Astyanax goyacensis Eigenmann, 1908

Garutti, Valdener & Langeani, Francisco, 2009, Redescription of Astyanax goyacensis Eigenmann, 1908 (Ostariophysi: Characiformes: Characidae), Neotropical Ichthyology 7 (3), pp. 371-376 : 372-375

Astyanax goyacensis Eigenmann, 1908 Figs. 1-2

Astyanax goyacensis Eigenmann, 1908: 96 (description; typelocality: Goiaz [= Brazil, Goiás State, rioAraguaia drainage, upper course of rio Vermelho at the municipality of Goiás]); - Eigenmann, 1921: 231 (identification key), 260 (copy of Eigenmann, 1908); - Géry, 1977: 430 (identification key); - Garutti, 1998: 116 (list of comparative material); - Garutti, 1999: 590 (list of comparative material); -Bertaco & Garutti, 2007: 29 (list of comparative material).

Astyanax goyazencis (error); Eigenmann, 1910: 433 (catalog).

Material examined. Holotype. MCZ 89558, 76.0 mm SL, Goyaz , Thayer Brazilian Expedition. Topotypes. Brazil, Goiás State:

MZUSP 4905 , 5 , 57.2-75.7 mm SL, rio Vermelho, city of Goiás (approx. 15º55’S 50º07’W), rio Araguaia basin, 14 Sep 1966 ; DZSJRP 10857, 20 (2 cs), 56.4-85.4 mm SL, rio Vermelho, about 3 km above the city of Goiás (15º55’11”S 50º07’51”W), rio Araguaia basin, 1 Nov 2005 .

Diagnosis. Astyanax goyacensis differs from all other congeners, except those belonging to the A. bimaculatus species complex (sensu Garutti, 1998), by presenting a conspicuous black humeral horizontally ovate spot, and two superficial and diffuse brown bars in the humeral area. It is distinguished from A. asuncionensis Géry, 1972 and Astyanax sp., two syntopic species from the sub-group of the Astyanax bimaculatus species complex without a black lateral stripe, by the reticulate chromatophore pattern (vs. striped in A. asuncionensis ), the black lateral stripe (vs. absent in A. asuncionensis and Astyanax sp.), and the smaller orbital diameter, 25.5-29.8 (vs. 33.1-39.5% HL in Astyanax sp.). From species of the bimaculatus sub-group with a black lateral stripe, it differs from A. argyrimarginatus and A. unitaeniatus by the fewer lateral line perforated scales, 35-40 (vs.> 41). From A. clavitaeniatus , A. novae , and A. saltor , by the smaller eye diameter, 25.5-29.8 (vs.> 31.6% HL). From A. utiariti by the smaller eye diameter 25.5-29.8 (vs. 28.5-34.3% HL), larger interorbital width, 37.4-48.0 (vs. 32.7-38.4% HL), and fewer premaxillary inner row tooth cusps, four or five (vs. five to seven). Astyanax goyacensis differs from A. incaicus and A. rupununi by the black lateral stripe shape, continually narrowing forward (vs. abruptly narrowed forward, in a clubshaped form) (specimens in alcohol), and deeper caudalpeduncle, 11.5-14.5 (vs. 10.5-11.3% SL and 9.1-9.2% SL, respectively). From A. siapae it differs by the fewer anal-fin rays, 21-28 (vs. 28-33), smaller eye diameter, 25.5-29.8 (vs. 31.4- 44.2% HL), and by the black lateral stripe shape, continually narrowing forward (vs. abruptly narrowed forward, in a clubshaped form).

Description. Morphometric and meristic data presented in Table 1. Body compressed, moderately elongated. Largest body depth generally two to three scales ahead of dorsal-fin origin. Predorsal and preventral areas transversely rounded. Dorsal and ventral body portions, defined by imaginary horizontal line passing through buccal opening, unequal, dorsal shallower. Dorsal and ventral profiles asymmetric. Dorsal profile smoothly convex from snout tip to dorsal-fin origin, straight from dorsal fin to caudal-fin base, slightly concave at limits of adipose fin. Ventral profile evenly convex between snout tip and pelvic fin, straight from pelvic to anal fin, straight from anal-fin base to caudal fin. Dorsal fin origin behind first body half, its distal border straight or smoothly convex; when adpressed to body, reaching 4 th- 5 th (males) or 8 th- 9 th (females) scales anterior to adipose fin. Adipose-fin origin at vertical through last 4 th- 5 th branched anal-fin rays; when adpressed to body, never surpassing vertical through tip of last anal-fin ray. Pelvic-fin origin ahead of dorsal-fin origin and middle of body; its distal border smoothly convex or straight, never reaching anal-fin origin when adpressed to body. Anal fin origin distinctly behind dorsal-fin base, its distal border straight or smoothly concave along first third.

