Moenkhausia lepidura ( Kner, 1858 )

Marinho, Manoela M. F. & Langeani, Francisco, 2016, Reconciling more than 150 years of taxonomic confusion: the true identity of Moenkhausia lepidura, with a key to the species of the M. lepidura group (Characiformes: Characidae), Zootaxa 4107 (3), pp. 338-352 : 340-343

Moenkhausia lepidura ( Kner, 1858)

( Figs. 1–5 , 7 a; Table 1 , 2 )

Tetragonopterus lepidurus Kner, 1858: 80 [rio Guaporé (subsequentely reported by Kner 1959: 177)]; 1859: 176, pl. 8, fig. 20 [detailed description].— Eigenmann & Eigenmann, 1891: 53 [catalog, Amazon from Óbidos to Tabatinga].? Günther, 1864: 328 [literature compilation].

Moenkhausia lepidurus .? Eigenmann, 1910: 438 [in part, only Amazon basin; catalog].

Moenkhausia lepidura lepidura .? Eigenmann, 1917: 68 [key], 98 [in part, only Amazon species with predorsal region with two lateral series of scales anteriory, followed by one medial series; redescription].

Moenkhausia lepidura .? Géry, 1977: 451 [similar to Gymnotichthys hildae ].? Géry 1992: 70, fig. 1 [in part, redescription], 78 [key].? Lima et al., 2003: 148 [in part, only Amazon and Orinoco basins; literature compilation].? Lima et al., 2007: 59 [literature compilation].? Marinho & Langeani, 2010a: 60 [diagnosis of M. mikia ; literature compilation].? Marinho & Langeani, 2010b: 878 [literature compilation; comparative material].? Mirande, 2010: 506 [comments on phylogeny].? Oliveira & Marinho, 2016 [diagnosis of M. abyss ; literature compilation].

Gymnotichthys hildae Fernández-Yépez, 1950: 10 , pl. 2: figs 1 [rio Autana].? Géry, 1977: 438 [key], 451 [similar to Moenkhausia lepidura ]. Géry, 1992: 78 [key].? Lasso, et al., 1997: 41 [type catalog].? Lima et al., 2003: 128 [literature compilation].? Mirande, 2010: 546 [comments on phylogeny].

Diagnosis. Moenkhausia lepidura can be distinguished from all congeners, except M. abyss , M. celibela , M. gracilima , M. hasemani , M. hysterosticta , M. icae , M. inrai , M. lata , M. megalops , M. mikia , and M. loweae , by having a dark blotch on the upper caudal-fin lobe, and lower lobe hyaline (vs. caudal lobes hyaline or with a black blotch on both lobes). Moenkhausia lepidura is distinguished from all the aforementioned species by the arrangement of the predorsal scales, which consists of two median series from the tip of supraocciptal spine followed by one medial series reaching the dorsal-fin origin ( Fig. 5 ) (vs. one median series from the supraocciptal spine to the dorsal-fin origin). The pigmentation of the caudal fin also helps to recognize M. lepidura among the species above, which is black, extending from middle caudal-fin rays to the upper lobe (vs. upper caudal-fin lobe pigmentation not as dark; when black, not located on middle caudal-fin rays).

Description. Morphometrics in Table 1 . Largest specimen examined 84.0 mm SL. Body compressed, greatest body depth slightly ahead of vertical through dorsal-fin origin. Dorsal profile of body convex from upper lip to nares; straight from nares to tip of supraoccipital spine; convex from supraoccipital spine to dorsal-fin origin; straight to slightly convex along dorsal-fin base; straight to slightly convex from posterior terminus of dorsal-fin base to adipose-fin origin; slightly concave along caudal peduncle. Ventral profile of body convex from tip of lower jaw to pelvic-fin origin; straight from pelvic-fin origin to anal-fin origin; straight along anal-fin base and slightly concave along caudal peduncle.

Mouth terminal; upper jaw slightly ahead lower jaw. Premaxillary teeth in two rows, outer with 3 (3), 4* (85) or 5 (10) tricuspid teeth, inner with 5* (97) or 6 (1) tetra- to pentacuspid teeth ( Fig. 4 ). Maxilla extending posteriorly to vertical through anterior margin of eye, with 1 (60) or 2* (38) tricuspid teeth. Dentary with four pentacuspid teeth and a series of 6 – 9 very small conical or tricuspid teeth.

