Astyanax elachylepis, Bertaco & Lucinda, 2005

Bertaco, Vinicius A. & Lucinda, Paulo H. F., 2005, Astyanax elachylepis, a new characid fish from the rio Tocantins drainage, Brazil (Teleostei: Characidae), Neotropical Ichthyology 3 (3), pp. 389-394 : 390-392

Astyanax elachylepis , new species

Figs. 1-3

(1, 91.1 mm SL); UNT 2159 (1, 102.7 mm SL) , sítio Estrela, Silvanópolis , approx. 11º09’S 48º10’W, 11 May 1996, A. L. G. Borges. UNT 2154 (1, 62.4 mm SL) , córrego Taboca , Paranã, approx. 12º29’S 48º13’W, 7 Aug 2000, NEAMB-UFT. UNT 2155 (1, 97.7 mm SL) , rio Maranhão, fazenda Traçadal , Paranã, approx. 12º29’S 48º13’W, 2 Mar 2000, NEAMB-UFT .

Holotype. MCP 37568 (91.7 mm SL, male), ribeirão Arara about 500 m of the mouth of rio Maranhão at Rosariana, Niquelândia, Goiás, Brazil, approx. 14º02’S 48º26’W, 14 Jul 1992, R. E. Reis, E. H. Pereira, J. P. da Silva & L. A. Porto.

Paratypes. Brazil, Goiás: rio Tocantins drainage: MCP 15862 (2, 72.0- 105.6 mm SL) , ribeirão da Lage on road to fazenda Aranha (Codemin), Niquelândia , approx. 14º25’S 48º45’W, 17 Jul 1992, same collectors of the holotype. MCP 15922 (1, 91.1 mm SL) , rio do Peixe, tributary of rio Bagagem, between Niquelândia and Colinas , Niquelândia , approx. 14º27’S 48º14’W, 16 Jul 1992, same collectors of the holotype. MCP 16054 (15, 2 c&s, 44.3-82.1 mm SL) , collected with the holotype. UNT 740 (1, 74.9 mm SL) , rio Maranhão, Niquelândia , approx. 14º40’23"S 48º54’37"W, 13 Aug 1997, D. F. Moraes. MZUSP 40533 (112, 65.8-127.4 mm SL) , ribeirão Macambira, next the bridge on road GO 112, Iaciara , approx. 14º10’S 46º39’W, 14 Sep 1988, J. C. Oliveira & W. J. M. Costa . Pará: MZUSP 30258 (17, 94.6-117.5 mm SL) , rio Itacaiunas, about 10 km E of N-4, Serra dos Carajás at Igarapé , approx. 05º52’S 50º32’W, 13 Oct 1983, M. Goulding. MZUSP 58093 (16, 93.0- 138.3 mm SL) , rio Itacaiunas, Caldeirão, Igarapé do Pojuca , approx. 05º52’S 50º32’W, 15 Oct 1983, M. Goulding . Tocantins: UNT 1891 (10, 47.9-84.0 mm SL) , rio das Pedras, São Salvador , approx. 12º39’S 48º18’W, 5 Aug 2004, NEAMB-UFT. UNT 2033 (36, 13.5-20.4 mm SL) , lagoa da Ponte, near the bridge of the rio Tocantins, Porto Nacional , 10º52’S 48º25’W, 11 Nov 1995, NEAMB-UFT. UNT 2036 (1, 56.4 mm SL) , córrego Sussuarana, Brejinho de Nazaré , approx. 11º01’S 48º34’W, 15 Feb 2002, NEAMB-UFT. UNT 2037 (3, 78.8-96.5 mm SL) , rio Paranã, fazenda Traçadal , Paranã, approx. 12º30’S 48º12’W, 17 Nov 1998, NEAMB-UFT. UNT 2157 (1, 98.6 mm SL) , córrego Albano, near the mouth of rio Paranã, Paranã, approx. 12º34’S 48º06’W, 9 Dec 1998, NEAMB-UFT. UNT 2158 (2, 94.1-114.1 mm SL) , córrego Cipó, Paranã, approx. 12º29’S 48º13’W, 26 Jan 1999, NEAMB-UFT .

