Hemibrycon polyodon ( Günther, 1864 )

Bertaco, Vinicius A. & Malabarba, Luiz R., 2010, A review of the Cis-Andean species of Hemibrycon Günther (Teleostei: Characiformes: Characidae: Stevardiinae), with description of two new species, Neotropical Ichthyology 8 (4), pp. 737-770 : 756-759

Hemibrycon polyodon ( Günther, 1864) Figs. 18-20

Tetragonopterus (Hemibrycon) polyodon Günther, 1864: 330 (original description; type locality: Guayaquil [río Pastaza basin, río Marañon drainage, upper rio Amazonas basin, Ecuador - see Remarks below]).

Hemibrycon polyodon . Eigenmann, 1909: 313 (listed, Guayaquil). - Román-Valencia et al., 2007: 184 (diagnose and redescription).

Hemibrycon coxeyi Fowler, 1943: 1-3 , fig. 1 (original description; holotype: ANSP 70155 ; type locality: Hacienda Las Mascota , mouth of the río Pastaza, drainage of the Marañon, Ecuador). [NEW SYNONYM]

Hemibrycon pautensis Román-Valencia , Ruiz-C. & Barriga, 2006: 212 (original description; type locality: río Paute en la desenbocadura del río Namangoza, cuenca del Amazonas, provincia de Morona-Santiago, Ecuador). [NEWSYNONYM]

Diagnosis. Hemibrycon polyodon is distinguished from most of its congeners by the number of branched anal-fin rays (24- 28 vs. 15-24 or 28-34, Fig. 2 ). From the species sharing similar lateral line counts, it differs from H. boquiae by the number of scale rows above and below lateral line (8 and 6 vs. 6-7 and 4-5, respectively), and by the number of predorsal scales (15-17 vs. 12-15); from H. brevispini and H. cairoense by the number of scale rows above lateral line (8 vs. 6-7); from H. dariensis , H. divisorensis , H. surinamensis and H. taeniurus by the number of lateral line scales (42-45 vs. 39-42, Fig. 3); from H. huambonicus by the number of caudal peduncle scales (16 vs. 18-20), head length (20.9-22.9 vs. 22.0-26.0% SL), and upper jaw length (43.7-45.6 vs. 45.2-52.6% HL); from H. inambari by the number of scales along anal-fin base scale sheath (14-23 vs. 6- 10); from H. jabonero by the number of caudal peduncle scales (16 vs. 14), and number of scale rows below lateral line (6 vs. 4- 5); from H. jelskii by the number of maxillary teeth (7-10 vs. 8- 17), and by the size of humeral spot (6-7 vs. 7-9 horizontal series of scales); from H. metae by the number of cusps of second tooth of premaxillary inner row teeth (5 vs. 7), caudal peduncle length (14.4-16.6 vs. 11.1-14.8% SL), and head length (20.9-22.9 vs. 22.1-25.0% SL); from H. quindos by the number of scale rows above and below of lateral line (8 and 6 vs. 6-7 and 4-5); from H. rafaelense by the number of predorsal scales (15-17 vs. 10-13), orbital diameter (29.5-34.1 vs. 36.6-43.6% HL), and interorbital width (32.1-35.3 vs. 34.7-41.5% HL); and from H. raqueliae and H. yacopiae by the number of predorsal scales (15-17 vs. 10-14), and by the number of cusps of first maxillary tooth (3 vs. 5 in H. raqueliae ). Furthermore, H. polyodon can be distinguished from H. surinamensis and H. divisorensis by the absence of a wide black asymmetrical spot covering base of caudal-fin rays, and from H. dariensis by the absence of pigment in the distal tip of rays just above and below to middle caudal-fin rays.

Description. Morphometric data for H. polyodon summarized in Table 5. Largest male 74.9 mm SL, largest female 69.5 mm SL. Body compressed and moderate elongate; greatest body

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depth at vertical through middle length of pectoral fins. Dorsal profile of head slightly convex. Dorsal body profile convex from occipital bony to base of last dorsal-fin ray; straight from this point to adipose-fin origin. Ventral profile of head nearly straight to slightly convex. Ventral body profile convex from pectoral-fin origin to pelvic-fin origin, and straight to anal-fin origin. Body profile along anal-fin base posterodorsally slanted. Caudal peduncle elongate, nearly straight to slightly concave along dorsal and ventral margins.

