New species of Moenkhausia Eigenmann ( Ostariophysi : Characidae ) from the upper rio Tocantins basin in Central Brazil

Moenkhausia dasalmas is described from the upper rio Tocantins basin, in the Chapada dos Veadeiros region, Goiás State, Central Brazil. The new species differs from all congeners by the presence of iii,9 rays in the dorsal fin. It can also be distinguished from its congeners by the presence of two humeral spots (first one vertically elongate and second one faint), by the number of branched anal-fin rays (17-19), lateral line scales (36-37), maxillary teeth (4-5), and a vertical dark spot in the caudal peduncle end.


Introduction
The genus Moenkhausia Eigenmann is a speciose group of characid fishes comprising 71 valid species widespreadly distributed in the Neotropical Cis-Andean river basins, except for those in Patagonia (Lima et al., 2003;Eschmeyer & Fricke, 2010;Marinho, 2010).None of the diagnostic characters presently used to recognize Moenkhausia is unique to the genus, e.g.premaxillary teeth in two rows, five or more teeth on the inner premaxillary row, complete lateral line, and caudal fin scaled, but shared with other incertae sedis Characidae such as Astyanax Baird & Girard, Hemigrammus Gill, and Hyphessobrycon Durbin.Eigenmann (1917) is still the most complete reference to the taxonomy of Moenkhausia, and Géry (1977) made the last survey on the genus presenting a comparative key and brief diagnosis to the species.Those authors recognized species groups based mainly on similarities of body depth, scale counts and color pattern.No hypothesis of intrageneric relationships of Moenkhausia species is available at the moment, and the genus is probably non-monophyletic according to Mirande (2010), whose weighted parsimony phylogenetic analysis of Characidae presented Moenkhausia as a paraphyletic genus with Bario Myers, inside of a new redefined Tetragonopterinae.
The new species was collected in rivers and streams of the upper rio Tocantins basin, in the Chapada dos Veadeiros region, during a recent expedition, and is herein described.

Material and Methods
Counts were taken as described by Fink & Weitzman (1974), with the exception of the number of scale rows below the lateral line, which were counted from the scale row ventral to lateral line to the scale row nearest the first pelvic-fin ray.Counts of vertebrae, supraneurals, gill rakers on the first arch, branchiostegal rays, procurrent caudal-fin rays, and small dentary teeth were taken from cleared and stained (c&s) specimens prepared according to Taylor & van Dyke (1985).The count of unbranched dorsal-fin rays does not include the tiny ray commonly observed only in cleared and stained specimens.Vertebral counts include the four vertebrae of the Weberian apparatus, and the terminal centrum as a single element.Drawings of the upper and lower jaws and the infraorbital series of one c&s specimen were prepared under a stereomicroscope with camera lucida.
Measurements were made with an electronic caliper from the left side of the specimens, and presented as percents of the standard length (SL) or the head length (HL).In the description, the asterisk indicates the value presented by the holotype.In the list of paratypes and material examined, the whole number of specimens in the lot is followed by the number of those counted and measured, and cleared and stained (c&s), in parentheses.
Specimens examined belong to the following institutions: Two tooth rows in the premaxilla: outer row with three* to four tri-to pentacuspid teeth (mode = 3, n = 22), central cusp longer; inner row with five teeth, gradually decreasing in length from first to fourth, last distinctly smaller, with five to seven cusps; central cusp twice as long and broad as others cusps.Maxilla with four to five* teeth (mode = 4, n = 22), three to five cusps, with central cusp slightly longer.Four anteriormost dentary teeth larger, with five or seven cusps, followed by one medium-sized tooth with five cusps, and five or seven teeth with one to three cusps.Central cusp in all teeth two to three times as long and broad as other cusps.All cusp tips slightly curved posteriorly towards inside mouth (Fig. 3).
Dorsal-fin rays iii,9* (n = 22); first unbranched ray approximately one-fifth to one-seventh of second unbranched ray, which is approximately half-length of third unbranched ray.First branched rays longest.Distal margin of dorsal fin nearly straight to somewhat convex.Adipose fin origin approximately at vertical through last anal-fin ray insertion.Anal-fin rays iv-v,17-19 (iv,18*, mode = iv,18, n = 22).First unbranched ray usually apparent only in c&s specimens.Distal profile of anal fin distal profile smoothly concave in the specimens smaller than 34.0 mm SL, and concave in the specimens larger than 34.9 mm SL.Anal fin origin posterior to vertical through base of last dorsal-fin ray.Pectoral-fin rays i,12-13* (mode = 12, n = 22).Pelvic-fin rays i,7* (n = 22).Pelvic-fin origin slightly anterior to vertical through dorsalfin origin.Tip of pelvic fin trespassing genital opening but not reaching anal-fin origin.Caudal fin forked, lobes similar in size, 19* principal rays (n = 22).Dorsal and ventral procurrent caudal-fin rays 12-13 and 11-12, respectively (n = 3).