Pectoral-fin rays i* (98), 12 (10), 13* (67), 14 (19), or 15 (2), their tips not reaching pelvic-fin origin. Pelvicfin rays i, 7* (98), their tips reaching or just anterior to anal-fin origin. Anal-fin rays iv (1) or v (6), 20 (13), 21* (29), 22 (42), 23 (11), 24 (1) or 25 (1); last unbranched and first three or four branched anal-fin rays much longer then remaining rays. Four supraneurals, all rod-shaped, with bony lamellae in upper portion. Dorsal-fin rays ii, 9* (98), first unbranched dorsal-fin ray almost half length of second unbranched ray. Dorsal-fin origin slightly posterior to vertical through pelvic-fin origin; base of last dorsal-fin ray anterior to vertical through anal-fin origin. Adipose-fin origin approximately at vertical through base of 16th to 19th branched anal-fin rays. Caudal-fin rays i* (98), 16 (1), 17* (96), or 18 (2), i* (98). Caudal fin forked; lobes of similar size. Dorsal procurrent caudal-fin rays 11 (3) or 12 (4), ventral procurrent caudal-fin rays 9 (3), 10 (2) or 11 (2).

Lateral line completely pored, slightly curved ventrally, with 33 (4), 34 (15), 35* (29), 36 (32), or 37 (5) perforated scales. Scales of anterior portion of predorsal area arranged in pairs, followed by a single median row of scales extending to dorsal-fin origin ( Fig. 5 ). Longitudinal scale rows between dorsal-fin origin and lateral line 5* (95); longitudinal scale rows between lateral line and pelvic-fin origin 3(2) or 4* (60). Single row of 5–9 scales overlying base of anteriormost anal-fin rays. Scale rows around caudal peduncle 14* (90). Small scales along first and second third of upper and lower caudal-fin lobes. Vertebrae 33 (5) or 34 (2). Four branchiostegal rays. Gill rakers on first gill arch 8 (4) or 9 (3) on epibranchial, 1 on intermediate cartilage, 9 (3) or 10(4) on ceratobranchial, none (5) or 1 (2) on intermediate cartilage, and 2 (4) or 3 (3) on hypobranchial. Lateral base of gill rackers expanded, forming a small plate with small denticles extending to the posterior portion of the branchial arch ( Fig. 7 ).

Color in alcohol. Overall coloration yellow to brownish ( Figs. 1 , 2 ). Snout, jaws, and top of head with small dark chromatophores; infraorbitals and opercular areas with larger dark chromatophores. Dorsal portion of body dark. First three dorsal horizontal scale rows on body with slightly reticulated pattern, formed by scales bordered by dark pigment. Humeral spot small, vertically over two scale rows above lateral line, sometimes also over lateral line, and horizontally over second and third lateral-line scales. Dark line at horizontal septum, extending from humeral spot to middle caudal peduncle. Broad longitudinal dark band extending approximately from vertical to dorsal-fin origin to caudal-fin base, sometimes becoming a rounded faint blotch at caudal peduncle. Frequently, superficial pigmentation spread over longitudinal band, more concentrated at vertical through fifth to sixth lateralline scales, gradually becoming fainter towards caudal peduncle, extending vertically over two scale rows. Upper caudal-fin lobe and middle caudal-fin rays with continuous black mark, contrasting with whitish rounded area dorsally on anterior third of caudal-fin lobe; frequently, darker pigmentation limiting whitish area ( Fig. 2 a). Some specimens with caudal-fin black mark restricted to ventral portion of upper lobe and middle rays ( Fig. 2 b). Pectoral, pelvic, dorsal, anal, adipose fin and lower caudal-fin lobe with scattered dark chromatophores.

Color in life. Based on photographs of freshly collected specimens ( Fig. 3 ). Overall coloration silvery. Eye, dorsal and adipose fin orange. Pectoral, pelvic, anal fins, and lower caudal-fin lobe hyaline. Middle caudal-fin rays and distal portion of upper caudal-fin lobe black, proximal portion of upper lobe varying from yellow to red.

Sexual dimorphism. Tiny bony spines distributed on distal portion of first seven pelvic-, and five longest anal-fin rays of mature males.

