Astyanax douradilho, Bertaco, Vinicius A., 2014

Bertaco, Vinicius A., 2014, Astyanax douradilho, a new characid fish from the rio Tramandaí system, southern Brazil (Characiformes: Characidae), Zootaxa 3794 (3), pp. 492-500 : 493-497

Astyanax douradilho , new species

( Figs. 1–2 , Table 1 )

Holotype. MCN 19858, 1, 90.0 mm SL, Brazil, Rio Grande do Sul State, municipality of Maquiné, Barra do Ouro District, rio Maquiné basin, rio Tramadaí system, arroio Encantado, 29º36’28”S 50º12’15”W, 1 Nov 2013, V.A. Bertaco, M.A. Azevedo, C.L. Castilho & A.C. Vigo.

Paratypes. Brazil, Rio Grande do Sul State, municipality of Maquiné, Barra do Ouro District, rio Maquiné basin, rio Tramadaí system. MCN 19895, 10, 51.3-72.7 mm SL, UFRGS 18390, 7, 60.5-65.5 mm SL, rio do Ouro, 29º35’12”S 50º17’00”W, 16 Dec 2010, C. Vogel, G. Rosa & L. Artioli. MCN 19896, 6, 63.7-76.0 mm SL, rio do Ouro, 29º35’12”S 50º17’00”W, 11 Jan 2011, C. Vogel, R. Paesi & G. Rosa. MCP 25371, 2, 57.1–58.3 mm SL, arroio Encantado, 29º36’28”S 50º12’15”W, 1 Sep 1999, F.G. Becker, M. Vassiliou & G. Irgang. MCP 25479, 2, 68.6–72.0 mm SL, arroio Encantado, 29º36’28”S 50º12’15”W, 31 Aug 1999, F.G. Becker, M. Vassilou & T. Finkler. MCP 25692, 1, 73.9 mm SL, arroio Lageado (Cerrito), 29º34’16”S 50º16’51”W, 4 Sep 1999, F.G. Becker, G. Irgang & M. Vassiliou. MCP 25693, 2, 59.6–67.4 mm SL, arroio Forqueta, 29º32’42”S 50º14’21”W, 23 Feb 2000, F.G. Becker, F.S. Villela, M.F. Corrêa & C.S. Villela. MCP 25698, 3, 63.7–75.2 mm SL, arroio Forqueta, 29º32’42”S 50º14’21”W, 26 Feb 2000, F.G. Becker, F.S. Villela, M.F. Corrêa & C.S. Villela. MCP 25700, 12 (3 c&s), 46.0– 70.5 mm SL, arroio Encantado, 29º36’28”S 50º12’15”W, 26 Feb 2000, F.G. Becker, F.S. Villela, M.F. Corrêa & C.S. Villela. MCP 25708, 2, 48.4–60.0 mm SL, arroio Encantado, 29º36’28”S 50º12’15”W, 22 Jan 2000, F.G. Becker, F.S. Villela, M.F. Corrêa & M.B. Fonseca.

Diagnosis. Astyanax douradilho differs from all congeners inhabiting the rio Uruguay basin, laguna dos Patos and rio Tramandaí systems by the presence of 3–5 maxillary tricuspid teeth, except from A. henseli Melo & Buckup , A. laticeps (Cope) , and A. paris Azpelicueta, Almirón & Casciotta , and by the absence of a conspicuous dark stripe from humeral region to caudal peduncle. Additionally, it differs from A. henseli by the number of gill rakers on lower branch of first arch (11–12 vs. 15–19), from A. laticeps by the number and shape of humeral spots (two vertically elongate vs. one oval horizontally elongate), and from A. paris by the number of perforated scales along the lateral line (37–39 vs. 34–36). The following combination of characters distinguishes A. douradilho from all other species of the genus: the presence of two vertically elongate humeral spots, a conspicuous caudal spot, absence of a conspicuous dark stripe from humeral region to caudal peduncle, 3–5 maxillary tricuspid teeth, 22–24 branched anal-fin rays, 3 7 –39 perforated scales along the lateral line, head length (26.0–29.9% SL), upper jaw length (43.8–50.6% HL), and snout length (23.0–28.6% HL).