Snout rounded from margin of upper lip to vertical through anterior nostrils. Head small. Mouth terminal, mouth slit nearly at horizontal through middle of eye. Maxilla long and slightly curved, aligned at angle of approximately 45º to 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 3-5, tricuspid teeth with central cusp slightly longer; inner row with 4 tri- to pentacuspids 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 fully 758 A review of the Cis-Andean species of Hemibrycon toothed with 7-10 uni- to tricuspid teeth, with central cusp longer. Three anteriormost dentary teeth larger, with 5 cusps, followed by medium sized tooth with 3-5 cusps, and 7-9 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. 20 ).

Dorsal-fin rays ii,8 (n = 15); first unbranched ray approximately one-half length of second ray. Dorsal-fin origin located approximately to middle of SL and posterior to vertical through pelvic-fin origin. Profile of distal margin of dorsal fin nearly straight. Males with bony hooks in distal one-third of first to fifth branched rays. Adipose-fin located at vertical through insertion of two last anal-fin rays. Anal-fin rays iiiv,24-28 (one with 24 and one with 28, mode = 26, n = 14, Fig. 2 ). Anal-fin profile convex in males and nearly straight in females. Anal-fin origin approximately at vertical through middle dorsal-fin base. Anal-fin rays of males bearing one pair of developed bony hooks along posterolateral border of each segment of lepidotrichia, along last unbranched ray and all branched rays. Hooks usually located along posteriormost branch and distal 1 / 2 to 2 / 3 of each ray. Pectoral-fin rays i,10-12 (mode = 11, n = 15). Pectoral-fin tip reaching pelvic-fin origin in males. Males with bony hooks on distal portion of unbranched and all branched rays. Pelvic-fin rays i,6,i (n = 15). Pelvic-fin origin located 5-6 predorsal scales anterior to vertical through dorsal-fin origin. Pelvic fin of males usually bearing one developed bony hook per segment of lepidotrichia along ventromedial border of all branched rays. Caudal fin forked with 19 principal rays without bony hooks (n = 15); lobes similar in size. Caudal-fin base with few scales. Dorsal procurrent rays 12 and ventral procurrent rays 11 (n = 2).

Scales cycloid, moderately large. Lateral line complete with 42-45 (mode = 45, n = 14, Fig. 3). Scale rows between dorsalfin origin and lateral line 8 (n = 15); scale rows between lateral line and pelvic-fin origin 6 (n = 15). Predorsal scales 15-17, arranged in regular series (mode = 16, n = 13). Scales rows around caudal peduncle 16 (n = 14). Axillary scale on pelvicfin origin extends posteriorly covering 2-3 scales. Scale sheath along anal-fin base with 14-23 scales in single series, extending to base of 15 th to 24 th branched rays.

Precaudal vertebrae 18-19; caudal vertebrae 22-24; total vertebrae 40-43. Supraneurals 7-9. Gill rakers on upper limb of outer gill arch 7-8, and on lower limb 11-13 (n = 5).

Color in alcohol. The holotype is discolored, except for the middle caudal-fin rays ( Fig. 18 ). Color based on the non-type specimens. General ground body color yellowish. Dorsal portion of head and body with concentration of black chromatophores. Dorsolateral portion of head and body with scattered black chromatophores. Midlateral body silvery. One large and vertical black humeral spot, located over fourth to sixth lateral line scales and extending over 6-7 horizontal series of scales, including lateral line. Midlateral dark stripe extending from humeral region to middle caudal-fin rays, broad in caudal peduncle.Abdominal region almost devoid of black chromatophores. Dorsal, caudal, and anal fins with scattered black chromatophores. Pectoral, pelvic and adipose fins hyaline ( Fig. 19 ).

