New Astyanax from the upper rio Tapajós drainage , Central Brazil ( Characiformes : Characidae )

Astyanax utiariti, new species, is described from the upper rio Tapajós drainage, Mato Grosso, Brazil. Astyanax utiariti has a horizontally oval black humeral spot, a lozenge-shaped caudal-peduncle spot, continuing to the tip of the middle caudal-fin rays, and two brown bars in the humeral region that allows its inclusion in the A. bimaculatus species group. It also possesses a black stripe extending along midlateral body. The new species is distinguished from its congeners by a reticulate scale pattern, a black longitudinal stripe, toothless maxilla, larger dentary teeth and teeth of the inner row of the premaxilla with five to seven cusps, body depth 33.3-39.9% of standard length (SL), head length (HL) 23.9-26.4% of SL, caudal-peduncle depth 12.0-13.4% of SL, orbital diameter 28.5-34.3% of HL, interorbital width 32.7-38.4% of HL, 36-38 perforated scales along the lateral line, and 22-26 branched anal-fin rays.


Introduction
The genus Astyanax Baird & Girard is a speciose group of Neotropical characid fishes, comprising almost one hundred described species (Bertaco & Lucena, 2006) and occurring in diverse habitats within freshwater drainages from the southern United States to central Argentina.The nominal species currently assigned to Astyanax probably do not represent a monophyletic entity (Weitzman & Malabarba, 1998), a situation that has long been recognized for the genus (Rosen, 1972).Astyanax was revised by Eigenmann (1921Eigenmann ( , 1927)), whose accounts still constitute the sole all-inclusive review of the genus.The current definition of Astyanax is based on a combination of characters proposed by Eigenmann (1917).
In the last years, Garutti (1995Garutti ( , 1998Garutti ( , 1999Garutti ( , 2003) ) and Garutti & Britski (1997, 2000) revised a group of Astyanax species with a combination of the following characters: a horizontally oval, black humeral spot, a lozenge shaped caudal-peduncle spot, continuing to the tip of the middle caudal rays, and two brown vertical bars in the humeral region.The new species described herein is included in this species group.
The new species is described based on new specimens collected in the upper rio Tapajós drainage during a recent expedition to some of the southern tributaries of the Amazon River in the Central and Western regions of Brazil.

Material and Methods
Counts and measurements follow 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 the lateral line to the scale row nearest to the first pelvic-fin ray.Counts of vertebrae, supraneurals, gill-rakers of the first arch, and procurrent caudal-fin-rays were taken from three cleared and stained (c&s) paratypes prepared according to the method of Taylor & Van Dyke (1985).Values for the holotype are indicated by an asterisk.Statistical tests of differences between the sexes were performed.Tooth counts were taken for all type specimens.Vertebral counts include the four vertebrae of the Weberian apparatus and the terminal half centrum, counted as one vertebra.Lower and upper jaws of one c&s paratype were prepared for scanning electronic microscopy (SEM) analysis.
Measurements were taken point to point with an electronic caliper on the left side of specimens.All measurements other than standard length (SL) are expressed as percents of SL except subunits of the head, which are expressed as percents of head length (HL).

