Astyanax xavante, Garutti & Venere, 2009

Garutti, Valdener & Venere, Paulo Cesar, 2009, Astyanax xavante, a new species of characid from middle rio Araguaia in the Cerrado region, Central Brazil (Characiformes: Characidae), Neotropical Ichthyology 7 (3), pp. 377-383 : 378-381

Astyanax xavante , new species

Fig. 1

Astyanax scabripinnis (not Jenyns, 1842), Souza & Moreira- Filho, 1995 ( Brazil, Mato Grosso, Barra do Garças; genetic features).

Holotype. MZUSP 100375 , 57.3 mm SL, Brazil, Mato Grosso, Barra do Garças, creek tributary to the córrego Avoadeira, inside the Parque Estadual da Serra Azul , approx. 15 o 53’S 52 o 15’W, 1 Feb 2005, V. Garutti & P. C. Venere.

Paratypes. MCP 43325, 45 , 22.6-58.2 mm SL and MZUSP 100376, 102 (3 cs), 18.8-59.6 mm SL, same data as for the holotype .

Non-type specimens. All from Brazil, Mato Grosso, Barra do Garças, córrego Avoadeira, approx. 15 o 53’S 52 o 15’W. DZSJRP 11287, 67, 26.6-56.6 mm SL, 5 Apr 2005, V. Garutti et al .; ICLMA 503 , 52 , 25.0- 57.2 mm SL , 1 Feb 2005, V. Garutti et al .

Diagnosis. From the species assigned to the Araguaia- Tocantins basin, Astyanax xavante differs readily by having humeral spot vertically elongated vs. horizontally oval in A. argyrimarginatus , A. asuncionensis , A. goyacensis , A. kullanderi , A. novae , A. unitaeniatus , and other undescribed forms of the Astyanax bimaculatus species complex; fewer lateral-line scales, 34-37 vs. more than 48 in A. elachylepis and A. symmetricus ; larger body depth, 35.5-40.2 vs. 25.0-28.6% of SL in A. gracilior ; more anal-fin rays, 23-26 vs. 18-19 in A. scintillans ; and fewer maxillary teeth, 1-3 vs. 4-7 in A. guianensis . Astyanax xavante is distinguished from all other congeners by the following combination of characters: two vertical, brown humeral spots, a brown stripe on the flank, a black spot on the middle caudal-fin rays, 19 to 23 branched anal-fin rays, 34 to 37 perforated scales on lateral line, larger body depth (35.5-40.2% of SL) in about two to three scales ahead of dorsal-fin origin, head length 28.4-31.2% of SL, head not massive, interorbital width 34.5-39.4% of HL, snout not abruptly tapered, distance from snout to origin of dorsal fin 50.0-56.0% of SL, one to three maxillary teeth, five tetra- to heptacuspidate premaxillary inner row teeth, four, large, pentato heptacuspidate, and four to nine, small uni-, bi-, tri- or pentacuspid, dentary teeth, anal-fin origin on vertical through posterior third of dorsal-fin base, and fin ray hooks in mature males absent.

Description. Morphometric and meristic data of holotype and paratypes presented in Table 1. Larger specimen 59.6 mm SL. Body compressed and elongate; larger depth in about two to three scales ahead of dorsal-fin origin. Preventral and predorsal areas rounded. Dorsal and ventral body portions unequal, first shallower when verified by imaginary horizontal line passing through buccal opening. Dorsal profile straight between snout and occipital process; slightly convex from this point to base of dorsal-fin origin; straight from there to caudal-fin, slightly concave at limits of dorsal and adipose fins. Ventral profile smoothly convex from snout up to slightly behind pectoral-fin origin; straight from that point to anal-fin origin; straight at base of anal fin and straight from there to caudal fin.

Mouth terminal and horizontal. Snout smaller than eye diameter. Upper jaw slightly longer than lower jaw. Upper jaw larger than orbital diameter.

