Hyphessobrycon hamatus, Bertaco & Malabarba, 2005

Bertaco, Vinicius A. & Malabarba, Luiz R., 2005, A new species of Hyphessobrycon (Teleostei: Characidae) from the upper rio Tocantins drainage, with bony hooks on fins, Neotropical Ichthyology 3 (1), pp. 83-88 : 84-86

Hyphessobrycon hamatus , new species Figs. 1-2

Holotype. MCP 34000, 43.1 mm SL, male; Brazil, Goiás, Mambaí, córrego Cana Brava, tributary of rio Vermelho , rio Tocantins drainage, 14 o 29’S 46 o 6’W, 17 Dec 2002, Centro de Biologia Aquática - Universidade Católica de Goiás (UCG).

Paratypes. Brazil, Goiás, Mambaí: MCP 33930, 10 (6 males, 1 c&s male, 3 females), 26.7-44.8 mm SL, 8 Sep 2002, MCP 33931, 6 (2 males; 1 male c&s; 3 females), 32.0- 39.9 mm SL, same locality as holotype. MCP 33929, 11 (5 males; 6 females), 29.0- 40.1 mm SL, MZUSP 84411 , 6 (2 males, 4 females), 29.4-36.6 mm SL, córrego Jataí, 14 o 29’S 46 o 6’W, 8 Sep 2002, Centro de BiologiaAquática , UCG .

Diagnosis. Hyphessobrycon hamatus is distinguished from all species of the genus, except H. socolofi Weitzman and H. erythrostigma (Fowler) , by the presence of small bony hooks on the dorsal, anal, pelvic, and pectoral fins of males. The new species differs from H. socolofi and H. erythrostigma in the lower number of anal-fin rays (iii-v, 16-18, = 17, n = 28) versus (iv, 28-30 and iv, 27-29, respectively), and by the absence of a black spot on dorsal fin versus the presence of such pigmentation.

Description. Morphometric data for Hyphessobrycon hamatus are summarized in Table 1 . Body compressed and moderately deep; greatest body depth anterior to dorsal-fin origin. Dorsal body profile convex from nostril to dorsal-fin origin; posteroventrally slanted at dorsal-fin base; straight from last dorsal-fin ray to adipose-fin origin. Ventral profile of head convex. Ventral body profile convex from pectoral-fin origin to anal-fin origin. Body profile along anal-fin base straight and posterodorsally slanted. Caudal peduncle elongate, nearly straight to slightly concave along both dorsal and ventral margins.

Snout convex from margin of upper lip to vertical through anterior nostrils, straight from that point to tip of supraoccipital spine. Head small. Mouth terminal. Maxilla extending anteriorly to under middle of orbit, slightly curved, and aligned at approximately 45 degrees angle relative to longitudinal axis of body. Anterodorsal border of maxilla concave, posterodorsal border slightly convex, anteroventral border concave, and posteroventral border convex. Maxilla slightly widened posteriorly.

Premaxilla with two tooth rows; outer row with 3-4, rarely 5, tricuspid teeth with central cusp larger; inner row teeth 4-5, gradually decreasing in length from first to fourth teeth, last tooth considerably smaller with 3-5 cusps and central cusp longer and broader than other cusps. Two, rarely 3 maxillary teeth, with 3-5 cusps, central cusp slightly longer. Three or 4 anterior most dentary teeth larger, with 4-5 cusps, followed by medium sized tooth with 3-5 cusps, and 5-6 smaller teeth with 1-3 cusps or conical in shape; central cusp in all teeth two to three times longer and broader than remaining cusps. Cusp tips slightly curved posteriorly and towards inside of mouth.

Dorsal-fin rays ii, 9 (three specimens with ii, 8; n = 28); first unbranched ray approximately one-half length of second ray. Males with bony hooks in distal one-third of first to fifth branched rays. Dorsal-fin origin located posterior to middle of SL and posterior to vertical through pelvic-fin origin. Adipose-fin located approximately at vertical through insertion of last anal-fin ray.