Astyanax utiariti, new species
Figs.  Description.Morphometric data are summarized in Table 1.Body compressed and elongate; greatest body depth usually anterior to dorsal-fin origin.Dorsal head profile from upper lip to vertical through middle orbit convex, and from latter point to supraocciptal tip straight or slightly concave.Profile convex from supraocciptal tip to base of last dorsal-fin ray, and straight towards adipose-fin origin.Ventral head profile convex.Ventral body profile slightly convex to nearly straight from pectoral-fin origin to pelvic-fin origin, and straight to slightly concave towards anal-fin origin.Body profile along anal-fin base slanted posterodorsally.Caudal peduncle elongate, nearly straight to slightly concave along dorsal and ventral margins.Head small.Mouth terminal, lower jaw slightly longer than upper jaw.Maxilla extending posterior to vertical through anterior margin of orbit, slightly curved and aligned at angle of approximately 60 degrees to longitudinal body axis.Anterodorsal border of maxilla concave and posterodorsal border slightly convex.Anteroventral and posteroventral borders convex.
Two tooth rows on premaxilla.Outer row with three or five, tricuspid or pentacuspid teeth, with central cusp longer.Inner row with five teeth, gradually decreasing in size from first to fourth tooth; last tooth smaller, with five to seven cusps, central cusp twice or three times longer and broader than other cusps.Maxilla without teeth.Only three specimens with one conical or tricuspid tooth (n = 107).Three to five anteriormost dentary teeth larger, with five to seven cusps, followed by one or two medium-sized teeth with five cusps, and six teeth with one to three cusps or conical; central cusp in all teeth two to three times longer and broader than other cusps.All cusp tips slightly curved towards inside of mouth (Fig. 2).
Dorsal-fin rays ii,9* (n = 23); first unbranched ray approximately one-half length of second ray.Dorsal-fin origin located posterior to middle of SL and posterior to vertical through pelvic-fin origin.Adipose-fin origin located approximately at vertical through insertion of base of five to seven last anal-fin rays.
Anal-fin rays iii-iv,22-25 (24*, one specimen with 26, mean = 23.6,n = 23).Anal-fin profile smoothly concave in females, nearly straight in males.Anal-fin origin posterior to vertical through base of last dorsal-fin ray in females, and anterior to vertical through base of last dorsal-fin ray in males.Anal-fin rays of males bearing one pair of small, elongate, retrorse bony hooks along posterolateral border of each segment of lepidotrichia, usually along last unbranched ray and eighth branched rays.Hooks usually located along posteriormost branch and distal half to two-thirds length of each ray.
Color in alcohol.Dorsal and dorsolateral portion of head and body dark brown.Dark chromatophores scattered on infraorbitals and opercle.Scales on lateral surface of body bordered with dark brown chromatophores forming reticulate pattern.A black humeral spot horizontally oval, located over second to sixth scales on horizontal row, and extending over two horizontal series of scales above lateral line.Two brown and diffuse vertical bars in humeral region; first located over humeral spot and extending over five or six horizontal series of scales, including lateral line.Second vertical bar, located on first series of scales above lateral line, between seventh to tenth series of scales and extending over two or three horizontal series of scales.A black stripe extending along midlateral body from humeral spot to middle caudal-fin rays, located over second series of scales above lateral line on anterior portion of body, and over lateral line scales on the caudal peduncle.In some specimens, the stripe extends from second vertical bar.Midlateral stripe wide, width becoming gradually narrower forward; maximum width on the caudal peduncle, including the series of lateral line scales and first series above; width of about a scale at the vertical through dorsal-fin tip, and 1/2 of scale near the second vertical bar.Stripe relatively darkest posteriorly and becoming more diffuse anteriorly.All fins with scattered dark chromatophores (Fig. 1).
Sexual dimorphism.Males of A. utiariti are easily recognized by the presence of bony hooks on the anal-and pelvicfin rays (see Description).All males examined possess bony hooks along these fins.Males and females also differ in proportional pectoral-and pelvic-fin lengths (Table 1) and analfin shape, which is concave in females and nearly straight in males.Females also attain larger body sizes than males (69.8-79.3mm SL, mean = 75.1,n = 11 vs 57.8-67.8mm SL, mean = 64.6,n = 12, respectively).Males lack gill gland on first gill arch.
Distribution.Astyanax utiariti is known only from rio Papagaio, a tributary of the upper rio Juruena, upper rio Tapajós drainage, Mato Grosso, Brazil.
Etymology.The name, utiariti, is in reference to the Salto Utiariti, an indigenous word that means in the Pareci nation's language "place of clever people" (utia = clever; halíti = people).Pareci tribe is an indigenous group that lives in the region of the upper rio Tapajós drainage, at type locality.A noun in apposition.

