Astyanax dissensus Lucena &Thofehrn, 2013

de Lucena, Carlos A. S., Castro, Jonas Blanco & Bertaco, Vinicius A., 2013, Three new species of Astyanax from drainages of southern Brazil (Characiformes: Characidae), Neotropical Ichthyology 11 (3), pp. 537-552 : 538-541

Astyanax dissensus Lucena &Thofehrn , new species Figs. 1-2

Astyanax sp. 2 . - Becker et al., 2013: 82 (listed).

Holotype. MCP 47000 , 65.1 mm SL, Brazil, Rio Grande do Sul, Candiota, arroio Candiota, downstream of Thermoelectric Power Plant , rio Jaguarão drainage, 31º34’36”S 53º40’22”W, 16 Feb 2001, R. E. Reis, C. M. Joenck & T. Borges.

Paratypes. Brazil, Rio Grande do Sul State, laguna dos Patos system. MCN 19585, 2, 58.9-66.1 mm SL, MCP 17361 , 31 (28, 47.6-75.7 mm SL, 1 c&s 53.1 mm SL), UFRGS 17097 , 2 , 40.2- 66.2 mm SL, arroio Taquara, road of Boa Vista ca. 5 km of road BR-290, Minas do Leão , ca. 30º09’S 52º02’W, 24 Nov 1993, J. F. P. da Silva & W. Bruschi. MCP 34788 , 3 (2, 52.1-65,1 mm SL), tributary of rio Basílio , ca. 25 km to NW of Herval, 31º52’12”S 53º30’40”W, 16 Nov 2003, R. E. Reis, P. Lehmann, M. Abreu & C. Alho. MCP 47404 , 2 , 40.4-44.8 mm SL, arroio Paraíso , locality of Rincão da Porta , Cachoeira do Sul , ca. 29º41’S 53º09’W, 15 Sep 1993, C. A. S. Lucena, J. F. P. da Silva & V. A. Bertaco. MCP 47407 , 1 , 56.1 mm SL, arroio Hilário on the road Caçapava do Sul - Lavras do Sul , Lavras do Sul , 30º46’03”S 53º48’23”W, 26 Apr 2000, C. A. S. Lucena, J. F. P. da Silva & V. A. Bertaco. MCP 47409 , 1 , 60.3 mm SL, arroio Reduzindo on the road Pedro Osório - Basílio , rio Piratini drainage, 31º54’32”S 52º35’59”W, 20 Nov 1999, C. A. S. Lucena, Z. M. S. Lucena, E. H. L. Pereira & V. A. Bertaco. MCP 43236 , 6 , 43.1-62.9 mm SL, stream tributary of rio Jaguarão , 31 o 53’07”S 56º36’04”W, Pedras Altas , 4 Feb 2006, E. Krause Lanés. MCP 40758 , 4 , 51.4-64.6 mm SL, tributary of arroio das Lavras, rio Camaquã drainage, Lavras do Sul , 30º50’02”S 53º53’52”W, 31 Jul 2007, T. P. Carvalho, A. R. Cardoso & J. M. Wingert. MCP 38352 , 1 , 59.4 mm SL, arroio Lageado tributary of arroio Arambaré , Pedro Osório , 31º51’51”S 52º49’24”W, 22 May 2005, R. E. Reis, P. C. Lehmann & E. H. L. Pereira. MCP 47412 , 1 , 63.5 mm SL, arroio da Gringa, ca. 12 km N from Dona Francisca dam, Agudo , 29º23’16”S 53º13’26”W, 23 Aug 1998, R. E. Reis, J. F. P. da Silva & V. A. Bertaco. Rio Tramandaí system. MCP 21119 , 1 , 84.2 