Hyphessobrycon ataktos, Marinho & Dagosta & Birindelli, 2014

Marinho, Manoela M. F., Dagosta, Fernando C. P. & Birindelli, José L. O., 2014, Hemigrammus ataktos: a new species from the rio Tocantins basin, central Brazil (Characiformes: Characidae), Neotropical Ichthyology 12 (2), pp. 257-264 : 258-261

Hyphessobrycon ataktos , new species Figs. 1-2

Moenkhausia sp. Menezes, Oyakawa & Birindelli, 2013: 31, fig. 15 [same picture as Fig. 1a ].

Holotype. MZUSP 113725 , 37.7 mm SL, Brazil, Tocantins State, Natividade, córrego Cocal on road TO-280, rio Manoel Alves drainage, rio Tocantins basin, 11°42’50.2”S 47°35’40.2”W, 2 Dec 2012, J. Birindelli, F. Dagosta, M. Loeb & C. Santos.

Paratypes. All from Brazil, Tocantins State, rio Tocantins basin . DZSJRP 18431 , 5 , 26.2-29.5 mm SL ; INPA 39537 , 5 , 25.3-28.3 mm SL ; MCP 47869, 5 , 23.3-33.1 mm SL ; MZUEL 7019 , 5 , 23.6- 28.5 mm SL ; MZUSP 47846 , 331 , 9.1-36.8 mm SL, 11 c&s, 20.3- 32.6 mm SL, Natividade, Ribeirão da Sede, tributary of ribeirão Formiguinha at Fazenda São Judas , approximately 30 km north of Natividade , approximately 11º31’00”S 47º52’00”W, 2-9 Feb 1994, F. C. T. Lima . MZUSP 43373 , 5 , 15.2-20.2 mm SL, Porto Nacional , left margin of rio Tocantins, 500 meters from bridge, 10º43’S 48º25’W, 9 Jun 1979, E. Bastos . MZUSP 43425 , 4 , 23.5- 31.1 mm SL, Porto Nacional, Belém-Brasília road, 9 Jun 1979, E. Bastos . MZUSP 47864 , 44 , 13.2-35.2 mm SL, Natividade, Ribeirão da Represa, tributary of ribeirão Formiguinha at Fazenda São Judas , approximately 30 km North of Natividade, approximately 11º31’00”S 47º52’00”W, 2-9 Fev 1994, F. C. T. Lima . MZUSP 113722 , 7 , 17.6-34.4 mm SL, Almas, rio do Peixe at bridge on TO-280, 11º40’0.7”S 47º26’19.9”W, 2 Dec 2012, J. Birindelli, F. Dagosta, M. Loeb & C. Santos . MZUSP 113724 , 18 , 17.1-36.3 mm SL, same data as holotype . MZUSP 1131726 , 2 , 29.8-33.6 mm SL, Dianópolis, córrego Gameleira , 11°37’34.8”S 46°56’25.4”W, 2 Dec 2012, J. Birindelli, F. Dagosta, M. Loeb & C. Santos . MZUSP 113727 , 1 , 19.7 mm SL, Dianópolis, rio Mombó at road TO-280, 11°29’53.6”S 46°50’32.3”W, 2 Dec 2012, J. Birindelli, F. Dagosta, M. Loeb & C. Santos . MZUSP 113728 , 1 , 19.1 mm SL, Rio da Conceição, balneário at rio Manoel Alves , 11°24’12.9”S 46°51’30.3”W, 3 Dec 2012, J. Birindelli, F. Dagosta, M. Loeb & C. Santos . ZUEC 6756 , 4 , 27.4-33.6 mm SL, Gurupi-Aliança do Norte road, Fazenda Suely , Jul 1981, J. Pombal-Jr .

Non-type material. CAS (SU) 56087, 4, 22.0- 31.2 mm SL, Brazil, Goiás, “Laguinha II”, Santa Teresa Valley , 6 Jan 1924, C. Ternetz. CAS (SU) 56305, 1, 31.7 mm SL, Brazil, Goiás, “Jausinho brook into rio Tocantins ” (not located), 22 Feb 1924, C. Ternetz .

