Astyanax epiagos, 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: 29-33

publication ID 10.5281/zenodo.274537

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scientific name

Astyanax epiagos

new species

Astyanax epiagos  , new species

Fig. 1View FIGURE 1

Holotype. MZUSP 89568 (59.3 mm SL), Brazil, Bahia, Morro do Chapéu, rio Ferro Doido, above Cachoeira do Ferro Doido, tributary of rio Jacuípe, Paraguaçu drainage, 11 ° 37 ’34.0’’N, 41 °00’ 11.5 ’’W, 899 m alt.; Zanata et al., 10 June 2005.

Paratypes. All from Brazil, Bahia, Morro do Chapéu. UFBA 0 2792 (344, 3 c&s, 14.0– 52.6 mm SL). MZUSP 89569 (20, 23.7–42.6 mm SL). ANSP 189081 (20, 25.6–42.5 mm SL); collected with holotype. UFBA 0 2794 (6, 26.9–36.6 mm SL), tributary of rio Jacuípe 4 km from Morro do Chapéu, 41 °07’ 13.’’N, 11 ° 34 ’ 20.7 ’’W, 934 m alt.; Zanata et al., 10 June 2005.

Diagnosis. Astyanax epiagos  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  , and A. taeniatus  ) by a vertically elongated humeral blotch and body highest along vertical through midlength of pectoral fin (vs. distinctly horizontally elongated humeral spot and highest body depth just anterior  to dorsal-fin origin in A. lacustris  and A. pelecus  ), absence of 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  ), 2–4 outer premaxillary teeth and total anal fin rays 17–21 (vs. 5 teeth and 28 anal-fin rays in A. brevirhinus  ). Astyanax epiagos  can be further distinguished from A. rivularis  by having lower number of perforated scales (35–36, rarely 34 or 37, vs. 39 scales), lower number of branched anal-fin rays (13–17 vs. 19), lower number of maxillary teeth (0–2 vs. 3–4), and shorter upper jaw length (31.6–41.4 % vs. 45.1–47.7 %). It can be also distinguished from A. intermedius  by its slender body, with longer distance between posterior margin of eye and dorsal-fin origin (39.5–43.2 % vs. 33.7–38.2 %), longer distance from dorsal-fin origin to caudal-fin base (45.7–52.7 % vs. 53.0– 54.2 %), and narrower humeral blotch. The new species differs further from A. taeniatus  by its lower number of branched anal-fin rays (13–17 vs. 19–24) and lower number of cusps on teeth (usually three to five vs. usually seven cusps, even on maxillary teeth) and from A. pelecus  by its lower number of lateral line scales (35–36, rarely 34 or 37, vs. 38–39 scales) and longer caudal peduncle length (13.3–16.6 % vs. 11.3–13.2 %). It can be further distinguished from A. fasciatus  by the absence of scales covering anal-fin rays base and body highest on vertical around midlength of pectoral fin (vs. presence of sheath of anal-fin scales and highest body depth just anterior  to dorsal-fin origin). Astyanax epiagos  can be distinguished from A. turmalinensis  by its relatively smaller eye diameter (26.2– 34.1 % vs. 31.1–39.7 %), absence of scales covering base of anal fin-rays (vs. presence), slender body, narrower humeral blotch, wider naked area between ventral margin of infraorbitals and preopercle and narrower and more conspicuous black blotch on caudal peduncle.

The new species is also distinguished from A. jacobinae  by the presence of conspicuous dark blotch over caudal peduncle, extending through median caudal-fin rays, smaller eye diameter (26.2–34.1 % vs. 36.8– 40.3 %), shorter anal-fin base length (18.1–23.2 % vs. 27.6–30.7 %), relatively longer caudal peduncle length (13.9–18.6 % vs. 12.2 –14.0%), longer distance from eye to dorsal-fin origin (39.5–43.2 % vs. 36.0– 39.2 %), and by having infraorbitals comparatively less developed, leaving broad space between these ossifications 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 somewhat compressed, robust, and elongate. Greatest body depth located around vertical through midlength 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 nearly straight to slightly convex from this point to dorsal-fin origin; profile of predorsal portion of body slightly convex in all its extension in specimens around 28.0 mm SL. Body profile straight to somewhat convex along dorsal-fin base; straight from dorsal-fin base terminus to adipose fin; slightly concave between latter point to origin of dorsalmost procurrent caudal-fin ray. Ventral profile of head and body convex from tip of lower lip to anal-fin origin. Body profile along analfin base straight and posterodorsally inclined. Ventral profile of caudal peduncle nearly straight to slightly concave.