Dorsal-fin origin at middle or posterior to middle of standard length; when adpressed its distal extremity reaches fourth scale anterior to adipose-fin origin; distal border smoothly rounded; ii,9 rays. Caudal fin naked and forked, with symmetric or slightly asymmetric lobes with lower lobe somewhat larger; extremities slightly round; i,17,i rays. Distal pectoral border smoothly rounded; distal extremity surpasses pelvic fin origin in larger specimens (larger than about 40 mm SL), but not in smallest specimens; i,10-12 * rays. Pelvic-fin origin anterior to vertical line through dorsal-fin origin; distal border smoothly rounded; tip not reaching anal-fin origin; i,6 * - i,7 rays. Anal fin origin on vertical through posterior third of dorsal fin base; distal border smoothly convex (usually) or straight in anterior third, and smoothly convex (usually) or smoothly concave posteriorly; iii-v(iv *),19-23(20 *) rays (total: 23-26).

Dorsal procurrent rays 12(3); ventral procurrent rays 10(3). Vertebrae 35(1) or 36(2). Gill-rakers on first branchial arch 7+1+10(1), 8+1+9(1), or 8+1+10(1). Supraneurals 4(2) or 5(1).

Scales cycloid, not very thick. Lateral line complete, 34- 37(36*) perforated scales. Transverse rows of scales 12- 14(13*); above lateral line 6-7* rows; below lateral line 5*-6 rows. Scales sheath along anal fin base covering bases of unbranched rays and about ten first branched rays. Predorsal scales 11-14 in regular series.

Dentary with 4 larger teeth, followed by 4 to 9 small teeth ( Fig. 2 ). Larger teeth penta- to heptacuspidate. In some specimens, first small tooth (fifth tooth counted from mandibular symphysis) more developed than following ones, although distinctly smaller than preceding four teeth. Small teeth uni-, bi-, tri-, and pentacuspidate. Premaxilla with two tooth rows. Inner row with 5 (rarely 4) teeth: tri- to heptacuspidate. Outer row with 4 (rarely 3 or 5) teeth: tri- and pentacuspidate. Maxilla with 1 to 3 teeth, tri- and pentacuspidate. Cuspids of different sizes, central always larger than lateral and arranged in straight line.

Coloration in life. Brownish background ( Fig. 3 ). Dorsum of head and trunk brown. Side of head cream. Flank brownish above lateral line; lower flank greenish-silver. Branchiostegal region and ventral trunk area whitish. Two vertical brown diffuse humeral spots. First spot located between 2 nd and 6 th scales behind opercle margin; its depth includes three scale rows above and two below lateral line. Second humeral spot located 2-3 scales posterior to first spot; pale, bar-shaped area between both spots. Pale areas also anterior to and below humeral spots. Lateral wide stripe brownish, with diffuse shape on body flank, including 1 st, 2 nd and 3 rd scale rows above and 1 st scale row below (this on vertical through about half of anal-fin) lateral line. Middle caudal rays black from 7 th to 11 th or 12 th rays, including their extremities.

Proximal half of dorsal fin yellowish and blackish on distal half of first 3-5 branched rays. Proximal anal fin yellowish and distal half orangish-yellow, with black border, especially on anterior and middle thirds.Adipose and pectoral fins yellowish. Proximal half of pelvic fin yellowish and orangish-yellow on distal halves of rays. Distal upper and lower caudal-fin lobes reddish, and middle rays yellowish. Dark spot on pupil.

Coloration in alcohol. Background slightly brownish with wide brown diffuse stripe on flank, usually from second humeral spot to caudal fin base; its width encompassing 1 st, 2 nd and 3 rd scale rows above and 1 st scale row below (this on vertical through about half of anal fin) lateral line. Dorsum and upper lateral head regions dark brown; head lower lateral and branchyostegal region cream or slightly whitish. Dorsum trunk dark brown, lateral upper dorsal trunk greenish-brown, and lower lateral whitish-brown. Ventral trunk cream or slightly white.

Conspicuous brown first humeral spot, similar to somewhat diffuse, inverted triangle shape, width about four-five scales and depth of about five scales, two below and three above lateral line. Inconspicuous or faint second bar-shaped brownish humeral spot little behind first humeral spot, sometimes mixed with brown lateral stripe; pale or whitish anterior areas between and below humeral spots. Black middle caudal rays, from 7 th to 11 th or 12 th, with its extremities included.

Dorsal fin hyaline or translucent, blackish or not, on distal half of first three-five branched rays. Anal fin hyaline or translucent, with blackish ray tips. Caudal-fin lobes slightly blackish or translucent; middle caudal rays black. Adipose, pectoral, and pelvic fins hyaline, translucent or slightly blackish. Pupil with dark spot.