Additional material (non types). Brazil, Goiás: UNT 739 (1, 91.4 mm SL), rio das Almas, approx. 14º37’S 49º03’W, 11 Oct 1995. MZUSP 26519 (1, 103.5 mm SL), rio Resende, tributary of rio Vermelho, about 10 km of Buenolândia, approx. 15º49’S 50º19’W, 7-13 Dec 1981. MZUSP 58622 (4, 100.8- 117.5 mm SL), rio Angélica/ Bezerra, Parque Estadual de Terra Ronca, São Domingos, approx. 13º25’S 46º20’W, 11 Sep 1999. Mato Grosso: MZUSP 48278 (6, 73.8-109.8 mm SL), córrego Fundo, tributary of left margin of rio Garças, rio Araguaia drainage, Barra do Garças, approx. 15º53’S 52º47’W, 15 Nov 1993. Pará: MZUSP 58219 (1, 143.8 mm SL), igarapé Salobo, tributary of rio Itacaiunas, Parauapebas, 05º46’50"S 50º32’48"W, Nov 1997. Tocantins: MZUSP 84116 (1, 64.5 mm SL), rio Palma, Conceição do Tocantins, approx. 12º22’S 47º03’W, 1 Aug 2002. UNT 445 (1, 106.8 mm SL), rio Palmeiras drainage, tributary of the rio Palmas, rio Paranã drainage, approx. 12º10’S 46º50’W, 28 Oct 2002. UNT 1761 (1, 67.1 mm SL), córrego Albano, near the mouth of rio Paranã, Paranã, approx. 12º34’S 48º06’W, 4 Aug 2004, NEAMB-UFT. UNT 1804 (1, 59.5 mm SL), rio das Lages, Paranã, approx. 12º35’S 48º02’W, 3 Aug 2004, NEAMB- UFT. UNT 1869 (1, 81.7 mm SL), córrego Calango, São Salvador, approx. 12º44’S 48º20’W, 4 Aug 2004, NEAMB-UFT. UNT 2153 Diagnosis. Astyanax elachylepis is distinguished from its congeners, except A. anterior Eigenmann, 1908 , A. bourgeti Eigenmann, 1908 , A. erythropterus (Holmberg, 1891) , A. festae (Boulenger, 1898) , A. integer Myers, 1930 , A. microlepis Eigenmann, 1913 , A. pellegrini Eigenmann, 1907 , and A. symmetricus Eigenmann, 1908 , by the higher number of lateral-line scales (48-53 vs 30-45, respectively). Astyanax elachylepis differs from the species listed above, except A. microlepis and A. anterior by a lower number of anal-fin rays (ii-iv, 22-27 vs 28-45). Astyanax elachylepis differs from A. microlepis by the number of branched anal-fin rays (22-27 vs 19-22), and by the presence of a large black caudal peduncle spot (vs absence of the caudal peduncle spot, or when present, smaller and approximately lozenge-shaped). Astyanax elachylepis differs from A. anterior by the presence of one or two vertically-elongated humeral spots (vs one ovate or horizontally elongated humeral spot). Furthermore, A. elachylepis differs from Astyanax species with high lateral line counts (the eight aforementioned species) by the presence of small bony hooks in dorsal-, anal-, pelvic-, and pectoral- fin rays of males vs absence of bony hooks in dorsal- and pectoral- fin rays.

Description. Morphometric data summarized in Table 1. Body compressed and elongate; greatest body depth usually anterior to dorsal-fin origin. Dorsal head profile straight or slightly concave. Profile convex from supraocciptal tip to base of last dorsal-fin ray, and straight towards adipose-fin origin. Ventral profile of head 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 posterodorsally slanted. Caudal peduncle elongate, nearly straight to slightly concave along dorsal and ventral margins.

Snout rounded from margin of upper lip to vertical through anterior nostrils. Head small. Mouth terminal. Maxilla extending posteriorly to under center of orbit, and slightly curved aligned at angle of approximately 45 degrees to longitudinal body axis. Anterodorsal border of maxilla concave and posterodorsal border slightly convex. Anteroventral and posteroventral borders convex. Maxilla slightly widened posteriorly.