Head obtusely rounded anteriorly in lateral profile; mouth terminal. Posterior terminus of maxilla extending slightly 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 2 (6), 3 * (20), or 4 (4) teeth bearing 3 or 5 cusps. Inner row with 4 (16) or 5 * (3) teeth bearing 4 to 7 cusps. Symphyseal tooth of inner series narrow, asymmetrical, with one cusp on anteromedial side, one larger central cusp and two smaller on lateral side, second teeth the larger, with 7 cusps, penultimate and last teeth with 4 cusps in two specimens and last teeth with 3 cusps in the other c&s specimen. Maxilla with 0 (2), 1 (21), or 2 * (6) teeth bearing 3 cusps. Dentary with 8 (3) somewhat elongate and symmetrical teeth, anterior  ones similar in size, with 5 cusps, antipenultimate with 3 cusps and two posteriormost abruptly smaller teeth with 1 cusp.

A. epiagos  A. jacobinae  Scales cycloid, circuli absent on exposed area of scales, with few slightly divergent radii extending to posterior margin of scales. Lateral line slightly decurved anteriorly, completely pored from supracleithrum to base of caudal fin, with 34 (1), 35 (9), 36 * (17), or 37 (1) perforated scales. Horizontal scale rows between dorsal-fin origin and lateral line 5 * (6) or 6 (23), 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 * (18) or 5 (12). Scales along middorsal line between tip of supraoccipital process and origin of dorsal fin 10 (1), 11 (6), 12 * (14), or 13 (5). Horizontal scale rows around caudal peduncle 13 (3) or 14 * (22). Base of anteriormost anal-fin rays not covered by series of scales.

Dorsal-fin rays ii, 9 (30). Distal margin of dorsal fin straight or slightly rounded. Dorsal-fin origin located slightly posterior to the middle of standard length. Base of last dorsal-fin ray anterior  to or aligned with analfin origin. First dorsal-fin pterygiophore inserting behind neural spine of 10 th (1), 11 th (2) or 12 th* (1) vertebra. Adipose fin present. Anal-fin rays iv, 13 (1), 14 (5), 15 (15), 16 * (8), or 17 (1). Distal margin of anal fin slightly concave to nearly straight. First anal-fin pterygiophore inserting behind haemal spine of 19 th (2) or 20 th (1) vertebra. Pectoral-fin rays i, 10 (4), 11 * (20), or 12 (5). Tip of pectoral fin not reaching vertical through pelvic-fin insertion. Pelvic-fin rays i, 6 (1) or 7 * (29). Caudal fin forked, lobes rounded, similar in size. Principal caudal-fin rays 10 + 9 (3). Nine (2), 10 (1) or 11 * (1) dorsal procurrent caudal-fin rays, and 9 * (3) ventral procurrent caudal-fin rays. First gill arch with 7 (3) + 1 (3) + 10 (2) or 11 (1) rakers. Vertebrae 34 (1), 35 (1), 36 (1), or 37 *(1). Supraneurals 5 (3).

Color in alcohol. Overall ground color tan, darker dorsally and yellowish ventrally. Dark chromatophores densely concentrated on dorsal surface of head from upper lip to supraoccipital spine. Small, dark chromatophores present over two first infraorbitals and anterior  half to two-thirds of maxilla. Remaining infraorbitals and opercle usually with larger dark chromatophores. Area situated between ventral borders of infraorbitals and border of preopercle relatively clearer, with small chromatophores sparsely distributed. Ventral portion of head less pigmented, with scattered dark chromatophores more concentrated on anteromedian area.

