Astyanax taurorum, de Lucena & Zaluski & Lucena, 2017

de Lucena, Carlos Alberto S., Zaluski, Amanda Bungi & Lucena, Zilda Margarete Seixas de, 2017, Astyanax taurorum a new species from dos Touros River, Pelotas River drainage, an upland southern Brazilian river (Characiformes: Characidae), Zoologia (e 20174) 34, pp. 1-8 : 2-6

Astyanax taurorum sp. nov.

http://zoobank.org/ F15C02B5-AF1B-4052-A67A-741560E1468F

Fig. 1, Table 1

Types series. Brazil, Rio Grande do Sul, Bom Jesus. Holotype: Tributary of dos Touros River ca. 4 km northeastern of the road BR-285, Pelotas River drainage, 1,056 m a.s.l., 28°41’06”S 50°12’51”W, 12 Feb 2016, J. Pezzi da Silva and E. Pereira leg., MCP 49468 , 80.7 mm SL. Paratypes: Tributary of dos Touros River , on the road Silveira-Rondinha, ca. 28°39’08”S 50°18’25”W, 14 Jan 1989, C. Lucena, P. Azevedo and E. Pereira leg., MCP 14370 , 20 (17, 22.2-82.6 mm SL, 3 c&s, 29.6–62.6 mm SL). Same locality of MCP 14370 , MZUSP 120697 , 1 , 29.9 mm SL. Dos Touros River , dowstream dam, Pelotas River drainage, road Rondinha – Silveira, 998 m a.s.l., 28°38’44”S, 50°17’06”W, 12 Feb 2016, J.P. Silva and E. Pereira leg., MCP 49467 , 1 , 75.7 mm SL .

