Astyanax bagual, Bertaco & Vigo, 2015

Bertaco, Vinícius A. & Vigo, Anelise C., 2015, A new species of Astyanax Baird & Girard (Ostariophysi: Characidae) from the rio Taquari-Antas basin, southern Brazil, Neotropical Ichthyology (Neotrop. Ichthyol.) 13 (2), pp. 265-272 : 266-269

Astyanax bagual , new species

ur n:lsid:zooban k.org:act: 119C81F9-A288- 442A-94CF- 87EDDF25D095

Figs. 1-2

Astyanax sp.4.- Becker et al. (2013: 82, table 1, listed, rio Taquari- Antas basin).

Holotype. UFRGS 19525 , 74.1 mm SL, male, Brazil, Rio Grande do Sul State, Dois Lageados, rio Carreiro downstream to hydroeletric plant PCH Linha Emília , rio Taquari-Antas basin, rio Jacuí drainage, laguna dos Patos system, 28º56’30”S 51º46’30”W, 26 Jun 2013, J. Ferrer & J. M. Wingert.

Paratypes. All from Brazil, Rio Grande do Sul State, rio Taquari-Antas basin, rio Jacuí drainage, laguna dos Patos system: MCN 16547, 1, 56.0 mm SL, rio Forqueta , Pouso Novo , 29º05’40”S 52º12’44”W, 13 Jan 2002, P. C. C. Milani. MCN 19903, 1 , 71.1 mm SL, rio Turvo, André da Rocha , 28º36’27”S 51º23’51”W, 9 Jan 2014, A. R. Cardoso & G. Rosa. MCN 19915, 3 , 67.6-73.2 mm SL, collected with holotype . MCP 33552, 1 , 59.2 mm SL, rio das Antas, Santa Bárbara , 29º05’29”S 51º42’42”W, 28 Sep 2002, ichthyology staff MCP. MCP 33620, 2 , 63.0-66.0 mm SL, rio das Antas, Santa Bárbara , 29º05’29”S 51º42’42”W, 6 Nov 2002, J. D. Latini. MCP 33623, 1 , 62.7 mm SL, rio das Antas, Nova Roma do Sul , 29º00’40ºS 51º22’22ºW, 18 Jan 2003, J. D. Latini. MCP 33640, 1 , 65.0 mm SL, rio das Antas, Nova Roma do Sul , 29º00’40ºS 51º22’22”W, 1 Oct 2002, J. D. Latini. UFRGS 6398 , 9 , 56.0- 78.4 mm SL, rio Carreiro , Serafina Corrêa , 28º43’40”S 51º50’56”W, 5 Oct 2003, J. A. Anza & F. S. Villela. UFRGS 6966 , 4 , 63.3-76.8 mm SL, rio Carreiro, Guaporé, Oct 2003 to Jan 2005, J. A. Anza. UFRGS 8958 , 3 , 46.6-54.4 mm SL, rio Carreiro near to hydroeletric plant PCH Linha Emília, Dois Lageados , 28º56’30”S 51º46’30”W, 2 Oct 2006, J. Ferrer & C. E. Machado. UFRGS 10437 , 1 , 74.1 mm SL, rio da Prata near mouth of arroio Jararaca, Nova Roma do Sul , 28º56’30”S 51º26’30”W, 10 Sep 2008, J. Ferrer & G. L. Frainer. UFRGS 12295 , 1 , 68.1 mm SL, rio Carreiro , Guaporé , 28º51’08”S 51º49’57”W, 12 Mar 2012, J. Ferrer & J. M. Wingert. UFRGS 12296 , 6 , 63.1 -72.0 mm SL, rio Carreiro downstream to PCH Linha Emília, Dois Lajeados , 28º56’35”S 51º46’05”W, 10 Mar 2010, J. Ferrer & J. M. Wingert. UFRGS 13733 , 1 , 61.5 mm SL, rio Carreiro , Guaporé , 28º51’08”S 51º49’57”W, 29 Sep 2010, V. A. Bertaco & G. Rosa. UFRGS 17834 , 7 (3 c&s), 65.0- 78.4 mm SL (+2 ethyl alcohol anhydrous), collected with holotype .

