Astyanax utiariti, Bertaco & Garutti, 2007

Bertaco, Vinicius A. & Garutti, Valdener, 2007, New Astyanax from the upper rio Tapajós drainage, Central Brazil (Characiformes: Characidae), Neotropical Ichthyology 5 (1), pp. 25-30 : 26-28

Astyanax utiariti , new species

Figs. 1 and 2

Holotype. MCP 40040, 67.8 mm SL, male, rio Papagaio at Pubi beach, tributary of rio Juruena , upper rio Tapajós drainage, Sapezal, Mato Grosso, Brazil, 13º33’35"S 58º24’31"W, 13-14 Jul 2004, ACSI - Brazilian Transcontinental Expedition.

Paratypes. ANSP 185226 , 15 , 57.8 -64.0 mm SL, MCP 40041, 64 (3 c&s), 56.2-79.3 mm SL, MNRJ 29859, 15 , 60.1 -67.0 mm SL, collected with the holotype. MZUSP 5177, 6 , 47.2-66.9 mm SL, rio Papagaio above Salto Utiariti , tributary of rio Juruena, upper rio Tapajós drainage, Mato Grosso, Brazil, approx. 13º02’S 58º16’W, Nov 1966, K. Lenko & P. Pereira .

Non-type material. MCP 40875, 12 , 56.7-76.3 mm SL, collected with the holotype .

Diagnosis. The horizontally elongate oval, black humeral spot, the lozenge shaped caudal-peduncle spot continued into middle caudal-fin rays, and two brown bars in the humeral region, distinguish Astyanax utiariti from most congeners and include it in the A. bimaculatus species group. The new species is distinguished from species of this group by the following combination of characters: a reticulate scale pattern, a black longitudinal stripe, a toothless maxilla, larger dentary teeth, teeth of the inner row of the premaxilla with five to seven cusps, body depth 33.3-39.9% of SL, predorsal distance 51.7-55.5% of SL, caudal peduncle depth 12.0-13.4% of SL, head length 23.9-26.4% 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 (25-29 total).

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 ).

Scales cycloid, moderately large. Lateral line complete. Scales in longitudinal series 36-38 (36*, mean = 37.0, n = 23). Scale rows between dorsal-fin origin and lateral line 6-7 (7*, mean = 7, n = 23); scale rows between lateral line and pelvicfin origin 5-6 (5*, mean = 5, n = 23). Predorsal scales 11-13, arranged in regular series (11*, mean = 11.7, n = 21). Scale rows around caudal peduncle 14-18 (14*, usually 16, mean = 15.7, n = 23). Scale sheath along anal-fin base 9-12 (10*) scales in single series, extending to base of eleventh to thirteenth branched ray.

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.

Pectoral-fin rays i,11-14 (11*, mean = 11.6, n = 23). Pectoral-fin tip reaching or surpassing pelvic-fin origin in males but not in females. Pelvic-fin rays i,7* (three specimens with i,6,i; n = 23). Pelvic-fin origin located anterior to vertical through dorsal-fin origin. Caudal-fin forked, with 19 principal rays. Dorsal procurrent rays 12 (n = 3). Ventral procurrent rays 10- 11 (n = 3).

Precaudal vertebrae 17; caudal vertebrae 17-18; total vertebrae 34-35. Supraneurals 5. Gill-rakers on dorsal limb of outer gill arch 7-8, and on ventral limb 12 (n = 3).

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- 79.3 mm SL, mean = 75.1, n = 11 vs 57.8-67.8 mm 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.

Figures

Fig. 1. Astyanax utiariti, MCP 40040, holotype, male, 67.8 mm SL; rio Papagaio, tributary of rio Juruena, upper rio Tapajós drainage, Sapezal, Mato Grosso, Brazil.

Fig. 2. Astyanax utiariti, MCP 40041, paratype, male, 64.5 mm SL, c&s specimen. Scanning electron microscopy of left side upper and lower jaws.