Astyanax jacobinae, Zanata, Angela M. & Camelier, Priscila, 2008

Zanata, Angela M. & Camelier, Priscila, 2008, Two new species of Astyanax (Characiformes: Characidae) from upper rio Paraguaçu and rio Itapicuru basins, Chapada Diamantina, Bahia, Brazil, Zootaxa 1908, pp. 28-40 : 34-36

Astyanax jacobinae , new species

Figs. 4 , 5

Holotype. MZUSP 89570 (50.8 mm SL), Brazil, Bahia, Jacobina, Itaitu village, rio da Jaqueira below Cachoeira Araponga, tributary of rio Itapicuru-mirim, rio Itapicuru basin, 11°22’19.8’’N, 40°29’39.7’’W, 535 m alt.; Zanata et al., 13 June 2005.

Paratypes. Collected with holotype. UFBA 0 2793 (5, 22.8–38.2 mm SL; 1 c&s, 32.2 mm SL). MZUSP 89571 (3 R, 27.1–32.0 mm SL).

Diagnosis. Astyanax jacobinae can be distinguished from most of its congeners and from all other Astyanax species known from northeastern Brazilian drainages ( A. brevirhinus , A. fasciatus , A. intermedius , A. lacustris , A. pelecus , A. rivularis , A. taeniatus ) by the presence of a vertically elongated humeral blotch (vs. distinctly horizontally elongated humeral blotch in A. lacustris and A. pelecus ), absence of a conspicuous dark stripe from humeral region to caudal peduncle (vs. well defined dark midlateral stripe along most of body length in A. intermedius , A. pelecus , A rivularis , A. taeniatus ), three or four outer premaxillary teeth, three maxillary teeth, and 21–26 anal fin rays (vs. five outer premaxillary teeth, one or two maxillary teeth, and 28 anal-fin rays in A. brevirhinus ). The new species differs from the majority of Astyanax species by its larger eye diameter (36.8–40.3% vs. 24.7–35.4%, with the exception of A. intermedius among northeastern species that approaches the eye diameter of A. jacobinae with 29.0–36.4%). Astyanax jacobinae can be further distinguished from A. intermedius by having higher number of branched anal-fin rays (19–22 vs. 16–18), shorter distance from snout to anal-fin origin (61.4–64.4% vs. 66.2–68.3%), and longer anal-fin base length (27.6– 30.7% vs. 21.6–24.8%). Can be further distinguished from A. rivularis by having lower number of perforated scales (34–37 vs. 39) and three maxillary teeth (vs. one or two). Also differs from A. taeniatus by having three maxillary teeth (vs. two) and by having lower number of cusps on teeth (usually five vs. usually seven cusps, even on maxillary teeth). Astyanax jacobinae can be further diagnosed from specimens of A. fasciatus from São Francisco and Paraná rivers by the absence of a conspicuous caudal blotch, by having three maxillary teeth, and dentary teeth decreasing gradually in size (vs. presence of a well defined caudal blotch, one maxillary teeth, and dentary with four larger teeth followed by a number of small ones). This new species distinguishes from A. turmalinensis by its higher number of maxillary teeth and by the presence of only one humeral blotch (3 or 4 teeth vs. 1 or 2 and presence of two humeral blotches).

It can be also distinguished from A. epiagos by having higher number of branched anal-fin rays (19–22 vs. 13–17), three maxillary teeth (vs. 0–2), longer anal-fin base length (27.6–30.7% vs. 18.1–23.2%), shorter distance from eye to dorsal-fin origin (36.0–39.2% vs. 39.5–43.2%), and also by the absence of broad space between infraorbitals and preopercle (see under ‘Discussion’ for diagnosis of the species from “ A. scabripinnis species complex”).

Description. Morphometric data of the holotype and paratypes are presented in Table 1 . Body compressed, moderately elongate. Greatest body depth located along vertical through posterior portion of pectoral fin. Dorsal profile of head convex from upper lip to vertical through anterior nostrils; straight to slightly concave from latter point to tip of supraoccipital spine and convex from this point to dorsal-fin origin. Body profile along dorsal-fin base straight and posteroventrally inclined; straight from dorsal-fin base terminus to adipose fin; slightly concave between latter point to origin of dorsalmost procurrent caudal-fin ray. Ven t ra l profile of body convex from tip of lower lip to anal-fin origin. Body profile along anal-fin base straight and posterodorsally inclined. Ventral profile of caudal peduncle nearly straight to slightly concave.

Mouth terminal. Posterior terminus of maxilla extending beyond anterior margin of orbit. Premaxillary and dentary teeth massive, cusps distributed in a gently arch facing oral cavity. Premaxillary teeth in two rows. Outer row with 3* (8) or 4 (1) teeth bearing 3 or 5 cusps. Inner row with 5 (9) teeth bearing 4 to 7 cusps. Symphyseal tooth of inner series asymmetrical, with one cusp on anteromedial side, one larger central cusp and two smaller on lateral side, second teeth the larger, with 7 cusps in the holotype, followed by teeth with 5 cusps; smaller specimens with a maximum of 5 cusps. Maxilla with 3 (9) teeth bearing 5 cusps; teeth similar in size. Dentary with 11 (1) or 12* (1) symmetrical teeth; anteriormost ones broad and similar in size, with 5 or 7 cusps, followed by teeth with 5 cusps and posterior teeth with 1 or 3 cusps. Dentary teeth decreasing gradually in size and number of cusps posteriorly.

