Astyanax henseli

de Melo, Filipe A. G. & Buckup, Paulo A., 2006, Astyanax henseli, a new name for Tetragonopterus aeneus Hensel, 1870 from southern Brazil (Teleostei: Characiformes), Neotropical Ichthyology 4 (1), pp. 45-52 : 46-48

Astyanax henseli , nomen novum

Figs. 1–4

Tetragonopterus aeneus Hensel, 1870:87–88 (original description). Type locality: Porto Alegre.

Tetragonopterus rutilus Jenyns, 1842 in part – Steindachner, 1876 ( T. aeneus Hensel listed as junior synonym).

Astyanax fasciatus ( Cuvier, 1819) in part – Eigenmann, 1921 ( T. aeneus Hensel listed as junior synonym); Fowler, 1948 ( T. aeneus Hensel listed as junior synonym).

Astyanax aff. fasciatus ( Cuvier, 1819) in part – Malabarba, 1989 ( T. aeneus Hensel listed as junior synonym).

Astyanax obscurus ( Hensel, 1870) in part – Lima et al., 2003 ( T. aeneus Hensel listed as junior synonym).

Diagnosis. Astyanax henseli differs from other Astyanax species except A. saguazu Casciotta et al. and A. elachylepis Bertaco & Lucinda by the presence of a second vertically elongate humeral spot (vs. one elongate humeral spot). Astyanax henseli is distinguished from A. saguazu , A. elachylepis and members of the Astyanax fasciatus species complex by the autapomorphic presence of a space between the dentary teeth, which are relatively slender, with cusps positioned close to one another ( Figs. 1–2), and by the presence of a maximum of five cusps in each dentary tooth (vs. maximum of seven cusps). Astyanax henseli is also distinguished from A. fasciatus , A. rutilus , and A. elachylepis by the presence of two to five, usually five, tricuspid teeth, on the anterior margin of maxilla (vs. one to two teeth, usually one, on anterior margin of maxilla).

Description. Morphometric data are presented in Table 1. Body moderately elongate and compressed ( Figs. 3–4); deepest at dorsal-fin origin. Dorsal body profile convex from snout to dorsal-fin origin, straight along dorsal-fin base, slightly convex between insertion of last dorsal-fin ray and adipose fin. Ventral profile of head and abdomen convex; straight along anal-fin base. Dorsal and ventral profiles of caudal peduncle slightly concave.

Snout convex. First infraorbital expanded over small portion of maxilla. Two series of premaxillary teeth; teeth of outer series usually tricuspid, smaller than those of inner series, numbering four to five, usually five; teeth in inner series five with three to seven cusps. Two to five tricuspid teeth on anterior margin of maxilla, usually five teeth (mean=4.7, n=25). Dentary teeth slender, more so in young specimens; anterior four to five teeth larger than remaining teeth; larger teeth with three to five cusps; fifth tooth usually with three cusps; remaining teeth with one or two cusps. Space between dentary teeth, wider in young specimens.

Dorsal-fin rays ii,8–9 (mean=9.0, n=25); first unbranched ray about half the length of second unbranched ray. Dorsalfin origin located just anterior to middle of body. Adipose-fin origin located dorsal to posterior anal-fin ray insertion. Pectoral-fin rays i,11–13 (mean =12.6, n=25); tip of longest ray extending to or posterior to pelvic-fin origin in both males and females. Pelvic-fin rays i,7; pelvic-fin origin anterior to vertical line passing through dorsal-fin origin; longest pelvic ray reaching anal-fin origin in both sexes. Anal-fin rays iii– vi,22–27 (mean=24.3, n=25). Anal-fin origin posterior to vertical line through dorsal-fin origin.

Scales cycloid, moderately large. Lateral line complete with 37–41 scales (mean=38.4. n=22). Scale rows between dorsalfin origin and lateral line seven to eight (mean=7.1, n=25). Scale rows between lateral line and anal-fin origin six to seven (mean=6.4, n=25). Predorsal scales 11–16 (mean=13.1, n=24) regularly arranged. Scale sheath on anal-fin base consisting of one row with eight to 17 scales covering bases of unbranched rays and eight to 17 anterior branched rays. Scales around caudal peduncle 15–17 (mean=15.8, n=20).

