Moenkhausia aurantia, Bertaco, Vinicius A., Jerep, Fernando C. & Carvalho, Fernando R., 2011

Bertaco, Vinicius A., Jerep, Fernando C. & Carvalho, Fernando R., 2011, A new characid fish, Moenkhausia aurantia (Ostariophysi: Characiformes: Characidae), from the upper rio Tocantins basin in Central Brazil, Zootaxa 2934, pp. 29-38 : 30-34

Moenkhausia aurantia , new species

( Figs. 1–3 ; Table 1 )

Holotype. UFRGS 13619, 40.6 mm SL, female, Brazil, Goiás, Nova Roma, córrego Kavanca at fazenda Kavanca, upper rio Tocantins basin, 13º41’34’’S 46º57’45’’W, V. A. Bertaco, F. R. Carvalho & G. L. C. Frainer, 9 Sep 2009.

Paratypes. Brazil: Goiás: Nova Roma, upper rio Tocantins basin: UFRGS 11224, 15 (9), 24.2–37.5 mm SL, UNT 10052, 8 (3), 27.5–36.4 mm SL, stream on GO 112 at locality Lagoa Brava, between Nova Roma and Teresina de Goiás, rio Paranã basin, 13º48’37’’S 46º51’57’’W, V. A. Bertaco, F. R. Carvalho & G. L. C. Frainer, 9 Sep 2009. UFRGS 11251, 23 (7), 5 c&s, 15.6–45.5 mm SL, INPA 34990, 8 (3), 29.2–37.8 mm SL, MCP 45865, 8 (4), 24.3–38.4 mm SL, MZUSP 107827, 8 (3), 27.7–40.0 mm SL, córrego Kavanca at fazenda Kavanca, 13º41’34’’S 46º57’45’’W, V. A. Bertaco, F. R. Carvalho & G. L. C. Frainer, 9 Sep 2009.

Diagnosis. Moenkhausia aurantia can be distinguished from all its congeners by the combination of 3 or 4 scale rows below and 5 or 6 scale rows above the lateral line, 21–25 branched anal-fin rays, 33–35 lateral line scales, 2–4 maxillary teeth, 9–12 dentary teeth, and color pattern composed by hyaline caudal-fin lobes, one diffuse humeral spot, and a one-scale-depth midlateral stripe continuous to the caudal peduncle spot. Among Moenkhausia species, M. aurantia is similar to M. lopesi , from rio Cuiabá basin in the upper rio Paraguay system. It differs from M. lopesi by the lower number of maxillary teeth (2–4 vs. 3–7), total number of dentary teeth (9–12 vs. 14–19), body depth (34.2–40.6 vs. 30.2–34.0% of SL), anal-fin base length (30.8–35.7 vs. 27.4–31.7 % of SL), distal profile of the anal fin (straight to convex vs. deeply concave), and the presence of a faint humeral spot (vs. absent). Furthermore, M. aurantia is distinguished from all congeners in the rio Tocantins-Araguaia basin by the number of lateral line scales (33–35 vs. 27–28 in M. pyrophthalma Costa, 36–37 in M. dasalmas Bertaco, Jerep & Carvalho , 36–38 in M. loweae Géry , and 37–41 in M. pankilopteryx Bertaco & Lucinda ), by the number of branched anal-fin rays (21–25 vs. 17–19 in M. pyrophthalma and M. dasalmas , 26–30 in M. tergimacula Lucena & Lucena ), by the number of humeral spots (1 vs. 2 in M. pankilopteryx and M. dasalmas ), by the absence of a black spot in the upper caudal-fin lobe (vs. present in M. hysterosticta Lucinda, Malabarba & Benine and M. loweae ), and by the absence of a dark spot, saddle-like mark anterior to the dorsal-fin origin (vs. present in M. tergimacula ). See Discussion for detailed comparison with the remaining species of Moenkhausia .

Description. Morphometric data are summarized in Table 1 . Body compressed, moderately short, greatest body depth usually located anterior to dorsal-fin origin. Dorsal profile of head convex from tip of upper jaw to vertical through anterior nostril; slightly straight or convex from that point to tip of supraoccipital spine. Dorsal profile of body slightly convex from posterior tip of supraoccipital spine to base of last dorsal-fin ray, and straight to adipose-fin origin. Ventral profile of body convex from tip of lower jaw to pelvic-fin origin, straight or slightly convex from that point to anal-fin origin, and straight and posterodorsally slanted along anal-fin base. Dorsal and ventral profile of caudal peduncle straight to slightly concave.

The range includes the holotype. SD = Standard deviation.

Mouth terminal, jaw isognathous. Maxilla extending posteroventrally to vertical through anterior half of orbit, aligned approximately at 45 degree angle relative to longitudinal axis of body. Main axis of maxilla straight, with approximately same width along all its length.

