Astyanax gymnodontus (Eigenmann, 1911) Pavanelli & Oliveira, 2009

Pavanelli, Carla Simone & Oliveira, Carlos Alexandre Miranda, 2009, A redescription of Astyanax gymnodontus (Eigenmann, 1911), new combination, a polymorphic characid fish from the rio Iguaçu basin, Brazil, Neotropical Ichthyology 7 (4), pp. 569-578 : 573-574

Astyanax gymnodontus (Eigenmann, 1911) , new combination

Figs. 4-5

Psalidodon gymnodontus Eigenmann, 1911: 166 (original description; type-locality: Porto União, rio Iguaçu ; illustration; holotype FMNH 54574 , ex CM 3204 ). - Eigenmann & Myers, 1929: 455 (reproduction of the original description; illustration). - Fowler, 1948: 162 (checklist of Brazilian freshwater fishes). - Géry, 1977: 578 (comparison with Henochilus wheatlandi ; referred to the Cheirodontinae; partial illustration). - Severi & Cordeiro, 1994: 41 (translation of the original description; rio Iguaçu; illustration). - Garavello et al., 1997: 74 (redescription; Segredo Reservoir). - Malabarba, 1998: 230 (type-species of Psalidodon). - Lima et al., 2003: 154 (checklist of South and Central American fishes).

Astyanax sp. F . -Sampaio, 1988: 70 (description; rio Iguaçu; illustration). -Severi & Cordeiro, 1994: 29 (description; rio Iguaçu; illustration). -Garavello et al., 1997: 73 (description; Segredo Reservoir). -Haluch & Abilhoa, 2005: 386 (comparison with Astyanax totae ). -Abilhoa & Duboc, 2007: 49 (comparison with Astyanax varzeae ).

Psalidodon sp. -Garavello et al., 1997: 74 (description; Segredo Reservoir).

Diagnosis. Astyanax gymnodontus can be distinguished from all other congeners at the rio Iguaçu basin except for A. varzeae by the combination of the following characters: thirdinfraorbital margin separated from preopercle by broad skin area as wide as 1/5 to 1/3 of its depth (vs. adjacent or separated by a narrower skin area); teeth with a cutting edge forming a straight line or a convex arc in frontal view (vs. concave arc); premaxillary teeth with five (rarely seven) cusps, with the median being the largest and the other cusps abruptly decreasing in size to the sides (vs. commonly seven, rarely four, five or nine cusps, gradually decreasing laterally); transversally located black humeral blotch (vs. longitudinally located); 21 to 24 anal-fin rays and 37 to 41 lateral-line scales (vs. 18 to 22 and 34 to 38, respectively, in A. totae ); and no hooks on pelvic or anal fins. Astyanax varzeae is the congener most similar to A. gymnodontus in the basin, but the latter can be diagnosed by having a deeper body, 2.4 to 3 times in the SL (vs. 3 or 3.5 in A. varzeae ), and a longer snout, 3.2 to 4.7 times in the HL (vs. 4.3 to 6.1).

Description. Body elongated and laterally compressed, body deeper at dorsal-fin origin. Predorsal and prepelvic regions of body rounded transversely. Dorsal profile of snout convex, straight or slightly concave from eye to supraoccipital process. Dorsal profile of body gently convex from supraoccipital process to dorsal-fin end, straight or slightly convex from this point to adipose-fin base, straight or slightly concave from this point to caudal fin. Ventral profile of body convex, between anterior tip of jaw and pelvic-fin origin, straight from this point to anal-fin origin. Dorsal-fin origin slightly forward or at vertical through pelvic-fin origin, its distal margin straight. Pectoral-fin origin at vertical through posterior edge of opercle, its margin rounded, when adpressed, reaching or almost reaching pelvic-fin origin. Pelvic-fin origin at about vertical through dorsal-fin origin, its margin slightly convex, when adpressed not reaching anal-fin origin. Anal-fin origin just behind vertical through end of dorsal-fin base, its distal margin slightly concave. Caudal fin with symmetric lobes, or inferior slightly longer, and scales only at base.

Dorsal-fin rays ii or iii,8 to 10 (mean = 9.4); pectoral-fin rays i,11 to 14 (mean = 12.5); pelvic-fin rays i,7 or 8 (mean = 7.5); anal-fin rays iii,19 to 22 (mean = 20.8). Lateral line complete, with 37 to 41 perforated scales, generally 39 or 40; 6 to 8 rows of scales above lateral line, generally 7, and 5 or 6 below.

Third-infraorbital margin separated from preopercle by a broad skin area, as wide as 1/5 to 1/3 of its depth. Dentary larger teeth 5 to 7, with three cusps, in anterior row, and smaller 4 to 7, generally 5 or 6 in posterior row. Premaxillary teeth 4 to 7, generally 5 or 6, with five cusps, in inner row, 1 to 4 with three cusps regular or irregularly arranged in outer row, when present. Outer row commonly not bilaterally symmetric. Maxillary teeth 1 to 4 with three cusps. All teeth with largest median cusp, abruptly decreasing in size up to smallest more laterally placed. Cutting edge of teeth with cusps in a straight line or forming a very wide convex arc in frontal view. Lips absent or, when present, ranging from poorly developed to completely covering premaxillary and dentary teeth. Polymorphism in teeth and lips development is shown in Fig. 5 .

Figures

Fig. 4. Astyanax gymnodontus, (a) “Astyanax sp. F” morphotype NUP 4122, 92.3 mm SL, Salto Santiago Reservoir; (b) “Psalidodon sp.” morphotype NUP 3707, 110.6 mm SL, Jordão Reservoir; and (c) “P. gymnodontus” morphotype NUP 4062, 91.0 mm SL, rio Jordão.

Fig. 5. Some examples of dental and lip polymorphisms displayed by Astyanax gymnodontus, with the number of the lot (all of NUP collection), SL in mm, and the number of premaxillary teeth in the outer row, on the left and right sides (in parentheses). Left column, well-developed lips: (a) 1583, 65.2 (0-0), (b) 4062, 97.1 (1-0), (c) 1653, 64.2 (1-1), (d) 618, 128.5 (1-3), (e) 3766, 97.5, (2-1), (f) 1643, 105.4(2-3), (g) 3686,92.2 (4-3), (h) 2719,99.9 (4-4); middle column, ill-developed lips:(i) 2297, 53.8 (0-1), (j) 1582, 93.2 (0-2), (k)1582, 85,2(0-3),(l) 4348,80.1 (1-1), (m)2050,66.2 (1-2), (n)1579, 72.0 (1-3),(o) 1643, 99.0(3-3), (p) 635,65.4 (3-4); right column,lacking lips:(q) 1583, 99.9(0-0), (r) 3766, 100.2(1-0),(s)1583, 98.0 (2-0), (t) 1579, 75.1(3-0), (u)3707, 68.0 (1-1), (v) 3037,97.4(2-2), (w)1583,80.4 (4-4).