Distribution. Moenkhausia lepidura is distributed in Amazonas lowlands, including rios Tocantins-Araguaia, Madeira, Negro and lower portions of the Tapajós and Trombetas. It is also distributed in the rio Orinoco basin.

Figures

FIGURE 2. Color variation of Moenkhausia lepidura, all from Brazil: A) MZUSP 18220, 76.9 mm SL, rio Tapajós basin, Pará, B) MZUSP 37458, 66.6 mm SL, rio Guaporé drainage, rio Madeira basin, Mato Grosso, C) MZUSP 112371, 62.4 mm SL, rio Jufari, rio Negro basin, Amazonas, D) MZUSP 6227, 37.8 mm SL, rio Negro basin, Amazonas.

FIGURE 3. Moenkhausia lepidura, color in life. Rio Madeira at Porto Velho, Rondônia, Brazil. Not preserved. Photo by L. Sousa.

FIGURE 4. Upper and lower jaws of Moenkhausia lepidura, MZUSP 37458, 70.0 mm SL, medial view of left side. Scale bar 1 mm.

FIGURE 5. Arrangement of the scales of the predorsal region of Moenkhausia lepidura. MZUSP 76538, 44.4 mm SL.

FIGURE 7. Lateral view of right epibranchial of first branchial arch: A) Moenkhausia lepidura MZUSP 6247, 61.11 mm SL, gill filaments removed, B) M. hasemani MZUSP 91868, 52.0 mm SL. Scale bar 0.2 mm.

FIGURE 1. A) Lectotype of Tetragonopterus lepidurus, NMW 57566, 88.7 mm SL, rio Guaporé, rio Madeira basin, Brazil, B) holotype of Gymnotichthys hildae, MHNL 963, 69.4 mm SL, rio Autana, rio Orinoco basin, Venezuela.

Tables

TABLE 1. Morphometric data of Moenkhausia lepidura. Type specimens not included in the range of non-types. SD for Standard Deviation.

	Moenkhausia lepidura Lectotype	Gymnotichthys hildae Holotype	Non-type specimens n	Mean	SD
Standard length (mm) Percentages of standard length Depth at dorsal-fin origin	88.7 30.0	69.4 23.0	98 48.9–82.8 98 25.9–35.5	64.7 30.9	5.4 2.6
Snout to dorsal-fin origin Dorsal-fin origin to adipose-fin origin Snout to pelvic-fin origin	48.9 35.5 50.0	46.8 - 49.0	98 47.6–56.5 97 35.9–49.8 98 47.5–56.1	49.7 38.5 49.8	1.3 1.5 1.2
Snout to anal-fin origin Pelvic-fin origin to anal-fin origin Dorsal-fin length	70.1 21.2 23.0	66.6 - 24.8	98 65.2–71.5 97 18.1–22.5 98 22.9–30.2	67.8 19.8 26.8	1.2 1.0 1.6
Pectoral-fin length Pelvic-fin length Anal-fin length	18.1 18.0 14.4	19.2 17.1 17.3	98 17.8–23.0 98 15.7–20.8 98 14.3–20.4	20.0 18.2 17.0	1.0 1.1 1.4
Dorsal-fin base length Anal-fin base length Eye to dorsal-fin origin	12.1 23.0 36.4	11.7 23.2 33.7	98 11.4–15.5 98 22.4–26.8 98 33.8–39.5	13.7 24.8 35.9	0.7 1.1 1.3
Pectoral- to dorsal-fin origin Caudal-peduncle length Caudal-peduncle depth	- 10.4 11.7	- 11.7 8.8	97 32.7–41.1 98 10.0–15.5 98 8.9–11.7	36.1 12.0 10.1	1.9 1.0 0.6
Head depth Head length Percentages of head length	25.6 23.2	20.2 25.8	98 22.0–27.0 98 24.1–27.2	24.4 25.5	1.1 0.6
Horizontal eye diameter Snout length Interorbital width	38.1 28.8 39.1	38.0 27.9 34.6	98 37.2–46.2 98 25.2–32.3 98 33.3–40.0	40.9 28.2 36.3	1.6 1.3 1.5
Upper jaw length	41.9	41.9	98 36.4–43.2	39.9	1.4