Cyanocharax alegretensis Malabarba & Weitzman, new species

(Figs. 4, 7, 9, 15, 39-44, Table 6)

Diagnosis. The convexity of both the distal margin of the anal fin and of the body profile along the anal-fin base in mature males distinguish C. alegretensis from C. lepiclastus, which has both the distal margin of the anal fin and of the body profile along anal-fin base nearly straight, and from C. dicropotamicus, C. itaimbe, C. alburnus, and C. tipiaia, that have the distal margin of the anal fin concave, and body profile along anal-fin base nearly straight. A distal margin of the anal fin nearly straight in mature females also distinguishes C. alegretensis from C. lepiclastus, C. dicropotamicus, C. itaimbe, C. alburnus, and C. tipiaia (in which the distal margin of the anal fin is concave in mature females. The number of branched anal-fin rays (23 -30, usually 25-27) distinguishes C. alegretensis from C. macropinna (28-35, usually 29-33 branched anal-fin rays).

Description. Morphometric data given in Table 6. Body moderately elongated and compressed. Dorsal head profile nearly straight, with pronounced concavity at nape in large specimens. Dorsal body profile from nape to dorsal-fin origin convex, and nearly concave between dorsal-fin origin and adipose fin. Ventral body profile from lower jaw to pelvic-fin origin deeply convex, and slightly concave from pelvic- to anal-fin origins. Ventral body profile along anal-fin base nearly straight in young and females to deeply convex in mature males. Dorsal and ventral profiles of the caudal peduncle nearly straight to slightly concave.

Head small (21.5-24.0% of SL). Eyes relatively large (39.3-46.9% of HL). Maxilla large positioned at an angle of 45 degrees relative to long body axis. Posterior tip of maxilla usually reaching or crossing a vertical line that extends through anterior border of pupil.

Two series of premaxillary teeth. Teeth of outer series usually tricuspid, smaller than those of inner series, numbering 3 to 4, most rarely 2 or 5. Four teeth with 5 cusps in inner series, most rarely with 3 cusps. Four to six maxillary teeth usually ranging from 5 cusps to conical. Three large dentary teeth with 5 cusps, followed by a medium size tooth usually with 3 cusps and a series of 6 to 10 much smaller ones, conical or ranging from 3 cusps to conical, from anteriormost to posteriormost teeth. Second dentary tooth inserted at a lower position in jaws, in such a way that tip of its longest cusp reaches only as high as tip of second largest cusp of first and third dentary teeth (Fig. 44).

Dorsal-fin rays ii,8 (n = 36) (Fig. 9). Dorsal-fin origin near middle of body length. Adipose fin dorsal to posterior anal-fin ray insertion.

Anal-fin rays iii-vi, 23-30 (x̄ = 26.6, n = 185). Anal-fin origin nearly ventral to dorsal-fin origin at middle of body length. Anal-fin distal border nearly straight in females, and deeply convex in mature males. Anal-fin rays of males with very small retrorse bony hooks, present in largest unbranched ray and anterior 6 to 9 branched rays (Fig. 7). Additional tiny hooks arc sometimes present in some of remaining branched rays, until 16th. Hooks usually present on posterior branches and posterior border of lepidotrichia. Usually one pair of hooks per bony ray segment.

Pectoral-fin rays i, 9- 11 (x̄= 9.8, n = 36). Tip of longest rays extend posterior to pelvic-fin insertion in both males and females. Pelvic-fin rays i, 6 (x̄= 6.0, n = 36, one specimen with i, 5). Pelvic-fin origin anterior to dorsal-fin origin. In females distal end of longest rays may or may not reach anal-fin origin. In mature males distal end of longest rays always reach anal-fin origin. Pelvic fins with ventromedial, usually unpaired retrorse bony hooks on first unbranched and all branched rays in sexually mature males (Fig. 4). Principal caudal rays 10/9.

Scales cycloid. Lateral line incomplete, with 5 - 12 (x̄= 9.0, n = 36) perforated scales (one of 35 specimens counted with alternating scries of perforated and non-perforated scales: 9/22/3/4). Total number of scales in the lateral line series 36- 38 (x̄= 36.8, n = 23). Scale rows between lateral line and dorsal-fin origin, 5-6 (x̄ = 5.9, n = 35). Scale rows between lateral line and pelvic-fin origin, 4 -5 (x̄= 4.4, n = 35). Predorsal scales, 11 - 15 (x̄ = 12.7, n = 26), usually in an irregular series. Males and females with a sheath of scales on anal-fin base, consisting of one row with 12- 18 small scales, covering bases of unbranched rays and first 12 to 18 branched rays. Vertebrae 35-37 (x̄= 36.1, n = 20), including Weberian apparatus and posterior half centrum (counts taken from x-ray negatives from MCP 11232).

Color in alcohol. Figs. 39-41. Body pale brownish yellow in specimens preserved in formalin long enough to destroy guanine pigment. Midlateral body stripe broad and diffuse. Dark humeral spot small and not clearly delimited from midlateral body stripe. Exposed borders of scales of dorsal portion of body delineated by dark chromatophores. Caudal fin without obvious marks, except for somewhat dark pigmentation that extends along entire length of middle caudal-fin rays in some specimens. Dorsal fin darkly pigmented except for distinct unpigmented area at its tip. Anal fin somewhat dusky, more intensely along distal border. Adipose fin slightly pigmented. Head black to gray dorsally, especially dark at nape. Sides ofhead whitish yellow.

Color in life. Described from photos taken just after formalin fixation (Figs. 42 and 43). Body light pale brownish yellow. Sides of head and belly silvery white. Lateral stripe on body broad and blue to grayish, from head to caudal-fin base. Humeral spot present. Caudal, dorsal, and anal fins light reddish, except for distinct unpigmented area at tip of dorsal fin. Narrow distal border of anal fin of males intensely pigmented.

Sexual dimorphism. Males of C. alegretensis have a convex distal border of anal-fin, contrary to the nearly straight profile of the fin margin in females. Males are also recognized by the presence of anal and pelvic-fin hooks, and longer pelvic and dorsal-fin (Table 6).

Etymology. Alegrete is a traditional county near the type locality of C. alegretensis.

Ecological notes. Field notes from MCP 11232 and MCP 11498 register clear water, with a medium speed current and bottom covered with rocks, stones and sand.

Distribution. This species is known only from the rio Ibicuí tributaries in Rio Grande do Sul state, Brazil (Fig. 1).

Holotype. MCP 25974, creek on road Santana do Livramento-Alegrete, Alegrete, Rio Grande do Sul, Brazil; 13 Nov 1986; C. A. Lucena, L. A. Bergman & P. V. Azevedo.

Paratypes. Rio Grande do Sul, Brazil: MCP 15199 (16, 27.8-37.9 mm SL), rio Jaguarizinho, Florida, Santiago; 8 Jan 1978. MCP 11498 (24, 27.2-43.0 mm SL), tributary of rio Ibirapuitã, Sao Leandro, Rosario do Sul; 13 Nov 1986. MCP 11232 (83: 10 c&s, 25.9-43.1 mm SL), MZUSP 82260 (25), MNRJ 23843 (25, 27.2-39.7 mm SL), USNM 357245 (25), tributary of rio Ibirapuitã, Sao Leandro, Rosario do Sul; 13 Nov 1986. MCP 11473 (34, 23.7-38.3 mm SL), collected with holotype.

Non-type specimens. Rio Grande do Sul, Brazil: MCP 26784 (208), arroio Ibicuí da Faxina, BR 158, Santana do Livramento.