Diagnosis. Hemigrammus ataktos can be distinguished from all congeners by its unique color pattern, consisting of a black midlateral stripe on body, extending from the posterior margin of the eye to the median caudal-fin rays (vs. dark stripe or thin line extending approximately from the humeral blotch or from the vertical through dorsal-fin origin to the caudal fin). The elongated anteriormost portions of the dorsal, pelvic, and anal

fins in mature males also help to recognize the new species, feature only shared with H. filamentosus Zarske.

Description. Morphometric data presented in Table 1 . Smallsized species, largest examined specimen 37.7 mm SL. Body compressed, moderately elongate. Greatest body depth slightly anterior to dorsal-fin origin. Dorsal profile of head convex from upper lip to vertical through anterior nostril; straight to slightly convex from that point to tip of supraoccipital spine. Dorsal profile of body slightly convex along predorsal region, straight and posteroventrally inclined along dorsal-fin base, straight to slightly convex from terminus of dorsal-fin base to adipose-fin origin, and concave along caudal peduncle. Ventral profile of head and body straight to slightly convex from tip of lower jaw to pectoral-fin origin, convex from that point to anal-fin origin, straight and posterodorsally inclined along anal-fin base, and concave along caudal peduncle.

Jaws equal, mouth terminal. Premaxillary teeth in two rows. Outer row with 2(3), 3(20), or 4*(18) tricuspid, rarely pentacuspid teeth. Inner row with 5*(40) tri- or pentacuspid teeth. Tip of maxilla approximately at vertical through middle of second infraorbital. Maxilla with 1(3), 2*(18), 3(17), 4(3), or 5(1) tri- to pentacuspid teeth. Dentary with 4*(41) large pentacuspid, one smaller tetra- or tricuspid, and series of 6-13 diminute conical, rarely tricuspid, teeth. Central median cusp in all teeth longer than lateral cusps ( Fig. 2 ). Branchiostegal rays 4(11). First gill arch with 1(2), 2(5), or 3(4) rakers on hypobranchial, 9(5) or 10(6) rakers on ceratobranchial, 1(11) raker on intermediate cartilage, and 5(2), 6(8), or 7(1) rakers on epibranchial. Gill rakers with small spines along its length.

Scales cycloid, with four to seven radii on posterior border, and conspicuous circulii anteriorly. Lateral line straight to slightly curved ventrally, with total of 32(2), 33(31), 34(40), 35(24), or 36*(4) scales. Scales on lateral line series variably perforated. Four specimens with 33(2), 34(1), and 35(1) completely pored lateral line; 65 specimens with 6(4), 8(5), 9(11), 10(9), 11(12), 12(8), 13(6), 14(6), or 15(4) pored scales followed by non-pored ones (incomplete lateral line), and 31 specimens with pored scales interspersed with non-pored ones (discontinuous lateral line) of variable pattern. Holotype with 19 pored + 7 non-pored + 2 pored + 1 non-pored + 6 pored lateral-line scales. Longitudinal scale rows between dorsal-fin origin and lateral line 5*(29) or 6(1). Longitudinal scale rows between lateral line and pelvic-fin origin 3*(22) or 4(8). Predorsal scales 10*(21), 11(5), or 12(4), in one series. Single row of 4(2), 5(6), 6*(11), 7(4), or 8(2) scales at base of anteriormost anal-fin rays. Circumpeduncular scale rows 14(30). Caudal fin with small scales along proximal one-fourth of upper lobe and proximal one-half of lower lobe. Supraneurals 4(7) or 5(3), with dorsal portion expanded.

