Hyphessobrycon notidanos, Carvalho & Bertaco, 2006

Carvalho, Tiago Pinto & Bertaco, Vinicius Araújo, 2006, Two new species of Hyphessobrycon (Teleostei: Characidae) from upper rio Tapajós basin on Chapada dos Parecis, Central Brazil, Neotropical Ichthyology 4 (3), pp. 301-308 : 304-306

Hyphessobrycon notidanos , new species Figs. 4-6

Holotype. MCP 39511 (28.6 mm SL, male), Brazil, Mato Grosso, Comodoro, rio Doze de Outubro on road BR 364 between Comodoro and Vilhena, 12º58’39"S 60º00’30"W, 14 Jul 2004, R. E. Reis, P.A. Buckup, A. R. Cardoso & E. H. L. Pereira.

Paratypes. MCP 38676 (70, 3 males c&s, 10.4-27.2 mm SL) , MZUSP 89645 (15, 12.6-25.7 mm SL), collected with the holotype .

Diagnosis. Hyphessobrycon notidanos is distinguished from all remaining species currently assigned to Hyphessobrycon by the following combination of characters: dorsal fin elongate in mature males; vertically elongate humeral spot; 2-4 maxillary teeth; iii,8 dorsal-fin rays; and 16-21 branched analfin rays. Hyphessobrycon notidanos is similar to H. loweae Costa & Géry, 1994 but differs by number of unbranched dorsal-fin rays (iii,8 vs ii,9), number of scales in lateral line series (32-34 vs 30-31), and shape of caudal peduncle spot (chromatophores present only on longitudinal axis vs forming a lozenge-shaped spot).

Description. Morphometric data for Hyphessobrycon notidanos presented in Table 1. Body compressed and deep; greatest body depth anterior to dorsal-fin origin. Dorsal body profile almost straight from nostril to supraocciptal spine, convex from supraocciptal end to dorsal-fin origin; posteroventrally declined at dorsal-fin base; straight from last dorsal-fin ray to adipose-fin origin. Ventral profile of head convex. Ventral body profile also convex from pectoral-fin origin to anal-fin origin. Body profile along anal-fin base posterodorsally inclined. Caudal peduncle elongate, nearly straight to slightly concave along both dorsal and ventral margins.

Snout blunt. Head small. Mouth terminal. Maxillary tip anterior to vertical through middle of orbit, and positioned at approximately 45 degrees relative to longitudinal axis of body. Dorsal border of maxilla nearly straight, anteroventral border concave, and posteroventral border slightly convex. Maxilla slightly widened posteriorly.

Premaxilla with two tooth rows. Outer row with 2-3, tricuspid or pentacuspid teeth with central cusp larger. Inner row teeth 5 with 5-7 cusps and central cusp slightly longer and broader than other cusps; gradually decreasing in length from first to fourth teeth, last tooth considerably smaller. Two to 4 maxillary teeth, with 5-7 cusps, central cusp slightly longer. Five or six anteriormost dentary teeth larger, with 5-7 cusps, followed or not by 1-3 teeth with 2-3 cusps or conical in shape; central cusp in all dentary teeth two times longer and broader than remaining cusps. Cusp tips slightly curved posteriorly and lingually ( Fig. 5 ).

Scales cycloid, moderately large. Lateral line incomplete, perforated scales 6-9 (8*, one specimen with 10 scales, mean = 7.4, n = 23). Longitudinal scales series including lateral-line scales 32-34 (34*, mean = 32.9, n = 23). Scale rows between dorsal-fin origin and lateral line 6 (n = 23); scale rows between lateral line and pelvic-fin origin 4 (n = 23), one specimen with 5. Predorsal scales 9-12, arranged in regular series (11*, mean = 10.7, n = 23). Scales rows around caudal peduncle 14 (n = 17). Scale sheath along anal-fin base with 6-8 scales in a single series (6*, n = 23), extending posterior to base of fifth to seventh branched rays.