Description. Morphometric data summarized in Table 1 . Body compressed and elongate, with greatest body depth anterior to dorsal-fin origin. Dorsal profile of head straight or slightly convex. Dorsal body profile convex from tip of supraocciptal spine to base of last dorsal-fin ray; straight from that point to adipose fin origin. Ventral profile of body convex from mandibular symphisis to pelvic fin origin, nearly straight to anal-fin origin, and posterodorsally slanted along anal-fin base. Caudal peduncle deep, nearly straight on dorsal and ventral margins.

Snout rounded from margin of upper lip to vertical through anterior nostrils. Head somewhat pointed anteriorly in lateral profile. Mouth terminal, jaw isognathous. Mouth slit nearly at horizontal through the middle of eye. Maxilla extending posteriorly to vertical through anterior margin of orbit reaching pupil. Maxilla widened anteroposteriorly.

Premaxillary teeth in two rows: outer row with 4(24), 5(9), or 6*(2) tricuspid teeth, central cusp longer; inner row with five teeth, gradually decreasing in length from first to fifth; usually with four cusps on first tooth, five cusps on second to fourth teeth and three cusps on fifth tooth. Maxilla with 3(27), 4*(7), or 5(2) tricuspid teeth; central cusp broader than others. Dentary with 3(2) or 4*(28) large tri- or pentacuspid teeth, followed by six to eight small teeth, uni- to tretracuspid ( Fig. 2 ). Median cusp in all cuspidate teeth longer than remaining cusps; cusp tips slightly curved inwardly in dentary, premaxillary teeth cusps approximately straight.

Dorsal-fin rays i,9(1) or 10*(34); first unbranched ray approximately half length of second ray. Distal margin of dorsal fin nearly straight to somewhat convex. Dorsal fin origin slightly behind middle of SL. Origin of adipose fin at vertical through second or third last anal-fin rays. Anal-fin rays iii(20) or iv(16), 22(11), 23*(16), or 24(8). Anal fin origin posterior to vertical through base of last dorsal-fin ray. Pectoral-fin rays i,11(2), 12(14), 13*(14), or 14(6). Pectoral-fin tip not reaching pelvic-fin insertion. Pelvic-fin rays i,7*(36). Pelvic fin origin slightly anterior to vertical through dorsal-fin origin. Caudal fin forked, lobes similar in size, i,17,i*(34) principal rays. Dorsal procurrent rays 11(1), 12(1), or 13(1) and ventral procurrent rays 10(2) or 11(1).

Lateral line complete with 37(13), 38*(18), or 39(5) scales. Scale rows between dorsal-fin origin and lateral line 6(6) or 7*(30); scale rows between lateral line and pelvic-fin origin 5*(31) or 6(5). Predorsal scales 11(9), 12*(21) or 13(4) arranged in regular series. Scale rows around caudal peduncle 14(9), 15(11), or 16*(15). Scale sheath along anal fin base 8-15 scales (32), in single series, covering base of anteriormost rays. Axillary scale, longer than wide, relatively folded in half, and extending over 1-2 longitudinal scale series.

Precaudal vertebrae 15(1), 16(1), or 17(1); caudal vertebrae 20(2) or 21(1); total vertebrae 36(2) or 37(1). Supraneurals 5(3). Gill-rakers upper branch 6(8) or 7(6); lower branch 11(8) or 12(6); total number 17(3), 18(10), or 19(1).

Color in alcohol. Dorsal and dorsolateral portions of head and body dark brown. Infraorbital and opercular areas covered with scattered, dark chromatophores. Scales on lateral body with dark brown chromatophores. Midlateral stripe very faint. Caudal spot black, triangular or irregular in shape, extending to tip of middle caudal-fin rays. Two humeral spots. Anterior one, conspicuous, vertically elongate with upper portion wider, located over third to fifth vertical series of scales, extending over 2 to 3 horizontal series of scales above lateral line; lower portion of spot narrow (1 to 2 scales pigmented), extending over 1 to 2 horizontal series of scales below lateral line. Second humeral spot large, occasionally faint, not surpassing lateral line ventrally, extending over 3 horizontal series and 2 to 3 vertical series of scales above lateral line. Scattered dark chromatophores on dorsal, adipose, caudal and anal fins. Pectoral and pelvic with few dark chromatophores. Dark pigmentation on middle caudal-fin rays and along median-distal portion of anal-fin rays ( Fig. 1 a).