Color in alcohol. Body pale brownish yellow. Lateral body stripe broad and dark posteriorly, becoming pale and narrow anterior to dorsal-fin origin. Lateral body stripe silvery in some specimens. Two dark humeral spots, slanted posteriorly and slightly wider dorsally; first spot vertically elongate, centered on third and fourth scales of scale row just dorsal to lateral line; second spot, very diffuse, located on first series of scales above lateral line, between seventh to tenth series of scales and extending over two or three horizontal series of scales. Middle caudal-fin rays darkly pigmented with pigmentation extending to tips of rays. Exposed borders of scales delineated by dark chromatophores. Dorsal and anal fins covered with scattered dark chromatophores, except for distinct unpigmented area at tip of dorsal fin and tip of anterior anal-fin lobe. Adipose fin mostly white. Head black to gray dorsally, especially dark near nape. Sides of head and opercles silvery.

Sexual dimorphism. When present, sexual bony hooks distributed over anal-fin and pelvic-fin rays. Pelvic fins with retrorse bony hooks on branched rays and posterior unbranched rays. Anal-fin rays of males with small retrorse bony hooks present from longest unbranched ray to last branched ray; hooks mostly present on posterior branches of rays; one pair of bony hooks per ray segment. Females without fin hooks (gonad examined in specimen MNRJ 14186, 60.8 mm SL).

Distribution. Known from the rio dos Sinos and rio Taquari drainages in Southern Brazil. Rio dos Sinos and rio Taquari are tributaries of the lago Guaíba which is located next to the city of Porto Alegre, and is the northernmost component of the laguna dos Patos system.

Etymology. The specific name henseli is in homage to R. Hensel for his contributions to Ichthyology in Southern Brazil.

Material e xamined: All specimens from Rio Grande do Sul, Brazil. Holotype: ZMB 7479 , (78.0 mm SL, male) Porto Alegre , R. Hensel. Non-types: MNRJ 14186 (15, 1 c&s, measured, 64.5– 28.9 mm SL), MNRJ 14297 (6, 20.5–27.7 mm SL), arroio do Carvalho, Vila do Carvalho , on road from Santo Antônio da Patrulha to Caraá, rio dos Sinos drainage, SantoAntônio da Patrulha , 29°45’S 50°25’W, 12 Jan 1995. MNRJ 14295 (6, 18.3–26.8 mm SL), rio dos Sinos, at Passo da Forquilha (?), near road crossing road from Caraá to Vila Rodolfo Tetour, Santo Antônio da Patrulha , 29°45’S 50°25’W, 12 Jan 1995. MNRJ 14296 (12, 14.8–34.2 mm SL), rio dos Sinos near bridge on road to Fundo Quente, upstream from rio dos Sinos, Santo Antônio da Patrulha , 29°45’S 50°25’W, 12 Jan 1995. MNRJ 22174 (2, measured, 91.4–108.4 mm SL), arroio do Meio, tributary of rio Taquari , Arroio Grande, 28 Nov 1999. MNRJ 22214 (1, measured, 70.2 mm SL) rio Forqueta , tributary of rio Taquari, in the extension area of the Salto Forqueta Hydroelectric dam, 29°4’37"S 52°12’59"W, 9 May 2001. MNRJ 22231 (6, measured, 73.2–89.3 mm SL), same locality of MNRJ 22214 , 10 May 2001. MCP 11223 (5 of 16, 58.6–85.0 mm SL), rio Cadeia on BR116 highway, between Nova Petrópolis and Dois Irmãos, 29°27´00"S 51°09´00"W, 30 Apr 1987. MCP 18396 (5 of 63, 44,8–68,0 mm SL), rio dos Sinos at João Fernandes beach near Caraá, 29°46´27"S 50°26´08"W, 14 Dec 1995. MCP 19439 (5 of 13, 28,0–89,7 mm SL), arroio Carvalho at Caraá, 29°48´04"S 50°28´25"W, 14 Jan 1996.