Pectoral fin rays i,11(5), i,12*(9) or i,13(9); pelvic fin rays i,7*(23); caudal fin i,14,i(1), i,15,i(1), or i,17,i(21); dorsal fin rays ii,8(3) or ii,9*(20); anal fin rays iii,18(1), iii,21(4), iii,22*(3), iii,23(1), iv,20(1), iv,21(8), iv,22(5), iv,23(1), iv,24(1), or v,21(1). Males with retrorse bony hooks on last unbranched and 10 first branched anal-fin rays, and along first to sixth branched pelvic-fin rays.

Head small, higher than long, moderately wide, and eye small. Mouth terminal, horizontal. Lower and upper jaws equal in length. Snout not very pointed, smaller than eye diameter. Maxillary not surpassing second infraorbital posterior margin, with almost same size of snout or smaller.

Dentary with 4 large teeth, followed by 6-8 small; large ones, tetra*, penta*, hexa, and heptacuspid; smaller teeth uni or tricuspid*. Premaxilla with two tooth-rows: inner row with 5 teeth, tetra* and pentacuspid*; outer row 3-3(1), 3-4(2), 4- 3(1), 4-4*(13), 4-5(1), and 5-5(1) tricuspid teeth. Maxilla with 0-0(2), 1-0(1), 0-1(1), and 1-1*(18) small uni or tricuspid* teeth. Central cusp always larger than remaining cusps.

goyacensis Eigenmann , holotype (MCZ 89558) and topotypes

(N: number of specimens; M: mean; SD: standard deviation).

Lateral line complete, with 35(1), 36(2), 37(8), 38*(6), 39(4), or 40(1) perforated scales. Scale rows between dorsal-fin origin and pelvic-fin origin 11(1), 12(3), 13*(11), 14(10), or 15(1), of which 5(1), 6(4), 7*(19), or 8(2) above, and 4(1), 5*(12), or 6(13) below lateral line. One or two scale-rows covering anal-fin base.

Gill rakers 8-9+1+11-12(2); supraneurals 4(1) or 5(1); vertebrae 36(2); procurrent rays 11(1) and 13(1) dorsal, and 9(1) and 11(1) ventral.

Color in life. Body most silvery ( Fig. 1 ). Head dark brown dorsally and silver laterally. Body dorsal line dark brown; flank chestnut light along four to seven scale rows above lateral line, and with reticulate chromatophore pattern (borders of scales), conspicuous and forming zigzag lines (between scale rows); flank below lateral line silvery. Gular and body ventral areas whitish. Humeral area with conspicuous black horizontal oval spot and two diffuse vertical bars. Caudal peduncle most silvery ventrally and chestnut dorsally. Dorsal fin grayish. Adipose fin slightly yellowish. Pectoral fin yellowish white. Pelvic fin whitish in proximal half and yellow to slightly orange in posterior one. Anal fin yellow-orange in first third, something blackened posteriorly. Caudal-fin medium rays black, intermediary rays yellowish, outer rays reddish. Iris with ferrugineous dorsal spot.

Color in alcohol. Body general coloration light brown with chromatophores concentrated on scale borders, forming reticulated pattern on flank, sometimes also with inconspicuous brown longitudinal lines between scale longitudinal series ( Fig. 2 ). Head brown dorsally, light brown laterally, and silvery at opercular area. Body brown dorsally, light brown laterally, and cream ventrally. Gular area cream. Conspicuous black, horizontally oval humeral spot formed by densely grouped black chromatophores, extending horizontally from 2 nd to 6 th or 3 rd to 7 th scales on first series above lateral line, and vertically along one and half scale series above lateral line, limited by silvery areas anterior and posteriorly. Two irregular brown vertical bars on humeral region, first through humeral oval spot and second 2-3 scales behind; first bar usually six or seven scales high, and three scales wide; second bar usually five scales high, and three scales wide. Black midlateral stripe from second vertical bar to middle caudal-fin rays extremity, continually narrowing forward and backward, being less than one scale high at extremities, and two scales high at caudal peduncle. Dorsal fin membrane with numerous small dark chromatophores.Adipose fin with small, numerous and dispersed dark brown chromatophores. Pectoral fin with scattered small dark chromatophores on rays and membrane. Pelvic fin rays with scattered small dark chromatophores.Anal fin membrane with numerous small dark chromatophores. See also “Comments on the color pattern in A. bimaculatus species complex” below.

