A review of the Cis-Andean species of Hemibrycon Günther (Teleostei: Characiformes: Characidae: Stevardiinae), with description of two new species Bertaco, Vinicius A. Malabarba, Luiz R. Neotropical Ichthyology 2010 2010-12-31 8 4 737 737 3KLZQ Bertaco & Malabarba, 2010 Bertaco & Malabarba 2010 [919,1195,261,285] Actinopterygii Characidae Hemibrycon Animalia Characiformes 17 Chordata species mikrostiktos sp. nov.    Figs. 16-17     Holotype. MUSM 35490, 44.4 mmSL, río Aguaytía, río Negro, upper río Ucayalibasin, Aguaytía, Padre Abad, Ucayali, Peru, 09º02’34”S 75º30’45”W,  2 Nov 1999, P. de Rham& F. Chang.    Paratypes. MCP44521, 10(3 c&s), 27.6-42.4 mmSL; MUSM 15845, 19measured and counted of 187, 24.5-42.4 mmSL; UFRGS 12003, 10, 30.9-36.0 mm SL, collected with the holotype.   Diagnosis.  Hemibrycon mikrostiktosis readily distinguished from all congeners by the size of the humeral spot (2-3 vs. 4-9 horizontal series of scales), number of scale rows below of the lateral line (3-4 vs. 4-8), and total number of pelvic-fin rays (7 vs. 8). Furthermore,  H. mikrostiktosdiffers from most congeners by the number of branched anal-fin rays (18-21 vs. 21-34, and 17 in  H. tridens, Fig. 2), except  H. beniand  H. helleri. It differs from  H. beniand  H. helleriby the number of lateral line scales (40-42 vs. 44-53 and 42-44, Fig. 3).   Description.Morphometric data for  Hemibrycon mikrostiktossummarized in Table 4. Largest specimen 44.4 mmSL. Body compressed and moderately elongate; greatest body depth at vertical through middle length of pectoral fins. Dorsal profile of head nearly straight. Dorsal body profile convex from occipital bony to dorsal-fin origin; posteroventrally slanted at dorsal-fin base; straight from last dorsal-fin ray to adiposefin origin. Ventral profile of head convex. Ventral body profile convex from pectoral-fin origin to pelvic-fin origin, and straight to slightly convex to anal-fin origin. Body profile along analfin base posterodorsally slanted. Caudal peduncle short, nearly straight to slightly concave along dorsal and ventral margins. Snout rounded from margin of upper lip to vertical through anterior nostrils. Head relatively small. Mouth terminal, mouth slit nearly at horizontal through below middle of eye. Maxilla long and slightly curved, aligned at angle of approximately 45 oto longitudinal body axis, and its posterior tip extending below orbit, reaching nearly to vertical through center of eye. Premaxilla with two tooth rows; outer row with 4-6, tricuspid teeth with central cusp slightly longer; inner row with 4 pentacuspid teeth, gradually decreasing in length from first to third teeth and last tooth smallest; central cusp twice or three times longer and broader than other cusps. Maxilla toothed with 7-11 tri- to pentacuspid teeth, except for last three or four conical teeth, with central cusp longer. Three anteriormost dentary teeth larger, with 5 cusps, followed by medium sized tooth with 3 cusps, and 12-13 teeth with 1-3 cusps or conical; central cusp in all teeth two to three times longer and broader than other cusps. Cusp tips slightly curved posteriorly and lingually ( Fig. 17). Dorsal-fin rays ii,8 (n = 20); first unbranched ray approximately one-half length of second ray. Dorsal-fin origin located posterior to middle of SL and posterior to vertical through pelvic-fin origin. First dorsal-fin pterygiophore  V. A. Bertaco & L. R. Malabarba755   Fig. 16.  Hemibrycon mikrostiktos, MUSM35490, holotype, 44.4 mm SL, upper río Ucayali basin, Peru. inserted between the neural spines of eleventh to twelfth vertebrae (n = 3). Profile of distal margin of dorsal fin convex. Adipose-fin located at vertical through insertion of last or posterior to last anal-fin ray. Anal-fin rays iii-iv,18-20 (two with 21, mode = 19, n = 20, Fig. 2). Anal-fin profile slightly concave in all specimens. First anal-fin pterygiophore inserted between the haemal spine of last precaudal vertebra and the first caudal vertebrae.Anal-fin origin approximately at vertical through insertion in the middle dorsal fin. Pectoral-fin rays i,9-10 (mode = 9, n = 20). Pectoral-fin tip reaching pelvic-fin origin. Pelvic-fin rays i,5,i (n = 15) or i,6 (n = 5). Pelvic-fin origin located 3-4 predorsal scales anterior to vertical through dorsal-fin origin. Caudal fin forked with 19 principal rays (n = 20); lobes similar in size. Basal portion of caudal-fin lobes covered with irregular scales and smaller than those of the body, following by one larger scale in each lobe. Dorsal procurrent rays 12-13 and ventral procurrent rays 12-14 (n = 3). Scales cycloid, moderately large. Lateral line complete with 40-42 (mode = 41, n = 16, Fig. 3).[Scale rows between dorsalfin origin and lateral line 6-7 (mode = 6, n = 18); scale rows between lateral line and pelvic-fin origin 3-4 (mode = 4, n = 18). Predorsal scales 14, arranged in regular series (n = 18). Scales rows around caudal peduncle 14 (n = 18). Axillary scale on pelvic-fin origin extends posteriorly covering 2-3 scales. Scale sheath along anal-fin base with 7-10 scales in single series, extending to base of most anterior branched rays. Precaudal vertebrae 17; caudal vertebrae 23-24; total vertebrae 40-41. Supraneurals 6-7 (n = 3). Gill rakers on upper limb of outer gill arch 5-6, and on lower limb 9-10 (n = 5).  Color in alcohol.Dorsal portion of head and body with dense concentration of black chromatophores. Dorsal and dorsolateral portion of caudal peduncle near caudal fin base densely pigmented. Dorsolateral portion of body with scattered black chromatophores. Snout and upper portion of maxilla densely pigmented. Infraorbitals and opercle with scattered black chromatophores. Midlateral body silvery and dark pigmented. One small black humeral spot, located over third to fourth lateral line scales and extending over 1-2 horizontal series of scales, sometimes including lateral line. Base of caudal fin and middle rays black pigmented. Abdominal region almost devoid of black chromatophores. Dorsal, adipose, anal and caudal fin with dark pigmentation diffuse. Pectoral and pelvic fins hyaline ( Fig. 16).  Sexual dimorphism.None of the typespecimens examined had hooks on fins or any other apparent sexually dimorphic features. Gill glands were not found on first gill arch.   Distribution.  Hemibrycon mikrostiktosis known from río Aguaytía, upper río Ucayalidrainage, Ucayali, Peru( Fig. 4).   Fig. 17.  Hemibrycon mikrostiktos, MCP44521, paratype, female, 35.7 mm SL. Scanning electron micrograph of left side upper and lower jaws. Scale bar = 1 mm. 756 A review of the Cis-Andean species of  Hemibrycon   Etymology.The name  mikrostiktosis from the Greek, mickros, small, and stiktos, spot, referring to the small humeral spot. A noun in apposition. 1999-11-02 MUSM P. de Rham & F. Chang. Peru Padre Abad -9.042778 rio Aguaytia 21 -75.5125 Aguaytia 17 MUSM 35490 1 Ucayali holotype MCP 44521 [809,1451,486,507] MCP, MUSM 17 10 1 paratype [809,1450,515,536] UFRGS 17 19 1 paratype [809,1372,543,564] UFRGS 17 10, 30.9 1 holotype