Two tooth rows in premaxilla: outer row with three* or four tri- to pentacuspid teeth (mode = 4, n = 30), central cusp longer; inner row with five teeth, gradually decreasing in length from first to fourth, last distinctly smaller, with five cusps; central cusp twice as long and broad as others cusps. Maxilla with two to four teeth (3*, mode = 3, n = 30), three to five cusps, with central cusp slightly longer. Four anteriormost dentary teeth larger, with five cusps, followed by five or eight teeth with one to three cusps. Central cusp in all teeth twice or three times longer and broader than lateral cusps. All cusp tips slightly curved posteriorly towards oral cavity ( Fig. 2 ).

Dorsal-fin rays ii,9* (n = 30); first unbranched ray approximately half-length of second ray. First and second branched rays longest. Dorsal-fin origin posterior to middle of body, at vertical through anterior third of pelvic-fin base. Tip of dorsal fin reaching adipose-fin origin in specimens larger than 35.0 mm SL. Distal margin of dorsal fin nearly straight to somewhat convex. Adipose fin origin at vertical through fourth or fifth last anal-fin rays insertion. Anal-fin rays iv–v,21–25 (iv,24*, mode = iv,23, n = 30). First unbranched ray usually visible only in c&s specimens. Distal profile of anal fin distal profile smoothly concave. Anal fin origin at vertical through base of two or three last dorsal-fin rays. Pectoral-fin rays i,11–12* (mode = 11, n = 30). Tip of pectoral fin surpassing pelvic-fin origin. Pelvic-fin rays i,7* (n = 30). Pelvic-fin origin slightly anterior to vertical through dorsal-fin origin. Tip of pelvic fin reaching and surpassing anal-fin origin. Caudal fin forked, lobes similar in size, 19* principal rays (n = 30). Dorsal and ventral procurrent caudal-fin rays 9–11 and 8–10, respectively (n = 5).

Lateral line complete, with 33–35* perforated scales (34*, mode = 34, n = 30). Scale rows between dorsal-fin origin and lateral line 5 or 6* (mode = 6, n = 30); scale rows between lateral line and pelvic-fin origin 3 or 4* (mode = 4, n = 30). Predorsal scales 10*–12 (mode = 11, n = 30) arranged in regular series. Scale rows around caudal peduncle 14* (mode = 14, n = 30). Axillary scale on pelvic fin origin covering 1 or 2 scales posteriorly. Scale sheath along anal-fin base 8–10* scales (mode = 10, n = 30), in single series, covering base of anteriormost rays. Caudal fin scaled, scales over first third of upper and along half-length of lower caudal-fin lobes; scales gradually decreasing in size posteriorly.

Precaudal vertebrae 15 or 16; caudal vertebrae 17–19; total vertebrae 33 or 34 (n = 5). Supraneurals 4 (n = 5), distal portion widened. Branchiostegal rays 4 (n = 5). First gill arch with six rakers on epibranchial, one between epibranchial and ceratobranchial, eight to nine on ceratobranchial, and two on hypobranchial (n = 5).

Color in alcohol. Overall body color varying from light to pale yellowish. Head dusk to dark brownish dorsally. Region from the second to fifth infraorbital and opercular apparatus silvery. Several small dark melanophores surrounding nares, lips, maxillary, lower jaw and anterior margin of orbit, becoming sparse posteriorly; larger melanophores scattered over surface of infraorbitals 3–6 and opercular series on larger specimens. Overall iris color silvery, darker by presence of black pigment bellow ventral margin of pupil and at dorsal portion of eye. High concentration of melanophores in humeral region, forming inconspicuous vertically elongated humeral spot. Dorsum line darker than body lateral and ventral regions. Dark melanophores scattered over body, except ventral region from lower jaw articulation to urogenital papillae. Dorsal and dorso-lateral scales exhibiting tenuous reticulated pattern due to higher concentration of melanophores at their distal borders. Melanophores distributed along dark longitudinal line, larger than other body melanophores. Subcutaneous longitudinal dark stripe starting thinner at vertical line just anterior to dorsal-fin origin, widening posteriorly up to base of caudal fin, reaching one scale wide. Caudal peduncle with higher concentration of melanophores shaping a caudal black spot continuous to longitudinal line, and extending posteriorly over middle caudal-fin rays. Few melanophores following myoseptum of muscles hypaxialis at lower lateral side of caudal region. Dorsal, pectoral and pelvic fins hyaline with scattered melanophores at interradial membrane and bordering margins of rays. Anal and caudal also hyaline, with scattered melanophores more concentrated at distal margins of those fins ( Fig. 1 ).