Color in life. Color pattern similar to that described for alcohol preserved specimens. Overall and head color pattern yellowish, slightly brown. Dorsolateral portion of body dark gray. Scales on lateral body silvery. Dorsal, pectoral, and pelvic fins with anterior portion yellowish and posterior reddish. Anal fin reddish colored at distal half of first rays. Caudal fin almost completely reddish, except middle portion. Adipose fin yellowish ( Fig. 1 b).

Sexual dimorphism. Males with small bony hooks on dorsal-, pectoral-, pelvic- and anal-fin rays (rarely in caudal-fin). One paired bony hook per lepidotrichia in the last unbranched anal-fin ray and first to thirteenth branched anal-fin rays on median and distal portions of the rays. One paired bony hook per lepidotrichia on second to fifth branched pelvic-fin rays. Small bony hooks on distal one-third of anteriormost branched dorsal- and pectoral-fin rays, and on distal portion of middle caudal-fin rays. No other apparent sexually dimorphic features were found in the specimens examined. Gill glands ( Burns & Weitzman 1996) were not found macroscopically on the first gill arch.

Distribution. Astyanax douradilho is known from tributaries of the rio Maquiné, rio Tramandaí system, coastal drainage of Rio Grande do Sul, southern Brazil ( Fig. 3 ).

Etymology. Douradilho is a regional name for the horse color pattern consisting of a reddish brown or golden yellow. The name is an allusion to the color of the fins in live specimens. A noun in apposition.

Ecological notes. Astyanax douradilho was collected in relatively small, clear water streams until 1 m deep, with stones and rocks on bottom, and moderate riparian vegetation. The collection localities are around 300 m above sea level. In the Encantado ( Fig. 4 ) and Lageado streams, the pH ranged from 6.5 to 6.8, conductivity between 31.7 to 39.5 µs/cm, and oxygen level between 5.0 to 6.8 mg /l. Based on examination of several lots in fish collection, the species seems to be found only in mainstream of small rivers draining from Serra Geral formation, and was not found in the other subregion basin formed by lagoons of the Coastal Plain ( Malabarba & Isaia 1992).

Figures

FIGURE 1. Astyanax douradilho, MCN 19858, 90.0 mm SL, holotype, arroio Encantado, rio Maquiné basin, rio Tramandaí system, municipality of Maquiné, Rio Grande do Sul State, Brazil. A) Specimen just after fixation; B) in alcohol.

FIGURE 2. Astyanax douradilho, MCP 25700, 54.0 mm SL, paratype. Upper and lower jaw teeth, left side, lateral view. Scale bars = 1 mm.

FIGURE 3. Map of southern Brazil showing the distribution of the examined material of Astyanax douradilho. Some symbols represent more than one lot or locality. T = type locality.

FIGURE 4. Type locality of Astyanax douradilho, arroio Encantado, rio Tramandaí system, municipality of Maquiné, Rio Grande do Sul State, Brazil.

Tables

TABLE 1. Morphometric data for holotype and paratypes of Astyanax douradilho, n. sp., n = 30 (including holotype) from the rio Maquiné drainage, rio Tramandaí system, Rio Grande do Sul, Brazil. SD = Standard Deviation.

	Holotype	Range	Mean	SD
Standard length (mm)	90.0	48.4–90.0	65.3	–
Percents of Standard length
Predorsal distance	52.8	52.0–57.0	54.6	1.3
Prepelvic distance	48.5	47.2–51.5	49.2	1.1
Prepectoral distance	27.4	25.8–30.2	27.8	1.0
Preanal distance	67.5	64.6–69.6	67.3	1.3
Depth at dorsal-fin origin	35.9	34.4–41.0	37.0	1.3
Caudal peduncle depth	12.4	11.6–13.4	12.3	0.4
Caudal peduncle length	12.6	9.5–14.0	11.6	1.3
Anal-fin base length	28.6	26.7–30.6	28.5	1.0
Dorsal-fin length	26.2	26.2–30.6	28.3	1.1
Pelvic-fin length	17.4	14.1–19.1	17.9	1.0
Pectoral-fin length	21.9	21.9–25.3	23.4	0.8
Head length	26.2	26.0–29.9	27.7	1.2
Percents of Head length
Snout length	25.6	23.0–28.6	26.0	1.6
Upper jaw length	50.5	43.8–50.6	47.5	1.7
Orbital diameter	34.5	34.2–40.7	38.0	2.0
Interorbital width	28.5	22.6–30.0	27.1	1.6