Scales cycloid, circuli absent on exposed area of scales, with various divergent radii extending to posterior margin of scales. Lateral line slightly decurved anteriorly, completely pored from supracleithrum to base of caudal fin, with 35* (3), 36 (3), or 37 (1) perforated scales. Horizontal scale rows between dorsal-fin origin and lateral line 5 (2) or 6* (5), not including scale of predorsal series situated just anterior to first dorsal-fin ray. Horizontal scale rows between lateral line and pelvic-fin insertion 4* (7). Scales along middorsal line between tip of supraoccipital process and origin of dorsal fin 11* (6) or 12 (1). Horizontal scale rows around caudal peduncle 13 (2) or 14* (3). Single row of 3 to 5 scales covering base of anterior most anal-fin rays.

Dorsal-fin rays ii, 9 (9). Distal margin of dorsal fin straight. Dorsal-fin origin located slightly posterior to or on the middle of standard length. Base of last dorsal-fin ray aligned with vertical through anterior branched anal-fin rays. First dorsal-fin pterygiophore inserting behind neural spine of 11th* (2) vertebra. Adipose fin present. Anal-fin rays iv, 19* (3), 20 (4), 21 (1), or 22 (1). Distal margin of anal fin concave. First anal-fin pterygiophore inserting behind haemal spine of 17th * (3) or 18th (2) vertebra. Pectoral-fin rays i, 10* (3) or 11 (6). Contact of posterior extremity of pectoral and pelvic-fin insertion ontogenetically variable; pectoral fin not reaching vertical through pelvic-fin insertion of holotype but trespassing that point in specimens of 38.2 mm SL or smaller. Pelvic-fin rays i, 6* (3) or 7 (6). Caudal fin forked, lobes rounded, similar in size. Principal caudal-fin rays 10+9 (5). Eleven * (1) or 12 (1) dorsal procurrent caudal-fin rays and 8 (2) or 9* (2) ventral procurrent caudal-fin rays. First gill arch with 5 (1) + 1 (1) + 10 (1) rakers. Vertebrae 35* (3) or 36 (2). Supraneurals 5* (2) or 6 (1).

Color in alcohol. Ground color tan, usually ventral and dorsal half of body similarly darkened. Dark chromatophores densely concentrated on dorsal surface of head from upper lip to supraoccipital spine. Middorsal portion of body dark. Small, dark chromatophores present on snout, entire maxilla and on portion of infraorbitals closer to the orbit. Distal portions of infraorbitals, mainly on third infraorbital, and areas of preopercle and opercle with relatively larger, scattered dark chromatophores. Ventral portion of head less pigmented, with scattered dark chromatophores spread throughout.

Scales of lateral portion of body with dark chromatophores almost homogeneously distributed over entire area, not forming a conspicuous reticulate pattern. Central portions of scales usually with smaller chromatophores. Region comprised below lateral line, between cleithrum and anal-fin origin, slightly clearer. Humeral region with a vertically-elongated blotch, extending from two horizontal series of scales above lateral line to about one or one and a half scales below it. Humeral blotch bordered anteriorly and posteriorly by clearer areas. Caudal peduncle with inconspicuous dark mark, more visible in specimens around 30.0 mm SL.

Dorsal, anal, and caudal fins darkened. Dorsal and caudal fins with dark chromatophores somewhat homogeneously distributed over rays and interradial membranes. Anal fin darkened in a pattern similar to that of dorsal fin, but with dark pigmentation distinctly more developed over interradial membranes and on borders of rays. Pectoral and pelvic fins clearer, with dark chromatophores only over borders of rays. Adipose fin covered with small dark chromatophores. Caudal fin with dark chromatophores somewhat more concentrated on median four or five rays, but not configuring a well defined stripe.

Color in life. Freshly collected specimens had overall coloration silvery-tan, with silvery highlights on scales, major portion of iris, infraorbitals, preopercle, and opercle (fig. 5). Dorsal portion of iris, together with lateroventral half of head, with the exception of third infraorbital, and ventral portion of preopercle and opercle tinged with yellow. Scales around humeral spot and on lateroventral region of body anterior to anal fin origin also yellowish. Humeral spot visible, although not so conspicuous as in preserved specimens. Concentration of dark chromatophores visible over caudal peduncle, although not forming conspicuous blotch. Dorsal, anal, caudal, and adipose fins reddish-orange. Pectorals yellowish and pelvic fins hyaline.

Sexual dimorphism. Bony hooks on fins or other dimorphic characters were not found in the specimens examined.

Geographic distribution and ecological notes. Astyanax jacobinae was collected only in rio da Jaqueira, below Cachoeira Araponga (11°22’19.8’’N, 40°29’39.7’’W), a tributary of rio Itapicuru-mirim, rio Itapicuru basin (fig. 2). The type-locality of A. jacobinae is a dark headwater stream with mild water current running over pebbles, rocks and sand (fig. 6). Stream depth in the area sampled varied between 0.3–0.5 m and average width was around 2.0 m. Trees, palm trees, and grasses represented the marginal vegetation. The analysis of the stomach contents of one specimen revealed the presence of two distinct larvae of Diptera (Chironomidae) , larvae of Trichoptera, fragments of adults of Diptera and unidentified fragments of arthropods.

Popular name. Piaba.

Etymology. The name jacobinae refers to the type locality, município de Jacobina, BA, Brazil.

Figures

FIGURE 4. Astyanax jacobinae, new species, holotype, MZUSP 89570, 50.8 mm SL, Brazil, Bahia, Jacobina, rio Itapicuru basin.

FIGURE 5. Astyanax jacobinae, new species, holotype alive, MZUSP 89570, 50.8 mm SL.