Sexual dimorphism. Males of Hemibrycon polyodon are easily recognized by the presence of bony hooks on the dorsal-, pectoral-, anal- and pelvic-fin rays. Males and females also slightly differ in pectoral- and pelvic-fin lengths ( Table 5) and in anal-fin shape, which is convex in males and nearly straight in females. Gill glands were not found on first gill arch in either males or females.

Distribution. Hemibrycon polyodon is known from the río Pastaza, río Marañon drainage, and upper ríoAmazonas basin, Ecuador ( Fig. 4 ).

Remarks of Hemibrycon polyodon . Günther (1864) described Tetragonopterus polyodon based on a single specimen from Guayaquil, Ecuador. Eigenmann (1927: 409-410) in his revision of the genus, assigned the distribution of H. polyodon as “Coastal streams of Ecuador ”, also stated that “It is more than probable that the types were shipped from Guayaquil but were collected at a considerable elevation in the interior of Ecuador or Peru ”.

Recently, Román-Valencia et al. (2007) redescribed H. polyodon based in the digital image of holotype and some additional specimens from Santiago and Morona River basins. They furnished an insufficient diagnose for the recognition of the species, and the characters described in their diagnosis

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[“ aleta dorsal con radios simples y ramificados de igual longitud, una mancha humeral estrecha y verticalmente alargada que alcanza una horizontal trazada desde el borde inferiror del opérculo ”] were not found in our analysis of the holotype and non-type specimens of H. polyodon . Also, the authors commented that the supraorbital bone is found in this species, as well as other Hemibrycon species , but this bone is absent in all species of Hemibrycon we have examined (see discussion in Bertaco et al., 2007).

Remarks of Hemibrycon coxeyi . The holotype of Hemibrycon coxeyi is badly preserved, lacking several body scales, with dorsal fin and snout broken, and body completely discolored. Only some measurements were taken, as fins length (except dorsal fin), body and caudal peduncle depth, and caudal peduncle length.All scales and fin ray counts were taken, except for the count of anal-fin scale sheath. Fowler (1943: 2) described H. coxeyi based on one of three specimens collected by Mr. W. Judson Coxey in 1931 in Ecuador. The author provided the exact locality according to Coxey trip: “All these specimens are from the basin of the Río Pastaza, in Tungurahua, where he spent some time on the river at the Hacienda Las Mascota”. Fowler recognized that H. coxeyi was nearly related to H. polyodon from the Pacific slope of Ecuador, but he was unable to identify the new species as H. polyodon based on Günther’s description. Böhlke (1958: 24-25) doubted the type locality of H. coxeyi reported by Fowler (“Hacienda Las Mascota, mouth of the Rio Pastaza, basin of the Rio Maranon, Ecuador ”) and in footnote cited a reference to the location: “Annals Entomol. Soc. America, vol. 34, no. 4, Dec. 1941, p. 848”. According to Böhlke, this reference places Hacienda Las Mascota at a point far removed from mouth of the Pastaza (01º25’S 78º11’W), a station occupied on several occasions for some length of time by Coxey.The exact location of mouth of the río Pastaza is about 04º52’S 76º21’W according to Böhlke and current maps. Latter, Géry (1962: 66) discussing about the distribution of the known forms of Hemibrycon , commented that H. coxeyi is probably a synonym of H. huambonicus , and H. polyodon comes very probably from the same area of these species.According to Lima et al. (2003) the type locality should be amended to “ Ecuador, Napo-Pastaza, Hacienda Mascota, río Topo, a tributary of río Pastaza, 01º25’S 78º11’W. The type localities of H. polyodon and H. coxeyi were inexact, but can be in some place of río Pastaza drainage, a relatively large tributary to the left margin of río Marañon, upper río Amazonas basin, in Ecuador.

A comparison of the holotypes of H. polyodon and H. coxeyi , and new specimens from río Pastaza drainage failed to reveal any differences in examined meristic and morphometric features or other characters. Hemibrycon coxeyi is, therefore, considered a junior synonym of H. polyodon , an action previously suggested by Géry (1962).

