellowish to dark brown. Head dark dorsally, and gradually becoming lighter ventrally. Lips and suborbital region light yellow. Body dark brown dorsally and gradually becoming lighter to region overlying anal-fin pterygiophores. Four longitudinal dark stripes along body. Lateral line stripe, 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 through base of anal-fin rays 19–35 to posterior one-third of body. Inferior medial stripe moderately thick, two scales deep, extending from vertical through base of anal-fin rays 20–31 to posterior one-third of body. Anal-fin base stripe thick, two scales deep, extending from vertical between base of anal-fin rays 20–35 to last anal-fin ray. Pectoral and anal fins hyaline, with scattered tiny chromatophores on interradial membranes.

Distribution: Eigenmannia trilineata is known from Río de La Plata basin and lower Río Paraná basin, Argentina ( Fig. 6 ).

Remarks: Examination of the type specimens revealed some divergences from data in the original description. The authors gave the number pectoral-fin rays as ‘i,14’ or ‘i,15’ ( López & Castello, 1966: 10; table 1); however, all the types have ii,14 or ii,15 pectoralfin rays. This difference could be a function of the small size of the first unbranched pectoral-fin ray. Furthermore, López & Castello (1966: table 1) cited 193 analfin rays for the holotype; however, we detected 195 anal-fin rays. This difference may also be related to the small size of the first unbranched anal-fin rays.

Additionally, the original description of the colour pattern was described as ‘three conspicuous dark horizontal stripes...’ ( López & Castello, 1966: 11; fig. 1). All types have lost their colour pattern, but specimens recently collected in the type locality (e.g. MACN 7390) have an additional stripe that we refer to in the description as the superior medial stripe.

During an examination of material from the lower Río Paraná and the Río de La Plata, we observed two species of Eigenmannia occurring in these localities: E. trilineata and a species with uniform colour pattern, without longitudinal stripes, designated in this study as E. virescens (see comparative material examined). This proposal is justified by the fact that the original illustration of that species provided by d’Orbigny (in Valenciennes, 1847; plate xiii) indicates that longitudinal dark stripes are absent, and the detailed historical record presented by Papavero (1971) indicates that the localities from which this material originat- ed are the probable type localities. Additionally, other species collected by Alcide d’Orbigny and described by Valenciennes have been shown to have type localities in the Río de la Plata basin, Argentina, as Astyanax orbigyanus (Valenciennes, 1850) , Ancistrus cirrhosus (Valenciennes, 1836) , Cynopotamus argenteus (Valenciennes, 1836) , and Synbranchus pardalis Valenciennes, 1842 (currently S. marmoratus ). Thus, we assign the name E. virescens to the population without dark stripes from the hydrographic system of the lower Río Paraná basin and the Río de La Plata.

Material examined

Type specimens: Argentina. Nuñez : MACN 5470 , holotype , 130.0 mm LEA, Río de La Plata , approximately 34°25′40.27″ S, 58°28′21.2″ W, 24 August 1966. MACN 5471 , 9 paratypes , 79.9–161.3 mm LEA.

Non-type specimens: Argentina: MACN 6003 , 98 + 2 dissected, 89.5–153.6 mm LEA, Río de La Plata , approximately 34°25′57″ S, 58°26′35″ W . MACN 6927 , 60 , 98.5– 155.6 mm LEA, Río Paraná , 31°02′55″ S, 59°47′10″ W . MACN 7023 , 10 , 95.5–143.5 mm LEA, Río San Javier , Río de Paraná basin, 31°29′50″ S, 60°20′32″ W. MACN 7024 , 1, 115.7 mm LEA, Río Paraná basin, 34°31′ S, 59°41′ W . MACN 7390 , 8 , 94.4–118.1 mm LEA, Río de La Plata , 34°25′57″ S, 58°26′35″ W . MACN 7947 , 2 , 119.5 – 145.6 mm LEA, Río Yabebury , Río de Paraná basin, 27°18′11.84″ S, 55°34′11.20″ W . MACN 9306 , 3 , 82.8–87.1 mm LEA, Río Paraná , 27°31′ S, 58°34′ W . MZUSP 111151 , 1 , 95.9 mm LEA, Río de La Plata , 34°25′40.27″ S, 58°28′21.20″ W . MZUSP 22616 , 1 CS, 142.9 mm LEA, Río de La Plata , 34°25′40.27″ S, 58°28′21.20″ W .

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 19. Lateral view of Eigenmannia trilineata, holotype, MACN 5470, 129.9 mm LEA, Río de La Plata, near Nuñes, Río de La Plata basin, Argentina, approximately 34°25′40.27″ S, 58°28′21.2″ W.

Figure 20. Lateral view of head of Eigenmannia trilineata, holotype, MACN 5470, 129.9 mm LEA, Río de La Plata, near Nuñes, Río de La Plata basin, Argentina, approximately 34°25′40.27″ S, 58°28′21.2″ W.