Sexual dimorphism. Mature males with sexual retrorse bony hooks on the anal-fin and pelvic-fin rays. Hooks occur on the last unbranched and up to 10 first branched anal-fin rays, and along the first to sixth branched pelvic-fin rays. Specimens captured in September, winter dry season, never presented any kind of secondary sexual dimorphism, although only five specimens have been captured and were externally examined. On the other hand, in November, at the beginning of the wet season and higher temperatures, the males presented conspicuous hooks on the anal and pelvic fins, and also fully developed gonads. Males are also shallower and smaller than females.

Habitat. The rio Vermelho at the site where A. goyacensis was captured is four meters wide and at most one meter deep. The waters were slow-flowing and turbid on November (beginning of the rainy season), and the substratum is composed of pebbles of varied sizes, coarse and fine sand, with silt and clay in smaller proportion. Relatively intact riparian forest covers the river banks. Astyanax goyacensis occurs syntopically with at least two other species of the A. bimaculatus species complex, A. asuncionensis and an undescribed species, which seemingly constitutes mixed schools with A. goyacensis once both were captured at the same time and in the same fishing trap.

Geographical distribution. So far known from the sub-basin of the rio Vermelho, rio Araguaia basin.

Comments on the color pattern in Astyanax bimaculatus species complex. Chromatophores in the species of the Astyanax bimaculatus complex (and probably in many other species of this genus) are distributed in at least two different levels of the integument. In the first one, more superficial, epidermic and clearly disposed above scales, chromatopores compose reticulated, striped, and dispersed patterns as showed by A. argyrimarginatus , A. goyacensis , and A.

unitaeniatus (reticulated), A. abramis (Jenyns, 1842) , A. asuncionensis , and A. maculisquamis Garutti & Britski, 1997 (striped), and A. altiparanae Garutti & Britski, 2000 and A. lacustris (Lütken, 1875) (dispersed). In the second level, deeper and dermic, also visible after scales removal, chromatophores compose more conspicuous and darker chromatic features such as the humeral oval spot, present in all species of the complex, the two lateral and vertical bars, commonly present also in the humeral region (the first through oval spot and the second slightly behind), and the caudalpeduncle spot or the lateral body stripe, which were used by Garutti (1999) to circumscribe respectively the “black lateral stripe” and the “caudal-peduncle spot” sub-groups in the A. bimaculatus species complex. The interaction among these two levels of chromatophores disposition may sometimes maximize the color features, such as the two vertical humeral bars of A. goyacensis , which are composed by chromatophores located in the epidermis and dermis.

The lateral stripe present in Astyanax argyrimarginatus , A. clavitaeniatus , A. goyacensis , A. incaicus , A. novae , A. rupununi , A. saltor , A. siapae , A. unitaeniatus , and A. utiariti can extend above lateral line from humeral spot, or a little behind, to the caudal peduncle and along middle caudal-fin rays; usually the lateral stripe is conspicuously deeper at the caudal peduncle in the same region of the caudal-peduncle spot. The caudal-peduncle spot, as in A. abramis , A. asuncionensis , A. altiparane , A. bimaculatus (Linnaeus, 1758) , A. lacustris , and A. maculisquamis , usually extends along 8-10 last scales in the first row above lateral line. Furthermore, some species of the A. bimaculatus complex can also present a silvery lateral stripe, which can cover the dark lateral stripe completely, as in A. abramis (which presents a very faint dark lateral stripe, if any), or surround it dorsally and ventrally, but never the caudal-peduncle spot, as in A. argyrymarginatus .

Figures

Fig. 1. Astyanax goyacensis Eigenmann, DZSJRP 10857, topotype, 75.2 mm SL, rio Vermelho, Municipality of Goiás, Goiás State, rio Araguaia basin (upon capture).

Fig. 2. Astyanax goyacensis Eigenmann, DZSJRP 10857, topotype, 57.1 mm SL, rio Vermelho, Municipality of Goiás, Goiás State, rio Araguaia basin (alcohol preserved specimen).