Astyanax pelecus, Bertaco & de Lucena, 2006

Bertaco, Vinicius A. & de Lucena, Carlos A. S., 2006, Two new species of Astyanax (Ostariophysi: Characiformes: Characidae) from eastern Brazil, with a synopsis of the Astyanax scabripinnis species complex, Neotropical Ichthyology 4 (1), pp. 53-60 : 56-57

Astyanax pelecus , new species

Figs. 1 , 4-5 , Table 1

Holotype. MCP 37570 (56.4 mm SL), rio Pardo on road BR116, Cândido Sales, Bahia, Brazil, 15º30’49"S 41º14’11"W, 21 Jan 1995, J. C. Garavello, S. A. Schaefer, A. S. Santos, J. P. da Silva & E. H. L. Pereira.

Paratypes. MCP 17919, 8 (1 c&s), 26.8-60.0 mm SL, collected with the holotype .

Diagnosis. The following combination of characters distinguishes Astyanax pelecus from its congeners: body depth (26.7-34.8% of SL), short but pointed snout, that is smaller than the orbital diameter, and reduced number of branched anal-fin rays (16-18). Furthermore, A. pelecus differs from other members of the genus in its distinctive color pattern: it possesses only one humeral spot limited to the region above lateral line series, and has a conspicuous midlateral body stripe extending from the upper margin of the opercle to the caudal-fin base, a putative autapomorphy of this species. Most of the remaining species of Astyanax have humeral spot vertically or horizontally elongate, with an extension of humeral spot ventral to lateral line and have the midlateral body stripe becoming faint or disappearing near, or just anterior to, humeral spot.

Description. Morphometric data summarized in Table 1 . Body compressed and elongate; greatest body depth usually situ-

ated anterior to dorsal-fin origin. Dorsal profile of head between vertical through posterior nostril and tip of supraoccipital spine straight or slightly convex. Body profile convex from tip of supraoccipital spine to base of last dorsal-fin ray, and straight from that point to adipose-fin origin. Ventral profile of body convex from margin of lower lip to anal-fin origin. Body profile along anal-fin base posterodorsally slanted. Caudal peduncle elongate and nearly straight to slightly concave along both dorsal and ventral margins.

Snout profile rounded from margin of upper lip to vertical through anterior nostrils. Head small. Mouth terminal or slightly sub-terminal with lower jaw slightly shorter than upper jaw. Maxilla extending posteriorly to vertical through anterior margin of orbit, slightly oblique, and at angle of approximately 45 degrees relative to longitudinal body axis. Anterodorsal border of maxilla concave, posterodorsal bor- der slightly convex, and ventral border convex. Maxilla slightly expanded anteroposteriorly.

Premaxilla with two tooth rows; outer row with two to four pentacuspid teeth with central cusp longer. Five or six teeth on inner row, gradually decreasing in length from first to fourth teeth and with last two teeth distinctive smaller. Teeth with five to seven cusps with central cusp twice as long and broad as other cusps. Maxilla with one to four (usually two) teeth with five to seven cusps and central cusp longer. Four or five anterior-most dentary teeth larger than other teeth, with seven cusps and followed by one or two medium sized teeth with five cusps, and six teeth with one to three cusps. Central cusp in all teeth two to three times as long and broad as other cusps. All cusp tips slightly curved posteriorly towards inside of mouth ( Fig. 5 ).

Dorsal-fin rays ii, 9 (n = 9); first unbranched ray approximately one-half length of second ray. Distal margin of dorsal fin straight or slightly convex. Dorsal-fin origin approximately at middle of SL. Adipose-fin located approximately at vertical through insertion of last anal-fin ray.Anal-fin rays iii-v, 16-18 (mean = 16.9, n = 9). First unbranched ray typically only apparent in cleared and stained specimens. Distal border of anal fin smoothly concave. Anal-fin origin located posterior to vertical through base of last dorsal-fin ray. Pectoral-fin rays i, 11-13 (mean = 12.1, n = 9). Tip of pectoral fin falls three or four scales short of vertical through pelvic-fin insertion. Pelvicfin rays i, 7 (n = 9). Pelvic-fin origin located slightly anterior to vertical through dorsal-fin origin. Tip of pelvic fin reaching posterior portion of genital opening, but falling short of analfin origin.

Caudal-fin forked with lobes of similar size and with 19 principal rays. Dorsal procurrent rays 11. Ventral procurrent rays 10 (n = 1).

Scales cycloid, moderately large. Lateral line complete. Scales in longitudinal series 38-39 (mean = 38.3, n = 9). Five scale rows between dorsal-fin origin and lateral line (n = 9); four scale rows between lateral line and pelvic-fin origin (n = 9). Eleven to twelve predorsal scales arranged in regular series (mean = 11.1). Fourteen scale rows around caudal peduncle (n = 9). Scale sheath along anal-fin base formed by four to six scales in single series and covering base of anterior-most rays.

Precaudal vertebrae 16; caudal vertebrae 19; total vertebrae 35. Supraneurals 5. Gill-rakers 6/8 (n = 1).

Color in alcohol. Dorsal and dorsolateral portion of head and body dark brown. Dorsal portion of body densely darkly pigmented in larger specimens. Scales on midlateral surface of body bordered with dark brown chromatophores forming reticulate pattern. Snout and anterior border of eye darkly pigmented. Body with black, strongly pigmented, midlateral stripe extending from upper edge of opercle to base of middle caudal-fin rays. Faint dark pigmentation present over middle caudal-fin rays. One small, diffuse dark humeral spot, present. Humeral spot sometimes obscured by midlateral stripe, located over third to fifth lateral line scales, and extending over one or two horizontal series of scales, including lateral line. Fins with scattered dark chromatophores ( Fig. 4 ).

rio Pardo, Cândido Sales, Bahia, Brazil.

Sexual dimorphism. Secondary sexual characters were not found on examined specimens.

Distribution. Astyanax pelecus is known from the upper rio Pardo drainage, at Cândido Sales, a coastal drainage in the state of Bahia, eastern Brazil ( Fig. 1 ).

Etymology. The species name is from the Greek pelekus, meaning axe, in allusion to the form of the dark pigmentation resulting from the junction of the humeral spot with the black midlateral stripe.

Ecological notes. During the dry season, the rio Pardo at the type-locality, is a large river, about 10-20 m wide, with clear water 0.1-1.0 m deep, alternating lentic stretches and rapids, with riparian vegetation that includes grasses. The bottom consists of stones, rocks, sand, and mud. Species collected with Astyanax pelecus were A. cf. bimaculatus , Astyanax sp., Apareiodon itapicuruensis , Characidium sp., Geophagus brasiliensis , Hoplias sp., and Parotocinclus cristatus .

Figures

Fig. 1. Coastal drainages of states of Espírito Santo and Bahia, eastern Brazil, showing the distribution of Astyanax microschemos (dot) and Astyanax pelecus (square).

Fig. 4. Astyanax pelecus, MCP 37570, holotype, 56.4 mm SL;

Fig. 5. Astyanax pelecus, MCP 17919, paratype, 51.3 mm SL. SEM image of right side upper and lower jaws teeth.