Diagnosis. Astyanax bagual differs from all congeners inhabiting the rio Uruguay basin, laguna dos Patos and rio Tramandaí systems by the following characters: first humeral spot vertically elongate with upper portion wider than lower portion and slightly directed forward (vs. presence of oval spot with two brown vertical bars in humeral region in A. jacuhiensis (Cope) , oval spot in A. laticeps (Cope) , and forming a uniform wedge in A. eigenmanniorum (Cope) , A. henseli Melo & Buckup , A. saguazu Caciotta, Almirón & Azpelicueta and A. stenohalinus (Messner) ; two humeral spots (vs. one in A. eigenmanniorum , A. aff. fasciatus (Cuvier) , A. jacuhiensis , and A. laticeps ), 24-28 branched anal-fin rays (vs. 18 or less in A. brachypterygium Bertaco & Malabarba and A. cremnobates Bertaco & Malabarba , 18- 23 in A. procerus Lucena, Castro & Bertaco and A. xiru Lucena, Castro & Bertaco , 20-22 in A. paris Azpelicueta, Almirón & Casciotta , 16-21 in A. obscurus (Hensel) , 15- 23 in A. laticeps , 15-20 in A. pirabitira Lucena, Bertaco & Berbigier , 20-23 in A. ojiara Azpelicueta & Garcia ; 22-24 in A. douradilho Bertaco ); 2-4 maxillary tricuspid teeth (vs. one in A. aramburui Protogino, Miquelarena & López , A. dissensus Lucena & Thofehrn , and A. aff. fasciatus ); 37-39 perforated scales along the lateral line (vs. 34-36 in A. paris ), and 14 scale rows around caudal peduncle (vs. 15-16 in A. stenohalinus ). Furthermore, A. bagual differs from A. douradilho and A. saguazu by body depth (37.9-45.9% of SL, mean = 43.3% vs. 34.4- 41.0% of SL, mean = 37.0% and 30.9-39.0% of SL, mean = 35.6%); and from A. saguazu and A. stenohalinus by preanal distance (62.4-69.1% of SL, mean = 65.5% vs. 56.0-61.2% of SL, mean = 58.7% and 58.2-62.7% of SL, mean = 59.8%), respectively; and from A. stenohalinus by the anal-fin origin located at vertical through last dorsal-fin ray insertions vs. before a vertical through last dorsal-fin ray insertions. The following combination of characters distinguish A. bagual from all others species of the genus (including the species complex A. bimaculatus Linnaeus and A. scabripinnis Jenyns ): the presence of two vertically elongated humeral spots (the anterior humeral spot with upper portion wider than lower portion and slightly directed forward), 24-28 branched anal-fin rays, 37-39 perforated lateral line scales, outer row of premaxilla with tricuspid teeth, inner premaxilla row with pentacuspid teeth, 2-4 maxillary tricuspid teeth, small bony hooks on all fins of mature males, conspicuous caudal peduncle spot, body depth (37.9-45.9% of SL), preanal distance (62.4-69.1% of SL), anal-fin base length (29.7-35.6% of SL), and orbital diameter (29.5-38.2% of HL).

Description. Morphometric data summarized in Table 1 . Body compressed and moderately deep, with greatest body depth anterior to dorsal-fin origin. Dorsal profile of head strongly convex from tip of snout to vertical through nostrils, straight to slightly concave from that point to tip of supraoccipital spine. Dorsal profile of body convex from tip of supraoccipital spine to base of last dorsal-fin ray; straight from thatpoint to adipose fin origin. Ventral profile of body convex from mandibular symphysis 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.

Mouth terminal, isognathous jaw. Mouth slit nearly at horizontal through middle of eye. Maxilla extending posteriorly to vertical through anterior margin of orbit, reaching pupil. Premaxillary teeth in two rows: outer row with 4*(15), 5(9), or 6(4) tricuspid teeth, central cusp longer; inner row with five teeth, gradually decreasing in sizefrom 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 2(12), 3(18), or 4*(1) tri- or pentacuspid teeth; central cusp broader than others. Dentary with 4*(31) large pentacuspid teeth, followed by six to nine small teeth, uni- to tetracuspid ( Fig. 2 ). Median cusp in all cuspidate teeth longer than remaining cusps; cusp tips slightly curved lingually in dentary, premaxillary teeth cusps approximately straight.