Anal-fin rays iii-v, 16-18 (= 17, n = 28). First unbranched ray usually only apparent in cleared and stained specimens. Anal-fin profile slightly concave in females and males. Longest branched rays of depressed anal fin reaching origin of last anal-fin ray. Anal-fin origin located posterior to vertical through base of last dorsal-fin ray. Anal-fin rays of males bearing one pair of small, narrow, bony hooks along posterolateral border of each segment of lepidotrichia, usually along last unbranched two rays and ten anterior branched rays; hooks more numerous along second through fifth branched rays, rarely present on eleventh ray. Hooks usually located along posterior most branch and distal 1/2 to 2/ 3 of each ray.

Pectoral-fin rays i, 9-12, rarely 10 or 13 (= 10.8, n = 28). Males with bony hooks on distal portion of unbranched and first to sixth branched rays. Pelvic-fin rays i, 6-7 (usually i, 7; n = 28). Pelvic-fin origin located anterior to vertical through dorsal-fin origin. Pelvic fin of males usually bearing 1 bony hook per segment of lepidotrichia along ventromedial border of first to fifth branched rays.

Caudal-fin forked, with 19 principal rays without bony hooks. Dorsal procurrent rays 11. Ventral procurrent rays 10.

Scales cycloid, moderately large. Lateral line incomplete, perforated scales 10-32 (= 25.6, n = 27). Longitudinal scale series including lateral-line scales 33-35 (= 34.1, n = 28). Scale rows between dorsal-fin origin and lateral line 5-6 (usually 6, = 5.9, n = 28); scale rows between lateral line and pelvic-fin origin 4-5 (usually 5, = 4.7, n = 28). Predorsal scales 11-13, usually 12, arranged in regular series (= 12.1). Scales rows around caudal peduncle 14-15 (= 14.1). Scale sheath along anal-fin base with 5-7 scales in single series, extending posteriorly to base of fourth to sixth branched rays.

Precaudal vertebrae 16; caudal vertebrae 17; total vertebrae 33. Supraneurals 6. Gill-rakers 6-7/11 (n=2).

Color in alcohol. Dorsal and dorsolateral portions of head and body dark brown. Infraorbital and opercular areas covered with scattered, dark chromatophores. Scales on lateral and ventral surface of body bordered with dark brown chromatophores. Anterior humeral spot very discrete, vertically-elongate, and narrowing ventrally, located over second to third lateral-line scales and extending over 5-6 horizontal series of scales including lateral line. Second humeral spot diffuse, located nearly above 7th-8th lateral line scale and at anterior end of midlateral stripe, and extending usually over 2-3 horizontal series of scales above lateral line. Faint midlateral body stripe extending from second humeral spot to tip of median caudal-fin rays, becoming gradually wider and more intensely pigmented towards caudal peduncle. Midlateral body stripe slightly expanded dorsally and ventrally along caudal peduncle and caudal-fin base and forming small spot ( Fig. 1 ).

Sexual dimorphism. Males of H. hamatus are easily recog-

nized by the presence of bony hooks on the dorsal-, pectoral-, anal- and pelvic-fin rays.

Distribution. Hyphessobrycon hamatus is known only from two tributaries of the rio Vermelho, in the headwaters of the rio Tocantins basin, Mambaí, Goiás, Brazil.

Etymology. The specific epithet hamatus is from the Latin, meaning hooked, referring to the presence in males of hooks on all fins, except the caudal fin.

Ecological notes. All specimens of H. hamatus were caught in lentic stretches of shallow streams with sand and scattered stones on the bottom, and moderate amount of riparian vegetation. Species collected with H. hamatus were Ancistrus sp., Astyanax sp., Cetopsorhamdia sp., Characidium sp., Knodus sp., and Trichomycterus sp.

Figures

Fig. 1. Hyphessobrycon hamatus, MCP 34000, holotype, male, 43.1 mm SL; Brazil, Goiás, Mambaí, córrego Cana Brava, tributary of rio Vermelho.

Fig. 2. Hyphessobrycon hamatus, MCP 33930, paratype, 38.3 mm SL.SEM photograph of rightside maxillary (top), premaxillary (middle), and dentary (bottom) teeth.