Diagnosis. Astyanax taurorum sp. nov. belongs to the A. scabripinnis species complex and is distinguished from the species of that complex by having two humeral spots (vs. one in A. courensis Bertaco, Carvalho & Jerep, 2010 , A intermedius Eigenmann, 1908 , A. jenynsii (Steindachner, 1877) , A. jordanensis Vera Alcaraz, Pavanelli & Bertaco, 2009 , A. laticeps (Cope, 1894) , A. microschemos Bertaco & Lucena, 2006 , A. serratus Garavello & Sampaio, 2010 , A. totae Haluch & Abilhoa, 2005 , A. rivularis and A. varzeae Abilhoa & Duboc, 2007 ); 20–23 total gill rakers in first branchial arc (vs. 16 in A. jacobinae Zanata and Carmelier, 2008 , 16–17 in A. gymnogenys Eigenmann, 1911 , 18 in A. burgerai Zanata & Carmelier, 2009 , 17–18 in A. troya Azpelicueta, Casciotta & Almirón, 2002 , 18–19 in A. epiagos Zanata & Carmelier, 2008 , 17–19 in A. ojiara Azpelicueta & Garcia, 2000 , A. cremnobates Bertaco & Malabarba, 2001 and A. leonidas Azpelicueta, Casciotta & Almirón, 2002 ); 13–15 gill rakers on the lower branch of the first branchial arch (vs. 9–10 in A. turmalinensis Triques, Voino & Caiafa, 2003 ); 33–36 perforated lateral line scales (vs. 39–41 in A. gymnogenys and A. eremus Ingenito & Duboc, 2014 , 40–43 in A. guaricana Oliveira, Abilhoa & Pavanelli, 2013 ); 20–23, usually 21 or 22, branched anal-fin rays (vs. 18–19 in A. burgerai , 13–16 in A. goyanencis Miranda Ribeiro, 1944 , 16–20, usually 16 or 17 in A. serratus Garavello & Sampaio, 2010 , 14–18 in A. microschemos , 15–18 in A. totae , 12–16 in A. brachypterychium , 14–18 in A. cremnobates , and 13–17 in A. epiagos and A. jordanensis ); inner row of premaxilla with teeth bearing three to five cusps (vs. heptacuspid in A. ita Almirón, Azpelicueta & Casciotta, 2002 and A. pirabitira Lucena, Bertaco & Berbigier, 2013 ); 2–3 maxillary teeth (vs. 1 in A. obscurus Hensel, 1870 , A. ojiara , A. troya Azpelicueta, Casciotta & Almirón, 2002 , A. guaricana , A. courensis and A. ita Almirón, Azpelicueta & Casciotta, 2002 ; 0–1 in A. pirapuan Tagliacollo, Britzke, Silva & Benine, 2011 ); length of anal-fin base 23.6–28.0% (mean = 26.3%) of SL (vs. 19.8–24.3% (mean = 21.5%) of SL in A. eremus and 30.2% in A. scabripinnis Jenyns, 1842 in the holotype); body depth 33.8–37.6% of SL (vs. 26.9–29.7% in A. microschemos , and 27.3–31.3% in A. eremus ); head length 29.0–30.5% of SL (vs. 22.9–25.1% in A. gymnogenys , 21.9–27.1% in A. courensis , 26.6–28.2% in A. turmalinensis , and 23.9–26.6% of SL in A. guaricana ); eye diameter 29.0–32.4% of HL (vs. 24.4–26.1% in A. gymnogenys , and 36.8–40.3% in A. jacobinae ); snout length 23.8–28.8% of HL (vs. 16.0–20.4% in A. paranae ); and interorbital length 24.7–28.0% of HL (vs. 35.2–37.8% in A. gymnogenys , 29.6–37.3% in A. jacobinae , 30.4–34.5% in A. goyanensis , 37.5–47.1% in A. intermedius , 29.8–37.7% in A. varzea , 32.7–40.9% in A. guaricana , 30.6–35.7% in A. jordanensis , 40.7% in A. scabripinnis holotype), and 31.7–39.2% in A. pirapuan ). Within the Astyanax scabripinnis complex, Astyanax taurorum sp. nov. is most similar to A. paris Azpelicueta, Almirón & Casciotta, 2002 – species known from the type locality, Arroio Fortaleza, tributary of upper Uruguay River, Argentina – with which most counts and morphometric percentages overlap. Nevertheless, Astyanax taurorum sp. nov. differs from A. paris by the presence of hooks on branched anal-fin rays (vs. secondary sexual dimorphism absent in A. paris ), interorbital width 24.7–28.0% HL (vs. 28.4–32.8% HL) and head depth 73.6–86.7% HL (vs. 86.4–96.6% HL) ( Fig. 2) ( Table 2), and by having posterodorsal margin of the posttemporal hook-shaped ( Fig. 3) (see Discussion). Astyanax taurorum sp. nov. is distinguished from the other species in the genus by the following combination of characters: presence of two conspicuous humeral spots, the first one vertically elongated with the upper portion enlarged, but narrowing ventrally; dark midlateral horizontal stripe; conspicuous caudal spot extending posteriorly to the middle of caudal-fin rays; 20–23 branched anal-fin rays; 20–23 total gill rakers in first branchial arc; 33–36 perforated lateral line scales; 5–7 scale rows between lateral line and pelvic-fin origin; outer row of premaxilla with tricuspid teeth; teeth in inner row of premaxilla with three to five cusps; 2–3 tricuspid teeth in the maxilla, head length 29.0–30.5% of SL; body depth 33.8–37.6% of SL; interorbital width 24.7–28.0% of HL; eye diameter 29.0–32.4% of HL, and length of anal-fin base 23.6–28.0% of SL.

Description. Morphometric data summarized in Table 1. Body compressed and moderately elongate, greatest body depth at vertical through near middle length of pectoral fin. Dorsal profile of head convex from tip of snout to vertical through nostrils, straight from that point to vertical through posterior border of orbital, slanted until tip of supraoccipital spine. Snout relatively slender. Dorsal profile of body convex from tip of supraoccipital bone to dorsal-fin origin; straight from that point to end of caudal peduncle. Ventral body profile convex from mandibular symphysis to pelvic-fin origin, nearly straight from that point to anal-fin origin, and slanted along anal-fin base. Dorsal and ventral profiles of caudal peduncle nearly straight.