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

Dorsal-fin rays i,10*(31); first unbranched ray approximately one-half the length of second ray. Distal margin of dorsal fin nearly straight to somewhat convex. Dorsal-fin origin slightly behind middle of SL. Adipose-fin origin at vertical through second or third last anal-fin rays. Anal-fin rays iii*(27) or iv(4), 24(4), 25*(9), 26(11), 27(4), or 28(3). Anal-fin origin posterior to vertical through base of last dorsal-fin ray. Pectoral-fin rays i,11(1), 12*(16), or 13(14). Pectoral-fin tip not reaching pelvic-fin insertion. Pelvic-fin rays i,7*(31). Pelvic-fin origin slightly anterior to vertical through dorsal-fin origin. Caudal fin forked, lobes similar in size, i,17,i*(30) principal rays. Dorsal procurrent rays 11(1) or 12(1) and ventral procurrent rays 10(1) or 11(1).

Lateral line complete with 37*(24), 38(2), or 39(4) scales. Scale rows between dorsal-fin origin and lateral line 6(2), 7*(27), or 8(2); scale rows between lateral line and pelvic-fin origin 5*(28) or 6(3). Predorsal scales11 (12), 12*(8), or 13(6) arranged in regular series. Scale rows around caudal peduncle 14*(30). Scale sheath along anal-fin base 10-15 scales 14*(29), in single series, covering base of anteriormost rays. Axilar scale longer than wide, relatively folded in half, and extending over 1-2 longitudinal scale series.

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. Body with black midlateral stripe extending from second humeral spot to caudal-fin base. Caudal peduncle spot black expanded dorsally and ventrally, 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 two to three horizontal series of scales above lateral line; lower portion of spot narrow and slightly directed forward (one to two scales pigmented), extending over one to two horizontal series of scales below lateral line. Second humeral spot large, occasionally faint, not surpassing lateral line ventrally, extending over three horizontal series and two to three vertical series of scales, and in some specimens the lower portion wider than the upper portion. Scattered dark chromatophores on dorsal, adipose, caudal, and anal fins. Pectoral and pelvic fins with few dark chromatophores. Dark pigmentation on middle caudal-fin rays and along middle-distal portion of anal-fin rays ( Fig. 1 ).

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

Sexual dimorphism. Mature males of Astyanax bagual are recognized by the presence of small bony hooks on all fins. One paired bony hook per segment of ray in the last unbranched anal-fin ray and anteriormost anal-fin branched rays on middle and distal portions of rays. One paired bony hook per segment of ray on second to fifth pelvic-fin branched rays. Dorsal, pectoral, and caudal fins with few bony hooks dispersed in distal portions of rays. Gill glands (Burns & Weitzman, 1996) or fusion of anteriormost gill filaments of the ventral branch of first gill arch ( Terán et al., 2014) were not found macroscopically on the both mature males and females.

Distribution. Astyanax bagual is known from rio Taquari- Antas basin, rio Jacuí drainage, laguna dos Patos system, Rio Grande do Sul State, southern Brazil ( Fig. 3 ).

Etymology. The specific epithet bagual , from Tupi- Guarani, means wild horse, or what is mortal, or dangerous to mount. This expression is used mainly to convey the information that a given horse is a male reproductive in the countryside of Rio Grande do Sul State. The new species is named in allusion to the presence in mature males of bony hooks on all fins.

Ecological notes. Astyanax bagual was collected in relatively small, dark water rivers up to two meters deep, with stones and rocks on bottom, and moderate riparian vegetation. The collection localities are around 300 meters above sea level. An extensive examination of Astyanax material from fish collections and field expeditions, the species seems to be found only in rivers from mid-slope valleys and in the plateau sections of the Taquari-Antas basin ( Fig. 3 ).

Conservation status. Astyanax bagual is distributed in some of the main tributaries of the rio Taquari-Antas basin, but probably it is further widespread. Despite biological features of that species is unknown, considering the biology of its congeners, there is no imminent known threats to the species. Therefore, according to the International Union for Conservation of Nature (IUCN) categories and criteria ( IUCN Standards and Petitions Subcommittee, 2014), A. bagual can be classified as Least Concern (LC).

Figures

Fig. 1. Astyanax bagual, UFRGS 19525, 74.1 mm SL, male, holotype, rio Carreiro downstream to hydroeletric plant PCH Linha Emília, rio Taquari-Antas, laguna dos Patos system, Dois Lageados, Rio Grande do Sul State, Brazil.

Fig. 2. Astyanax bagual, UFRGS 17834, 68.4 mm SL, paratype. Upper and lower jaws left side, medial view. Scale bars = 1 mm.

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