Dorsal-fin elongate in males, longest rays reaching end of adipose fin base; rays iii,8 most common count (iii,8*, only four specimens with ii,9, n = 40), smaller individuals sometimes with more than 3 unbranched rays; first unbranched ray almost one-half length of second ray. Third unbranched ray longer than second; when branched the ramification begins at tip of second unbranched ray. Dorsal-fin origin approximately in middle of body and posterior to vertical through pelvic-fin origin. Anal-fin rays iii-iv,17-20 (17*, one specimen with 16 and other with 21, mean = 18.1, n = 23). Anal-fin distal profile nearly straight. Anal-fin origin at vertical through base of last dorsal-fin ray. Tip of latest branched rays reaching or surpasses caudal peduncle in some specimens. Pectoral-fin rays i,9-10 (9*, rarely 8 or 11, mean = 9.4, n = 23). Pelvic-fin rays i,6 (n = 23). Change of larval pectoral-fin stage to juvenile rayed fin at about 12.3-13.5 mm SL. Pelvic-fin origin anterior to vertical through dorsal-fin origin and almost or reaching beginning of anal fin. Caudal-fin forked, with 19 principal rays, sometimes with 18 or 20 rays (19*, n = 24). Dorsal procurrent rays 10-13 (n = 3). Ventral procurrent rays 9-12 (n = 3). Adipose fin present.

Precaudal vertebrae 15; caudal vertebrae 17-19; total vertebrae 32-34. Supraneurals 4. Gill-rakers 6/11 (n = 3).

Color in alcohol. Overall body coloration pale to yellowish. Dorsal portions of head and body dark brown. Ventral, infraorbitals and opercular areas covered with scattered, dark chromatophores. One longitudinal stripe beginning at posterior orbital margin, not conspicuous at this portion, and reaching tip of median caudal-fin rays. Stripe narrow below dorsal fin and larger but quite diffuse on posterior portion of body. A light, very conspicuous, yellowish band without dark chromatophores between dorsolateral scales and longitudinal stripe. One triangular and vertically elongate black humeral spot, with dorsal portion wider. Humeral spot located over second to fifth scale of lateral line and extending vertically on that region over the scales of three longitudinal series, including lateral line. A more or less distinct rounded and horizontally elongated blotch on caudal peduncle. Small black chromatophores scattered over rays of all fins. Anal fin with small black chromatophores along its distal border forming a narrow stripe. Concentrated dark pigment on tip of pelvic fins and unbranched dorsal-fin rays in some specimens. Black pigments forming a stripe on 4-5 median caudal-fin rays ( Fig. 4 ).

Color just after fixation. Color pattern similar to described for alcohol preserved specimens. Specimens examined soon after fixation in formalin, have all fins and body with red to yellowish pigments ( Fig. 6 ).

Ecological notes. The type specimens of H. melanostichos and H. notidanos were collected close to the margin along semilentic stretches of a shallow river with clear water, sand and scattered small stones on the bottom, with moderately submersed and riparian vegetation. Some specimens of H. melanostichos (MCP 39808, 6 of 110, 13.0- 26.3 mm SL) presented kyphotic lordosis. These abnormalities are similar to described in several specimens of Astyanax alburnus (Hensel, 1870) (= Cyanocharax alburnus ) from the lago Guaíba, laguna dos Patos system, southern Brazil ( Flores-Lopes et al., 2002), caused by infection of metacercarial cysts of digenetic trematodes in the vertebral column.

Sexual dimorphism. Four males dissected and identified by observation of the testes. Dorsal fin elongate, reaching posteriorly to base of adipose fin. Mature males not presents gill gland on first gill arch.

Distribution. Hyphessobrycon notidanos its known only from the type locality: rio Doze de Outubro, tributary of rio Juruena, in the headwaters of the rio Tapajós basin, Chapada dos Parecis, Comodoro, Mato Grosso, Brazil.

Etymology. The name specific notidanos , from Greek, with pointed dorsal fin, referring to the elongate dorsal-fin rays in males.

Figures

Fig. 4. Hyphessobrycon notidanos, MCP 39511, holotype, 28.6 mm SL; male, rio Doze de Outubro, tributary of rio Juruena, rio Tapajós basin, Mato Grosso, Brazil.

Fig. 5. Hyphessobrycon notidanos, MCP 38676, paratype, 26.3 mm SL. Scanning electron microscope photograph of right side upper and lower jaws.

Fig. 6. Hyphessobrycon notidanos, MCP 38676, paratype, 25.7 mm SL, male, color just after fixation.