Habitat and ecological notes. Astyanax xavante inhabits crystalline water streams with flow from 0.05 to 0.70 m 3 /s. There is a reduced number of pools along these watercourses, but there are many rapids and accentuated falls, some up to 30 m high. The bottom of the rapids is generally composed of stone and gravel-stone. Sand and small silt and clay fractions prevail at the bottom of the pools. In general, the rapids are typical of mountain streams with fast-flowing water and gravel, rocky, and sandy bottoms. The banks are covered by riparian forest which prevents most light penetration and have little or no marginal herbaceous vegetation. There are many exposed roots from erosion and many tree trunks, branches and submerged leaves, in various stages of decomposition. The fishes preferentially occupy the water surface and the spaces among roots and branches. They usually form schools with up to two dozen individuals, but schools with about 150 individuals have also been observed. They are more abundant in the upper and middle courses of the córrego Avoadeira, and their frequency decreases downstream.

Astyanax xavante is seemingly the only species inhabiting above the cachoeira Pé da Serra, the lowest of all twelve waterfalls at this creek. Astyanax xavante was collected about 0.5 km below that waterfall syntopically with A. argyrimarginatus , A. asuncionensis , A. elachylepis , Knodus sp. (Characidae) , and Aequidens tetramerus (Cichlidae) , despite the reduced frequency of the latter. All the collections were conducted in the daytime.

Astyanax xavante is an opportunistic omnivorous fish. Studies on the feeding ecology of this species have shown that from a total of 357 examined stomachs, 90.4% contained some kind of food and 9.6% were empty. A lot of food of allochthonous origin, primarily composed of terrestrial insects (Hymenoptera, present in 29% of the stomachs; Diptera, 14.1%; Homoptera, 4.2%; and Hemiptera, 3.7%) was found in the stomachs, as well as materials of plant origin. Mainly leaves, small pieces of wood, tips of roots, flowers, fruits, and seeds were present in 48% of the stomachs examined. The majority of autochthonous foods identified were composed of aquatic insects (mainly adults, larvae and nymphs of Odonata, Trichoptera and other insects) present in 18% of the stomachs examined, and mites observed in 4.2% of the stomachs. Other food items found in smaller proportions were Ostracoda crustaceans. Filamentous algae were found in 12.3% of the individuals. Fish scales were observed in 9.3% of the total samples with food, and Protista in 2.8%, reinforcing the opportunistic behavior of these fish.

Studies conducted on 357 fish specimens during the dry season (July to October 1992) and flooded season (February and March 1993) showed individuals in all stages of sexual maturity, except for the specimens collected on July 19, 1992, when all individuals were ready for spawning. Fish ready for spawning were found in all collections, as well as many small, young specimens. The gonads, although mature, had a small number of oocytes compared to other mature fish. Thus, it seems evident that A. xavante has a long spawning period. The highest percentages of sexually mature individuals occurred in the dry months. The smallest mature male specimen had 26 mm SL; the smallest female, 25 mm SL.Hooks in the male fins were not seen in any reproductive phases.

Geographical distribution. Known from the type locality, córrego Avoadeira, a middle rio Araguaia tributary located in the Parque Estadual da Serra Azul , Barra do Garças , Mato Grosso. Serra Azul is located in the extreme south of the Serra do Roncador , at the beginning of the great Central Brazilian

Plateau, whose direction is mainly south-north.

Etymology. The specific epithet xavante is a reference to the Xavante ethnic group, constituted by the natives inhabiting the Serra do Roncador and middle rio Araguaia, Mato Grosso, Brazil. A noun in apposition.

Popular name. “Pe’auptabi” in Xavante language.

Figures

Fig. 1. Astyanax xavante, MZUSP 100375, 57.3 mm SL, holotype, from creek tributary of the córrego Avoadeira, rioAraguaia basin (approx. 15o53’S 52o15’W), Barra do Garças, Mato Grosso, Brazil.

Fig. 2. Astyanax xavante, ICLMA 503, 35.0 mm SL, non-type, lateral view of left side of upper and lower jaw teeth, scale = 5 mm (DEN:dentary; MX:maxilla; PMX:premaxilla).

Fig. 3. Astyanax xavante, MZUSP 100376, 47.3 mm SL, paratype, from córrego Avoadeira, rioAraguaia basin, Barra do Garças, Mato Grosso (upon capture).