Scales of dorsal portion of body with dark chromatophores concentrated along its posterior margin resulting in a reticulate pattern; pattern usually reaching scale series immediately above pelvic-fin insertion. Central portion of scales with scattered, relatively large dark chromatophores, more densely distributed on dorsal half of body. Humeral region with a vertically-elongated, relatively narrow blotch not bordered anteriorly and posteriorly by clearer areas. Blotch extending over two horizontal series of scales above lateral line and one below it and covering one or one and a half scale from horizontal series above lateral line. Dark line poorly visible, extending from rear of humeral blotch to caudal peduncle. Relatively wide dark stripe on caudal peduncle, extending from area somewhat anterior  to vertical through adipose fin or just below the fin and reaching the posterior border of four or five median caudal-fin rays. Abdominal region without dark chromatophores.

All fin-rays darkened and small dark chromatophores scattered over clearer interradial membranes. Dorsal and anal fins somewhat darker. Anal fin of some specimens with higher concentration of dark chromatophores on distal border of rays. Pelvic fins hyaline or with few dark chromatophores forming interrupted lines over lateral borders of rays. Adipose fin darkened by small chromatophores.

Darker specimens with higher concentration of chromatophores over whole body, all fins and interradial membranes, and humeral and caudal spots not clearly visible.

Sexual dimorphism. Bony hooks on anal-fin rays were found in six male specimens examined (28.8– 42.8 mm SL). Hooks absent on remaining fins.

Geographic distribution and ecological notes. Astyanax epiagos  is known only from rio Ferro Doido, a tributary of rio Jacuípe, itself a tributary of the rio Paraguaçu, a coastal drainage of eastern Brazil (fig. 2). It was collected only above Cachoeira do Ferro Doido, a waterfall 98 meters high. According to extensive sampling efforts in other stretches of rio Ferro Doido the species is apparently absent below the waterfall and, indeed, absent in all others streams of Paraguaçu basin sampled. The species was collected exclusively in dark water streams, running over rocky bottom at elevate altitudes (899–934 m), in environment characterized by relatively small rocky pools (0.5 m deep and 1.5 m wide) connected by extremely shallow stretches of water or small rapids (fig. 3). The surrounding vegetation is characteristic of ‘Campo Rupestre’, with predominance of herbs and shrubs. The unique fish species collected with A. epiagos  and known to occur in the region is Hoplerythrinus unitaeniatus  .

The analysis of the stomach contents of six specimens revealed the presence of filamentous algae, fragments of vascular plants, adults and two distinct larvae of Diptera  ( Chironomidae  ), adults of Hemiptera and Coleoptera  ( Chrysomelidae  ), fragments of Hymenoptera and of other unidentified arthropods. Popular name. Piaba.

Etymology. The name epiagos  from the Greek, epi for above, and agos meaning rocky cleft, refers to the presence of the species on area above the waterfall and valley formed by rio Ferro Doido.

TABLE 1. Morphometric data for Astyanax epiagos, new species, MZUSP 89568, holotype, UFBA 0 2792 (n = 29), and for Astyanax jacobinae, new species, MZUSP 89570, holotype, MZUSP 89571 (n = 3), UFBA 0 2793 (n = 5).

    mean     mean
Standard length (mm) 59.3     50.8    
Depth at dorsal-fin origin 32.5     34.8    
Snout to dorsal fin origin 53.6     52.2    
Snout to pectoral-fin origin 26.6     26.8    
Snout to pelvic-fin origin 50.1 47.5–53.1   49.0    
Snout to anal-fin origin 66.6 63.1–69.0   64.4    
Caudal peduncle depth 12.3 10.3–12.6        
Caudal peduncle length 13.5 13.3–16.6   13.8    
Pectoral-fin length 20.2     20.1    
Pelvic-fin length 14.7     13.2    
Dorsal-fin base length 13.2     14.6    
Dorsal-fin heigth 23.4     25.2    
Anal-fin base length 22.8 18.1–23.2   27.6    
Anal-fin lobe length 14.7     18.9    
Eye to dorsal-fin origin 41.5     39.2    
Dorsal-fin origin to caudal-fin base 51.6     53.3    
Head length 24.5 24.1–29.2   26.8    
Horizontal eye diameter 26.2     36.8    
Snout length 24.8 21.8–27.7   22.1 21.0–26.4  
Least interorbital width 36.6     33.1    
Upper jaw length 41.4     41.2    

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