Mouth terminal or slightly subterminal, slit below horizontal passing through middle of eye. Posterior tip of maxilla extending between vertical through anterior margin of orbit and the vertical through middle of orbit.Two tooth rows in premaxilla; outer row with 3*(2), 4(13), or 5(5) tricuspid teeth; inner row with five teeth, usually bearing four cusps on first tooth, five cusps on second to fourth tooth, three cusps on fifth tooth.Maxilla with 2(8) or 3(8) tricuspid teeth. Dentary with four large pentacuspid teeth, followed by seven small tricuspid teeth and one conical tooth (two c&s). Median cusp in all cuspidate teeth longer than remaining cusps; cusp tips slightly curved inwardly on dentary ( Fig. 4).

Dorsal-fin rays ii, 9 (23); first unbranched ray short, onehalf length of second ray. Distal margin of dorsal fin slightly convex. Dorsal-fin origin slightly behind middle of SL. Adipose-fin origin at vertical through base of fifth or sixth last anal-fin rays. Anal-fin rays iii-iv 20(2), 21(6), 22(9), or 23(4). Anal-fin origin posterior to vertical through base of last dorsal-fin ray. Pectoral-fin rays i, 11(1), 12(7), 13(11), or 14(1). Tip of pectoral-fin tip ending one scale before or, occasionally, reaching pelvic-fin insertion. Pelvic-fin rays i, 7(23), tip of fin not reaching anal-fin origin. Axillary scale present.

Caudal-fin forked, lobes similar in size.

Lateral line complete with 33(2), 34(2), 35(8), or 36(5) perforated scales. Scale rows between dorsal-fin origin and lateral line 6(5) or 7(12); scale rows between lateral line and pelvic-fin origin 5(5), 6(13), or 7(1); scale rows between lateral line and anal-fin origin 5(1), 6(15), or 7(1); scale rows around caudal peduncle 14 (8), 15(5), or 16(2).

Precaudal vertebrae 13 (3); caudal vertebrae 18(2) or 19(1); total vertebrae 31(2) or 32(2). Supraneurals 5(3). Gill rakers on upper branch 6(1), 7(11) or 8(11) and on lower branch 13(7), 14(14), or 15(2) in first branchial arch; total gill rakers in first branchial arch 20(3), 21(13), 22(6), or 23(1).

Color in alcohol. Dorsal and dorsolateral portions of head and body dark brown. Scales on lateral of body with dark brown chromatophores sometimes concentrated on anterior border. Two conspicuous humeral spots. Anterior humeral spot vertically elongate with upper portion wider, located on second to third or fourth scale vertical series, extending three horizontal scale series above lateral line; lower portion narrow, extending on the lateral line and one or two horizontal scale series below it. Posterior humeral spot large, absent in small specimens (22.8–29.4 mm SL), reaching but not surpassing lateral line ventrally, extending on two or three horizontal scale series and three vertical scale series. Humeral spots separated by a clear area occupying two or three vertical scale series. Dark midlateral strip inconspicuous anteriorly, but conspicuous posteriorly from about vertical through middle of dorsal-fin base to caudal peduncle; absent in small specimens (22.8–29.4 mm SL). Caudal peduncle spot triangular, extending over median caudal-fin rays. Scattered dark chromatophores on dorsal, anal, and caudal fins. Pectoral and pelvic-fins hyaline or covered by sparse dark chromatophores.

Color in life. Overall body olive green, silvery below lateral line. Humeral spots and caudal peduncle spot conspicuous. Dorsal, anal, pelvic and caudal fins reddish. Pectoral-fin yellowish. Dark brown blotches located on anterior portion of scales.

Sexual dimorphism. Hooks on anal-fin rays of four specimens with 75.4 to 80.6 mm SL ( MCP 14370 ). Hooks short, conical or slightly retrorse found on the first or third to eighth branched rays, along the posterolateral margin of the posterior branch. One pair on each segment. One specimen with a single hook on the third branched anal-fin ray and another specimen with a very small hook on the first branched ray and small protuberances on other rays .