Ecological notes.
At the type-locality the rio Papagaio is large and has several waterfalls, with crystalline water, segments with rapids, a well developed riparian vegetation, and a substrate of stones, rocks, and sand.The specimens of A. utiariti were collected with a seine and gill-nets along the left bank of the river in semilentic stretches.On the right bank of the rio Papagaio is located the "Área Indígena Utiariti," a Brazilian natural reserve.

Discussion
Astyanax utiariti possesses a black, oval humeral spot, that is horizontally elongate, a black, lozenge-shaped caudalpeduncle spot continued into the middle caudal-fin rays, and two brown bars on the humeral region.This new taxon has the basic characters used by Garutti (1995) to diagnose the Astyanax bimaculatus species group, which includes several undescribed and described species of Astyanax from the rio Paraná, rio São Francisco, and rio Amazonas basins.Furthermore, A. utiariti possesses a black stripe extending along midlateral body.
These characteristics allow its inclusion in one of the two putative sub-groups recognized by Garutti (1999) within the bimaculatus species group, the sub-group of species with a black lateral stripe.This sub-group currently includes ten species: A. argyrimarginatus Garutti, A. clavitaeniatus Garutti, A. goyacensis Eigenmann, A. incaicus Tortonese, A. novae Eigenmann, A. rupununi Fowler, A. saltor Travasssos, A. siapae Garutti, A. unitaeniatus Garutti, and A. utiariti.The statement of Garutti (1999) that A. saltor and A. incaicus lack a black lateral stripe by is in error.
Astyanax utiariti differs from A. rupununi by the width of the black lateral stripe (stripe width 1/2 of scale depth vs stripe width 1/5 of scale depth, respectively), larger caudal peduncle depth (12.0-13.4vs 9.1-9.2% of SL), and more cusps on the largest dentary teeth (five to seven cusps vs five cusps).It differs from A. clavitaeniatus, A. incaicus, and A. siapae by the absence of a maxillary tooth (vs one maxillary tooth), black lateral stripe width (stripe width 1/2 of scale depth vs black club-shaped lateral stripe, i.e. larger width on caudal peduncle, strongly narrowed forward, reduced to 1/5 or less of a scale between vertical through dorsal-fin tip and vertical through dorsal-fin origin), shallower body (33.3-39.9vs 37.4-45.5 and 36.6-44.4% of SL).Astyanax utiariti differs from A. clavitaeniatus and A. siapae by a deeper caudal peduncle , respectively.It further differs from A. clavitaeniatus by smaller orbital diameter (28.5-34.3vs 31.9-38.1% of HL), and smaller interorbital width , and from A. siapae by having fewer lateral line scales (36-38 vs 38-45).It differs from A. argyrimarginatus and A. unitaeniatus, by the absence of maxillary teeth (vs one maxillary tooth), and by having fewer lateral line scales (36-38 vs 42-46 and 41-44, respectively).It differs from A. goyacensis by larger orbital diameter   Furthermore, the black lateral stripe width (stripe width 1/ 2 of a scale depth vs stripe width 1/5 of a scale depth) and the chromatophores pattern (reticulate scales vs striped scales) distinguish A. utiariti from the undescribed species of the Astyanax bimaculatus species sub-group with a black lateral stripe from the rio Tapajós drainage, referred by Garutti (1995).
The ichthyofauna of the upper rio Tapajós drainage (above the confluence of rio Teles Pires and rio Juruena) is poorly known.Apart from descriptions of new species, reports on the species composition of that drainage are nonexistent.During the collection expedition to several tributaries of rio Tapajós, rio Madeira, rio Purus and rio Paraguay drainages, A. utiariti was collected only in the rio Papagaio, upper rio Tapajós drainage.Garutti (1995) had also examined many lots of Astyanax from of the rio Branco-Negro, rio Juruá, rio Purus, rio Madeira, rio Tapajós, rio Xingu, and lower rio Amazonas (all tributaries of the Amazonas basin), and from rio Araguaia-Tocantins drainage.Astyanax utiariti was found only in the upper rio Tapajós.Therefore, its geographical distribution is apparentely restricted to this area.