Color in life. Overall body and head color pattern silvery to whitish. Melanophore distribution pattern of head, body and fins as described above for alcohol preserved specimens. Body slightly orangish, with higher intensity in ventral regions of head, abdomen, base of anal fin and caudal peduncle. Females with less intense orangish color. Dorsal fin orangish, more intense pigmented at first half length of rays. Distal half of second unbranched and first branched dorsal-fin rays hyaline to whitish. Pectoral fin hyaline. Pelvic fin orangish at its proximal portion. Anal fin orangish, more intense along proximal half of the most anterior anal-fin rays. Distal third of last unbranched and first two branched anal-fin rays hyaline to whitish. Adipose fin orangish, more intense colored at its proximal portion. Caudal fin presenting orange coloration at proximal half of dorsal and ventral lobes rays, middle caudal-fin rays dark by presence of melanophores ( Fig. 3 ).

Sexual dimorphism. Secondary sexual characters were not found on examined specimens. Mature gonads were observed in five dissected and c&s specimens (UFRGS 11251, two males, 35.4 and 36.0 mm SL; three females, 33.2–36.7 mm SL).

Distribution. Moenkhausia aurantia is known from tributaries of the rio Paranã, upper rio Tocantins basin, in the Chapada dos Veadeiros region, Brazilian Cerrado, Goiás, Brazil ( Fig. 4 ).

Etymology. The specific epithet is derived from the Latin aurantium, employed here as an adjective in reference to the distinctive orangish coloration of this species.

Ecological notes. The type locality is around 600 m above sea level. Moenkhausia aurantia inhabits streams, and occurs in semi-lentic and lotic shallow areas (up to 0.8 m deep) with riparian vegetation composed by trees and shrubs ( Fig. 5 ). The streams have transparent water, and bottom with rocks, stones, and sand in some stretches. The new species was syntopically collected with Ancistrus sp., Aspidoras albater , Astyanax sp., A. elachylepis , Characidium sp., Cichlasoma araguaiense , Creagrutus britskii , Eigenmannia sp., Hasemania sp., Harttia sp., Hemiodus cf. ternetzi , Hypostomus sp., Imparfinis sp., Ituglanis sp., Knodus sp., Leporinus sp., Moenkhausia sp., Pimelodella sp., and Steindachnerina amazonica . Stomach contents of five specimens (UFRGS 11251) were mainly composed by Hymenoptera, Hirudinea, filamentous alga and digested vegetal organic matter.

Figures

FIGURE 1. Moenkhausia aurantia, holotype, UFRGS 13619, female, 40.6 mm SL, córrego Kavanca at fazenda Kavanca, upper rio Tocantins basin, Nova Roma, Goiás, Brazil.

FIGURE 2. Image from scanning electron microscope of the upper and lower jaws; left lateral view. Moenkhausia aurantia, paratype, female, UFRGS 11251, 36.7 mm SL. Scale bar = 0.5 mm.

FIGURE 3. Moenkhausia aurantia, paratype, UFRGS 11224, 37.1 mm SL, stream on GO 112 at locality Lagoa Brava, between Nova Roma and Teresina de Goiás, Goiás, Brazil. Just after fixation.

FIGURE 4. Type locality of Moenkhausia aurantia, córrego Kavanca at fazenda Kavanca, upper rio Tocantins basin, Nova Roma, Goiás, Brazil.

FIGURE 5. Geographic known distribution of Moenkhausia aurantia in the upper rio Tocantins basin, Goiás, Brazil. The symbol represents more than one lot and locality.

Tables

TABLE 1. Morphometric data for holotype (H) and 29 paratypes of Moenkhausia aurantia from the upper rio Tocantins basin.

Standard length (mm) Percent of SL Predorsal distance	H 40.6 53.0	Range 30.9–45.5 49.8–54.1	Mean 36.4 52.5	SD – 1.1
Prepelvic distance Prepectoral distance	48.5 28.6	45.6–49.7 26.8–30.8	48.0 28.9	1.1 0.9
Preanal distance Depth at dorsal-fin origin Caudal peduncle depth Caudal peduncle length	62.1 40.6 11.9 11.6	60.9–66.5 34.2–40.6 10.1–12.8 9.4–13.7	63.1 36.7 11.3 11.9	1.3 1.7 0.6 1.1
Anal-fin base Dorsal-fin length	34.9 33.0	30.8–35.7 29.2–36.2	33.2 32.7	1.3 1.6
Pelvic-fin length Pectoral-fin length Head length Percent of HL Snout length Upper jaw length	19.2 23.4 26.9 25.2 51.1	16.6–20.5 20.6–24.9 24.8–27.9 22.7–26.8 47.0–54.7	18.4 23.2 26.8 24.9 50.3	0.8 0.8 0.7 1.0 2.0
Orbital diameter Interorbital width	38.0 31.5	35.0–41.1 30.4–35.0	38.4 32.2	1.5 1.1