Distribution and habitat. Astyanax taurorum sp. nov. is known from the dos Touros River drainage, tributary of Pelotas River, which in turn is a tributary of Uruguay River ( Fig. 5). The Pelotas River drainage is located in the region named “Campos de Altitude do Planalto das Araucárias (= Araucaria Plateau in Bertaco et al. 2016)” or “Campos de Cima da Serra”, which has a high level of endemism of fishes ( Malabarba et al. 2009, Bertaco et al. 2016: 430) and other groups of animals (for example: sponges, Ribeiro et. al. 2009; crustaceans, Bond-Buckup et al. 2009). The dos Touros River tributary, type locality of Astyanax taurorum sp. nov., has a low to medium flow, transparent waters with stones and rocks on the bottom and moderate emergent marginal vegetation ( Fig. 6). Four characid species were caught along with Astyanax taurorum sp. nov.: Bryconamericus patriciae Silva, 2004 , B. iheringi Boulenger, 1887 , Cheirodon interruptus Jenyns, 1842 , and Oligosarcus brevioris Menezes, 1987 .

Etymology. The specific name taurorum , is derived from the Latin masculine noun taurus (second declension, meaning bull) inflected in the plural and genitive case. Therefore taurorum means “of the bulls” in reference to “rio dos Touros“ (= Portuguese, which means “river of the bulls”) the type locality.

Conservation status. Astyanax taurorum sp. nov. is likely rare and occurs in low densities. All type specimens were collected in the dos Touros River drainage, during two field trips in 1989 and 2016. Over the last four decades (from 1980 to 2016), six field trips to the dos Touros River system have been conducted by the MCP team, two of which with the sole purpose of collecting specimens of A. taurorum . Unfortunately, no specimens were collected in 2015, and only two were found in 2016. The Museu de Ciências Naturais (FZB, Porto Alegre) and Universidade Federal do Rio Grande do Sul also conducted field surveys in that region, but no specimens of A. taurorum sp. nov. were obtained. Despite the reduced number of specimens collected and the apparently restricted geographical distribution of the new species, we did not assign Astyanax taurorum sp. nov. to any threat category because we the lack biology data for it. Instead, we considered A. taurorum sp. nov. as data deficient (DD) ( IUCN 2014).

Additional material. Types: Argentina: Astyanax paris, MNHG 2623.065 paratypes, 3 (70.3–73.1 mm SL), arroio Fortaleza. MCP 34461 topotypes, 5 (4, 66.9–73.5 mm SL, 1 c&s 68.2 mm SL). Astyanax troya, MCP 28438 paratypes. All c&s specimens: Types: Brazil: Astyanax cremnobates , paratypes MCP 11650 (2); Astyanax dissensus , paratypes MCP 17361 and MCP 47518 (1); Astyanax douradilho , paratypes MCP 25700 (3); Astyanax elachylepis , paratype MCP 16054 (1); Astyanax eremus , paratypes MCP 46942 (1); Astyanax jordanensis , paratype MCP 41915(1); Astyanax microschemos , paratype MCP 34366 (1); MCP 19783 (5); Astyanax pelecus , paratype MCP 17919 (1); Astyanax pirabitira , paratypes MCP 14390 (6); Astyanax utiariti , paratypes MCP 40041 (3); Astyanax procerus , paratype MCP 25513 (1); Astyanax xiru , paratype MCP 21730 (1). Non-types: Astyanax lacustris, MCP 20339 (1); Astyanax eigenmanniorum MCP 25122 (1); Astyanax henseli MCP 48121 (3); Astyanax aff fasciatus MCP 21627 (1); Astyanax laticeps, MCP 25690 (1), MCP 17614 (1), MCP 27619 (2); Astyanax obscurus MCP 26125 (2)); Astyanax saguazu MCP 16808 (1), and MCP 4000 (3); Astyanax sp. UFRGS 14052 (6), UFRGS 14051 (6) and UFRGS 14055 (6); Hyphessobrycon anisitsi MCP 21633 (2); Markiana nigripinnis MCP 17086 (1).