Dorsal-fin rays ii(41), 9*(40) or 10(1). Proximal tip of dorsal-fin pterygiophore inserted posterior to neural spine of 9 th or 10 th vertebra. Base of last dorsal-fin ray at vertical through base of first or second branched anal-fin rays. Pectoral-fin rays i(30), 10(17), 11*(22), or 12(1). Pelvic-fin rays i(41), 7*(41). Adipose-fin origin at vertical through base of 18 th or 19 th branched anal-fin rays. Anal fin falcate, with iv(1), v(9), vi(1), 20(2), 21(6), 22(14), 23*(15), or 24(4) rays. Proximal tip of first anal-fin pterygiophore inserted posterior to haemal spine of 15 th (2) or 16 th (4) vertebra. Caudal-fin with i(39), 9(39) rays on the upper and 8(39), i(39)* rays on the lower lobe. Caudal fin forked, with similar sized lobes. Dorsal procurrent caudalfin rays 10(2), 11(7), or 12(2); ventral procurrent caudal-fin rays 9(9) or 10(1). Total vertebrae 33(4) or 34(3): precaudal vertebrae 14(2) or 15(5) and caudal vertebrae 18(2) or 19(5).

Color in alcohol. Overall ground color light tan. Infraorbital, opercular and gular areas with guanine ( Fig. 1b, c ). Dorsal portion of head dark. Snout, maxilla, and lower jaw scattered with dark chromatophores. Dorsalmost three horizontal scale rows on body with slightly reticulated pattern, formed by dark pigment on middle portion of exposed area of scales. Deep black midlateral stripe on body, extending from posterior margin of eye to median caudal-fin rays. Stripe one-and-ahalf scales deep. Narrow longitudinal dark line at horizontal septum, formed by embedded dark chromatophores, extending approximately from vertical through dorsal-fin origin to end of caudal peduncle. Scattered dark chromatophores above anal-fin base. All fins with dark chromatophores along edge of lepidotrichia. Distal margin of third to fifth branched dorsal fin-rays and smallest branched anal-fin rays dark.

Color in life. Dorsal portion of body yellowish tan above black midlateral stripe ( Fig. 1a ). Opercular area and ventral portion of body below black midlateral stripe with guanine. Narrow bright yellow line above black midlateral stripe. Black midlateral stripe over middle portion of eye. Dorsal portion of eye red, ventral portion silver. Tip of dorsal, pelvic, and anal fins creamy white. Adipose fin, most of dorsal and pelvic fins, and proximal portion of anteriormost rays of anal fin yellow. Proximal two-thirds of caudal-fin lobes red on mature males (no information available for females and juveniles).

Sexual dimorphism. Mature males with dorsal (31.6-44.9% of SL), pelvic (18.8-23.8% of SL) and anal fin (23.1-27.3% of SL) longer than females or immatures (28.1-32.9%; 15.8- 20.3%; 19.5-24.4%, respectively) ( Table 1 , Fig. 3 ). Tip of pelvic fin extending from base of first to fifth branched analfin ray in mature males and not reaching anal fin or extending to base of first branched anal-fin ray in females. Bony hooks were not observed on fins of any analyzed specimen.

Geographic distribution. Hemigrammus ataktos is known from middle rio Tocantins basin, from rio Santa Tereza , Goiás State, from the rio Manoel Alves basin, and from smaller tributaries of the rio Tocantins immediately downstream of the mouth of rio Manoel Alves, Tocantins State, Brazil ( Fig. 4 ) .

Etymology. From the Greek ataktos , meaning disordered or irregular, in allusion to the variation in the perforation of lateral-line scales present in the new species. An adjective.

Figures

Fig. 1. Hemigrammus ataktos, holotype, MZUSP 113725, 37.7 mm SL, male (a) photographed alive, (b) after preservation; (c) MZUSP 113724, paratype, 33.0 mm SL, female, rio ManoelAlves drainage, rioTocantins basin, Natividade,Tocantins State, Brazil.

Fig. 2. Medial view of left side, upper and lower jaws of Hemigrammus ataktos, MZUSP 47846, paratype, 33.7 mm SL. Scale bar = 1 mm.

Fig. 3. Fin lengths as function of standard length in males (dark diamonds) and females (light squares) of Hemigrammus ataktos: (a) dorsal fin, (b) pelvic fin, and (c) anal fin. Remarks. Specimens from CAS collection were designated as non-type material due to their poor condition.

Fig. 4. Distribution of Hemigrammus ataktos in the middle rio Tocantins basin, central Brazil. Type locality represented by red circle.