Remarks of Hemibrycon pautensis Román-Valencia , Ruiz- C. & Barriga, 2006. Hemibrycon pautensis was described by Román-Valencia et al. (2006) based on specimens collected in río Paute, a tributary of the río Santiago drainage, río Marañon drainage, Ecuador. The río Santiago is nearly located to río Pastaza, both affluents of left margin of río Marañon drainage, in Peru and Ecuador, where also occurs Hemibrycon polyodon . In the original description, one of the characters presented in the diagnosis, the presence of six to seven branched dorsal-fin rays in H. pautensis was not found in the species of Hemibrycon analyzed in this study, as well as in any other Stevardiinae (sensu Mirande, 2009, 2010). Another character used by those authors in the diagnosis of the species, the number of branched anal fin rays (27-28), can be easily found in several species of the genus that were not compared in the diagnosis of their new species. Moreover, the authors presented different values along the text and table for counts of branched rays of anal-fin (27-28 and 25-28) and dorsal-fin (7-8 and 8-9), and number of maxillary teeth (7-11 and 9-11) for that species, respectively. Furthermore, the authors referred to the presence of a supraorbital bone in H. pautensis , and other Hemibrycon species , but this bone is absent in all species of Hemibrycon examined (Bertaco et al., 2007).

Analyzing the characters presented in the diagnosis and in the description of H. pautensis it is not possible to distinguish this species from H. polyodon , also found in the río Santiago drainage according to Román-Valencia et al. (2006). Intriguing, however, the authors did not compare H. pautensis with H. polyodon in the diagnosis, but only with some of the species of the genus. Therefore, we considered H. pautensis a junior synonym of H. polyodon .

Material examined. Hemibrycon polyodon, BMNH 1858.7.25.41, holotype, female, 70.4 mm SL, Guayaquil [Ecuador]. Hemibrycon coxeyi, ANSP 70155, holotype, female (x-ray), 86.0 mm SL, Hacienda Mascota, río Topo, a tributary of the río Pastaza, drainage of the río Marañon, Napo-Pastaza, Ecuador, 01º25’S 78º11’W, Apr 1931, W. J. Coxey, JC31-MRP-4. Non -type specimens. Ecuador, río Marañon drainage : KU 19978 , 1 , 45 , 7 mm SL, río Alpayacu 1 km E Mera, Pastaza, ca. 01º27’S 78º05’W, 23 Jul 1968 . KU 19992 , 3 , 31.0- 78.2 mm SL, río Negro , tributary of río Pastaza 1 km W of río Negro Twp., Tungurahua, ca. 01º24’S 78º13’W, 26 Jul 1968 . KU 19995 , 2 , 27.7-29.3 mm SL, río Pastaza above río Negro , Tungurahua, ca. 01º24’S 78º13’W, 26 Jul 1968 . KU 20004 , 42 of 84 (2 c&s), 15.5-72.3 mm SL, N shore río Pastaza below río Negro (town), Tungurahua, ca. 01º24’S 78º13’W, 26 Jul 1968 .

Figures

Fig. 18. Hemibrycon polyodon, BMNH 1858.7.25.41, holotype, female, 70.4 mm SL, Guayaquil, Ecuador.

Fig. 19. Hemibrycon polyodon, KU 20004, male, 71.2 mm SL, río Pastaza basin, Ecuador.

Fig. 20. Hemibrycon polyodon,KU 20004,female, 52.5mm SL. Scale bar = 1 mm.

Fig. 2. Tukey box plots of number of branched anal-fin rays in Hemibrycon species. Mean represented by thick vertical bar, and 25th and 75th percetiles as lateral borders of box plots. Number in parentheses = N.

Fig. 4. Map of central and northern South America showing geographic distribution of Hemibrycon beni (1, solid hexagon), H. divisorensis (2, open triangle), H. helleri (3, ellipse), H. huambonicus (4, solid triangles), H. jelskii (5, solid dots), H. inambari (6, rectangles), H. metae (7, solid squares), H. mikrostiktos (8, open square), H. polyodon (9, inverted triangle), H. surinamensis (10, solid diamonds), H. taeniurus (11,Trinidad Island), H.tridens (12, open circle).Some symbols represent more than one lot or locality of specimens. 1-12 = type locality of each species.