mm SL, lagoa Fortaleza, Cidreira, 30º09’02”S 50º14’39”W, 20 Jul 1998, V. A. Bertaco & D. Gerlain. Rio Uruguay drainage. MCP 9493 , 18 (8, 43.8-58.0 mm SL, 1 c&s 55.2 mm SL), stream on the road Cacequi-São Francisco de Assis, Vila Itapevi, 29º53’00”S 54º49’00”W, 14 Sep 1983, C. A. S. Lucena, L. R. Malabarba & R. E. Reis. MCP 47410 , 1 , 69.6 mm SL, arroio Canoin on the road Pirapó-São Nicolau, ca. 28º08’S 55º14’W, 2 Nov 1998, C. A. S. Lucena, A. Bergmann, E. H. L. Pereira. MCP 12368 , 1 , 71.8 mm SL, rio Canoas , on the road Anita Garibaldi- Abdon Batista, ca. 27º39’S 51º05’W, 8 Sep 1988, E. H. L. Pereira, M. Vargas, A. Bergmann & P. Azevedo. MCP 13117 , 2 , 67.0- 70.0 mm SL, rio Canoas , on the road BR-282, Vargem - São José do Cerrito , ca. 27º33’S 50º53’W, 31 Mar 1989, L. A. Bergmann, P. Azevedo and M. Vargas. MCP 18558 , 3 , 64.5-66.6 mm SL, rio Dourado between Três Barras and Mariano Moro, 27º22’S 52º14’W, 21 Sep 1995, E. Filho, V. Schulz, P. Iaczinski & S. Meurer. MCP 47402 , 13 , 55.9-74.3 mm SL, arroio Capivari, on the road BR-453, rio Jaguari drainage, 29º 21’10”S 54º 28’32”W, 11 May 2001, C. A. S. Lucena, J. F. P. da Silva, E. H. L. Pereira & V. A. Bertaco. MCP 47403 , 1 , 77.0 mm SL, rio Uruguay near mouth of the rio Ligeiro , Marcelino Ramos, 27º31’28”S 51º50’15”W, 14 Nov 1996, E. H. L. Pereira, J. F. P. da Silva & R. E. Reis. MCP 27605 , 4 (3, 43.3-48.0 mm SL), arroio Caraí- Passo, on the road São Francisco de Assis - Manuel Viana, rio Ibicuí drainage, 29º31’03”S 55º10’49”W, 12 May 2001, C. A. S. Lucena, V. A. Bertaco, E. H. L. Pereira & J. F. P. da Silva. MCP 47406 , 1 , 51.4 mm SL, tributary of the rio Quaraí , on the road Quaraí to Estação Férrea Baltazar Brum , ca. 2 km N from Quaraí, 30º21’52”S 56º23’26”W, 25 Apr 2004, R. E. Reis, A. Bergmann & P. Azevedo. MCP 47405 , 3 , 42.0-47.2- mm SL, river on the road Quaraí to Estação Férrea Baltazar Brum , ca. 20 km NE from Quaraí, 30º14’38”S 56º18’23”W, 24 Apr 2004, R. E. Reis, A. R. Cardoso, F. R. V. Ribeiro & M. Abreu. MCP 47408 , 1 , 43.4 mm SL, rio Garupá on the road Uruguaiana-Quaraí, border Uruguaiana-Quaraí, 30º07’24”S 56º25’29”W, 22 Jul 1986, R. E. Reis, A. R. Cardoso, F. R. V. Ribeiro & M. Abreu. MCP 47518 , 2 , 41.7 -46.0 mm SL, 1 c&s, 42.6 mm SL, rio Quaraí-Mirim on the road Uruguaiana / Quaraí, Quaraí, 30º15’29”S 56º30’37”W, 30 Sep 1996, J. F. P. da Silva, W. Santos, E. S. Vidal & V. A. Bertaco .