Color in alcohol.
Overall ground color of body varying from whitish to dark yellowish (Figs. 1 and 5).Dorsal portion of snout, head and body darker than remaining regions.Small melanophores scattered all over head and body, including abdominal region.Larger melanophores scattered over orbital series and opercular apparatus.Scales of longitudinal rows above lateral line series with reticulated color pattern, due to higher concentration of melanophores on their distal margin.Specimens larger than 35.0 mm SL also with a reticulated pattern on most anterior scales of longitudinal rows bellow lateral line series.Two vertically elongate humeral spots, separated by a less pigmented, but not completely pale area.First humeral spot conspicuous, three to four scales wide, narrowing ventrally, and vertically extending over four longitudinal scale rows above lateral line series, and three longitudinal scale rows bellow it.Second humeral spot diffuse, not as dense pigmented as first one, two to three scales wide, fainting posteriorly and ventrally, and extending vertically over four longitudinal scale rows above lateral line series, and at most one longitudinal scale row bellow it.Longitudinal stripe brownish, thinner than scales depth or absent, generally with a denser amount of scattered melanophores along its length.Longitudinal stripe, when present, extending from second humeral spot and contacting caudal peduncle spot on larger specimens, or falling short vertical through adiposefin insertion on smaller.Chevron-shaped striae (chevronshaped bars) posteriorly diverging from longitudinal line, following mioseptum lines, more evident on specimens with longitudinal line not well pigmented (Fig. 5).Caudal peduncle spot faint and vertically expanded, sometimes overlapping base of caudal-fin rays, reaching at most six longitudinal scale lines on larger specimens, but not reaching dorsal and ventral margins of caudal peduncle.All fins hyaline with some melanophores scattered along interradial membranes.Adipose fin hyaline, rarely with dispersed melanophores.were mainly composed by Hymenoptera, Coleoptera (adults) and some fish scales, but autochthonous insects and digested vegetal organic matter (seeds) was also found.