Two tooth rows on premaxilla. Outer row with three or four, tricuspid or pentacuspid teeth with central cusp longer. Inner row with five teeth, gradually decreasing in length from first to third teeth; last two smaller, with five to seven cusps, with central cusp twice or three times longer and broader than other cusps. Maxilla with one or two (usually one), tricuspid or pentacuspid teeth, with central cusp longer. Three or four anteriormost dentary teeth larger, with seven cusps, followed by one or two teeth of medium sized 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. 3).

Dorsal-fin rays ii, 9 (n = 66); 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. Dorsal-fin rays of males bearing one or two pairs of small retrorse bony hooks along posteroventral border of each lepidotrichia segment, usually between first and eighth branched rays, and located along posteriormost branch and on distal third length of each ray. Adipose-fin located approximately at vertical through insertion of base of 21 st -22 nd anal-fin rays.

Anal-fin rays ii-iv, 23-25 (rarely 22 or 26-27, mean = 24.2, n = 66). First unbranched ray visible only in c&s specimens. Anal-fin profile smoothly concave in females, and nearly straight in males. Anal-fin origin posterior to vertical through base of last dorsal-fin ray. 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 20 th branched rays; hooks more numerous along second through seventh branched rays. Hooks usually located along posteriormost branch and distal half to two-thirds length of each ray.

Pectoral-fin rays i, 11-15 (mean = 12.5, n = 66). Pectoral-fin tip not reaching pelvic-fin origin in males and females. Pectoral-fin rays of males similar to those present on dorsal-fin rays. Pelvic-fin rays i, 7 (n = 66). Pelvic-fin origin located anterior to vertical through dorsal-fin origin. Pelvic fin of males usually bearing one retrorse bony hook per lepidotrichia along ventromedial border of second to fourth branched rays. Hooks usually located along posteriormost branch and distal half to two-thirds length of each ray. Caudal-fin forked, with 19 principal rays. Dorsal procurrent rays 11-13 (n = 2). Ventral procurrent rays 10-11 (n = 2).

Scales cycloid, moderately large. Lateral line complete. Scales in longitudinal series 48-52 (rarely 53, mean = 49.9, n = 65). Scale rows between dorsal-fin origin and lateral line 8-10 (mean = 9, n = 66); scale rows between lateral line and pelvicfin origin 6-8 (usually 7, mean = 7.1, n = 66). Predorsal scales 12-15, arranged in regular series (mean = 13.5). Scales rows around caudal peduncle 18-20 (mean = 19.5). Scale sheath along anal-fin base 12-22 scales in single series, extending to base of fifteenth to twenty-second branched ray.

Precaudal vertebrae 16-17; caudal vertebrae 19; total vertebrae 35-36. Supraneurals 5. Gill-rakers 7-8/10-11 (n = 2).

Color in alcohol. Dorsal and dorsolateral portion of head and body dark brown. Scales on lateral and ventral surface of body weakly pigmented. Two humeral spots; first black and narrow, large and vertically elongate, located over second to fourth lateral line scales and extending over five or six horizontal series of scales, including lateral line. Second humeral spot, dark and very diffuse, 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. Second humeral spot not visible in some specimens. Midlateral body with silvery stripe extending from humeral spot to caudal-peduncle. Large, horizontally elongate, black spot on caudal peduncle forming lozenge or square spot, and extending over middle caudal-fin rays. Remaining fins lacking distinctive patches of pigmentation ( Fig. 2). Some specimens examined just some months after fixation in formalin (UNT 1891), yet presented dorsal, pelvic, anal and caudal fins red-orange pigmented.

Sexual dimorphism. Males of A. elachylepis are easily recognized by the presence of bony hooks on the dorsal-, anal-, pectoral-, and pelvic-fin rays (see Description). All males examined possess bony hooks along these fins (76.5-115.0 mm SL). Males and females also slightly differ concerning pectoral and pelvic-fin lengths ( Table 1) and anal-fin shape, which is concave in females and nearly straight in males.

Distribution. Astyanax elachylepis is known from rio Tocantins drainage, Brazil ( Fig. 1).

Etymology. The name elachylepis is from Greek, elachis, small, short, little, plus lepís, meaning scales, alluding to the small size of scales. A noun in aposition.