Diagnosis. Astyanax dissensus differs from all congeners inhabiting the rio Uruguay basin, laguna dos Patos and rio Tramandaí systems, except A. ojiara , in having one heptacuspid tooth on maxillary (vs. tri- to pentacuspid teeth). From A. ojiara it differs by the head length (22.7- 27.3% vs. 27.3-29.5% of SL) and by the presence of hooks on anal fin on males (vs. all fins with hooks). The following combination of characters distinguish A. dissensus from all others species of the genus (including species complex A. bimaculatus and A. scabripinnis ): the presence of two humeral spots, the first spot vertically elongate, a conspicuous caudal spot, 35-39 perforated lateral line scales, 6-7 scale rows between dorsal-fin origin and lateral line, 22-28 branched anal-fin rays, predorsal region scaled, one heptacuspid maxillary tooth, body depth (37.2-44.2% of SL), and head length (22.7-27.3% of SL).

Description. Morphometric data summarized in Table 1. Body compressed and deep, with greatest body depth anterior to dorsal-fin origin. Dorsal profile of head straight or slightly concave from region above the eye to supraoccipital spine. Dorsal body profile convex from tip of supraocciptal spine to base of last dorsal-fin ray; straight from latter point 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 to slightly concave in the 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. Maxilla extending to vertical through anterior margin of orbit. Maxilla slightly widened anteroposteriorly.

Two tooth rows in premaxilla; outer row with 2(2), 3(57)*, 4(14), or 5(2) pentacuspid teeth, central cusp longer; inner row with five teeth, gradually decreasing in length from the first to fifth with seven to nine cusps, except the first teeth with asymmetric five cups; central cusp twice as long and broad as others cusps. Maxilla with one tooth bearing seven cusps (in some specimens one of two lateral cusp may be worn. In this case, taking six cusps); central cusp slightly broader than others. Dentary with nine to ten teeth. Five or six anteriormost dentary teeth decreasing gradually, first four or five hexacuspid, fifth or sixth tetracuspid teeth; remaining three or four, smaller, uni- to tricuspid ( Fig. 2 ).

Dorsal-fin rays ii,8(5), or 9(73)*; first unbranched ray approximately half length of second ray. Distal margin of dorsal-fin nearly straight to somewhat convex. Dorsal-fin origin approximately at middle of SL. Origin of the adipose fin at vertical through fifth or sixth last rays of the anal-fin. Anal-fin rays v (2 c&s), 22(6), 23(20), 24(18), 25(21)*, 26(4), 27(7), or 28(2). First unbranched ray normally only apparent in c&s specimens. Anal-fin profile smoothly concave. Anal-fin origin posterior to vertical through base of last dorsal-fin ray. Pectoral-fin rays i,11*(25), 12(21), or 13(3). Pectoral-fin tip not reaching pelvic-fin insertion; reaching the pelvic-fin origin in small specimens (ca. 41.0 mm SL). Pelvic-fin rays i,6(4), or 7(75)*. Pelvic-fin origin slightly anterior to vertical through dorsal-fin origin. Pelvic-fin tip extend beyond the genital opening but not reach the anal-fin origin. Caudal fin forked, lobes similar in size, rounded, i,17,i principal rays. Dorsal procurrent rays 11(1) and ventral procurrent rays 8(1).

Lateral line complete with 35(2), 36(22), 37(40)*, 38(8), or 39(4) scales. Scale rows between dorsal-fin origin and lateral line 6(62)*, or 7(17); scale rows between lateral line and pelvic- ( Burns & Weitzman, 1996) were not found on first gill arch in either males or females.

Distribution. Astyanax dissensus is known from the laguna dos Patos system and rio Uruguay drainage ( Fig. 3 ). One specimen was captured from coastal lagoon of rio Tramandaí system (MCP 21119). Astyanax dissensus appears to be rare in the rio Tramandaí system because although the sampling efforts in the region it is not mentioned in the Malabarba et al. (2013).

Etymology. The specific epithet dissensus from Latin, disagreement, in reference to the larger maxillary heptacuspid tooth peculiar to the species and unusual in Astyanax species. fin origin 4(1), 5(62), or 6(16). Predorsal scales 9(5), 10(33), 11(27)*, 12 (4), or 13(2) arranged in regular series. Scale rows around caudal peduncle 14(77)*. Scale sheath along anal-fin base 8*-15 scales, in single series, covering base of anteriormost rays.

Precaudal vertebrae 15(2) or 16(1); caudal vertebrae 20(3); total vertebrae 35(2) or 36(1). Supraneurals 5(3). Gill-rakers upper branch 6 (40)*, 7(35), or 8(3); lower branch 10(7), 11(37), 12(28)*, or 13(6); total number 16(2), 17(31), 18(19)*, 19(18), 20(4), or 21(2).

Figures

Fig. 1. Astyanax dissensus, new species, MCP 47000, 65.1 mm SL, holotype, arroio Candiota, rio Jaguarão drainage, Candiota, Rio Grande do Sul, Brazil.

Fig. 2. Astyanax dissensus, new species, MCP 19561, 42.6 mm SL, paratype, upper and lower jaws teeth, left side, lateral view.Scale bar = 1 mm.

Fig. 3. Map of southern Brazil and Uruguay, showing the distribution of the material examined of Astyanax dissensus. Some symbols represent more than on lot or locality. Black circle = type locality.