Discussion
The new species, Moenkhausia dasalmas, is herein assigned to Moenkhausia according to the traditional definition of the genus given by Eigenmann (1917Eigenmann ( , 1918) ) and followed by Géry (1977), which is still in use (Bertaco & Lucinda, 2006;Lucinda et al., 2007;Marinho, 2010;Sousa et al., 2010) due to the lack of a cladistic definition of the genus.Among the subdivisions based on body depth and number of scales above and below the lateral line that Géry (1977) assigned to the genus, Moenkhausia dasalmas is included in the M. chrysargyrea species-group, whose species possess seven or more scales above, and five or more scales below the lateral line, and a relatively deeper body.The new species differs from the representatives of that group of species, which includes M. chrysargyrea (Günther), M. comma Subsequently to Géry (1977), three other species of Moenkhausia that could be assigned to the M. chrysargyrea species-group were described: M. margitae Zarske & Géry, from the rio Ucayali drainage in Peru, M. moisae from the rio Maroni and Mana drainages in French Guiana, and M. pankilopteryx from rio Tocantins drainage.Moenkhausia  dasalmas can be distinguished from all these species by the number of branched anal-fin rays (17-19 vs. 25-34).Additionally, it can be distinguished from M. margitae by the shape of the first humeral spot (vertically elongate vs. horizontally elongate); and from M. moisae by number of lateral line scales (36-37 vs. 41-47).
Moenkhausia dasalmas possesses a reticulated color pattern over the body, and a vertically elongate humeral spot.These two characters are color based diagnostic features for the M. oligolepis species complex (Costa, 1994;Lima & Toledo-Piza, 2001;Benine, 2002;Lima et al., 2007;Benine et al., 2009;Sousa et al., 2010) when associated with the presence of a conspicuous and broad caudal peduncle spot preceded by a pale light area (except M. diktyota), and frequently, reddish eyes on live specimens.This group consists of M. oligolepis Günther, M. sanctaefilomenae Steindachner, M. cotinho Eigenmann, M. pyrophthalma Costa, M. diktyota, and M. forestii Benine, Mariguela & Oliveira.Moenkhausia dasalmas does not belong to the M. oligolepis species complex by the absence of a conspicuous and broad caudal peduncle spot and reddish eyes on live specimens, and also differs from the species of this group by the larger number of perforated scales on the lateral line (36-37 vs. at most 34), and longitudinal scale rows above (7-8 vs. at most 6) and bellow (6-7 vs. less than 4) the lateral line.
The dorsal fin in the characid species is commonly constituted by unbranched and branched rays, generally the common condition is two unbranched rays followed by nine branched rays (ii,9), or by eight branched rays (ii,8), as found in the integrants of the "clade A" (sensu Malabarba & Weitzman, 2003).Most characids present two evident anteriormost unbranched rays, but sometimes a tiny and barely developed ray can be present just anterior to these ones, which can be seen externally or under the skin on cleared and stained specimens.Moenkhausia dasalmas however, present one tiny unbranched ray under the skin, followed by three larger posteriorly increasing in length unbranched rays in the dorsal fin.A similar pattern, constituted by the presence of three developed unbranched rays in the dorsal fin, is also found in in Astyanax hermosus Miquelarena,Protogino & López (iii,[8][9][10] Moenkhausia dasalmas inhabits headwater environments and has reduced number of branched anal-fin rays and lower body depth, two of the main characters of the Astyanax scabripinnis species complex (Bertaco & Lucena, 2006).It and pelvic-fin origin 6-7* (mode = 7, n = 22).Predorsal scales 13-14* (mode = 13, n = 16) arranged in regular series.Scale rows around caudal peduncle 16-18* (mode = 16, n = 16).Axillary scale on pelvic fin origin covering 1-2 scales posteriorly.Scale sheath along anal-fin base 7-10 scales (9*, mode = 8, n = 19), in single series, covering base of anteriormost rays.Caudal fin scaled, scales over base of upper and along first third of lower caudal-fin lobes; scales gradually decreasing in size posteriorly.

Moenkhausia dasalmas, new species Figs. 1-5
ANSP, Academy of Natural Sciences, Philadelphia; CAS, California Academy of Sciences, San Francisco; INPA, Instituto Nacional de Pesquisas da Amazônia, Manaus; MCP, Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre; MNRJ, Museu Nacional, Rio de Janeiro; MZUSP, Museu de Zoologia da Universidade de São Paulo, São Paulo; UFRGS, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, and USNM, National Museum of Natural History, Smithsonian Institution, Washington D.C. 41-47 in M. moisae, and 31-35 in the remaining species), and from M. pankilopteryx by the number of maxillary teeth (4-5 vs. 2-3) and the shape of the caudal peduncle spot (vertically elongate vs. horizontally elongate in M. pankilopteryx).Morphometric data 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.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.Maxilla slightly widened anteroposteriorly.

Table 1 .
Morphometric data for holotype and 15 paratypes of Moenkhausia dasalmas from the upper rio Tocantins basin.The range includes the holotype.SD = Standard deviation.
Sexual dimorphism.Secondary sexual characters were not found on examined specimens.Immature gonads were observed in one dissected and c&s specimen (UFRGS 11194, 27.3 mm SL).Distribution.Moenkhausia dasalmas is known from tributaries of the rio das Almas, rio Paranã drainage, upper rio Tocantins basin, in the Chapada dos Veadeiros region, Brazilian Cerrado, Goiás, Brazil.