Brycon polylepis Moscó Morales, 1988

Lima, Flávio C. T., 2017, A revision of the cis-andean species of the genus Brycon Müller & Troschel (Characiformes: Characidae), Zootaxa 4222 (1), pp. 1-189 : 27-33

Brycon polylepis Moscó Morales, 1988

( Figs. 16–19 )

Brycon polylepis Moscó Morales 1988: 9 –16, fig. 2 (Original description; type locality: “Río Yasa, afluente del Río Negro, estación biomédica Kasmera, Sierra de Perijá, zona de reserva de los indios Pariríes, Estado Zulia, Venezuela”); Lima, 2004: 285–287 (Rio Tocantins basin, Brazil; diagnosis in key).

Brycon sp.: Bichuette & Trajano, 2003: 1106, 1114 (São Domingos karst area, upper rio Tocantins basin, Brazil). Brycon cf. polylepis: Fernández et al., 2006: 57 (photo; upper Río Cataniapo, Rio Orinoco basin, estado Amazonas, Venezuela).

Diagnosis. Brycon polylepis can be distinguished from all remaining cis-andean Brycon species, except B. hilarii , B. orbignyanus , and B. orthotaenia , by possessing a dark caudal peduncle stripe extending onto the middle caudalfin rays. It can be distinguished from all these species by possessing narrow longitudinal stripes along the body straight, formed by pigmentation concentrated in the medio-distal portion of scales (vs. longitudinal stripes along the body wavy, formed by pigmentantion concentrated on upper and lower portions of scales), and symphyseal teeth behind the main series of dentary teeth well-developed, approximately as large as symphyseal teeth belonging to the main series situated immediately in front of it (vs. symphyseal teeth behind the main series of dentary teeth small, considerably smaller than symphyseal teeth belonging to the main series situated immediately in front of it). Additionaly, Brycon polylepis can be diagnosed from most cis-andean Brycon species by its high lateral line counts (68–94, modally 76).

Description. Morphometric data are presented in Table 3 . Middle-sized species, largest examined specimen 248.0 mm SL. Body slender. Largest body height slightly ahead of dorsal-fin origin. Dorsal body profile slightly convex from upper lip margin to vertical through anterior naris, slightly convex to straight from latter point to basis of supraoccipital process, and slightly to moderately convex from latter point to dorsal-fin origin, straight from dorsal-fin basis to adipose-fin origin. Dorsal profile of caudal peduncle slightly concave. Ventral profile slightly convex from lower lip to pelvic-fin insertion, straight to slightly convex from this point to anal-fin origin and approximately straight along anal-fin base. Ventral profile of caudal peduncle slightly concave.

Head profile slightly acute anteriorly, mouth terminal. Maxillary extending posteriorly to vertical at anterior third of pupil. Adipose eyelid well developed. Premaxillary teeth in three rows; teeth of third row largest. Six (5), 7 (14), 8 (9), or 9 (1) tricuspidate teeth in outer series. Three (20), 4 (5), or 5 (1) tricuspidate teeth in second, inner premaxillary row, plus 3 (4) or 4 (24) tricuspidate teeth between the first and third rows. Two teeth in third premaxillary row, medial teeth largest, tetracuspidate, symphyseal teeth smaller, tricuspidate. Maxillary margins approximately parallel, straight in profile. Ten to 18 maxillary teeth, slightly smaller than teeth of first premaxillary row, anterior teeth tricuspidate, posterior teeth unicuspidate. Dentary with 5(1), 6(2), 7(3), or 8(1) teeth in main series. Anterior four dentary teeth assymetrical, considerably larger and bulkier than remaining teeth, tri- to tetracuspidate, each with central cusp distinctly larger than remaining cusps. Remaining dentary teeth progressivelly smaller, tri- to unicuspidate. Inner (lingual) series consisting of a relatively large single unicuspid symphyseal tooth, approximately as large as the symphyseal dentary teeth of main series situated immediately anterior to it, plus row of 3 (1), 4(3), 5(2), or 6(1) small, unicuspidate teeth, originating on lingual crest of dentary replacement trench at level of the smaller teeth of main series.

Scales cycloid. Lateral line complete, from supracleithrum to caudal-fin base. Sixty-eight (1), 69 (1), 75 (5), 76 (8), 77 (5), 78 (1), 79 (1), 80 (1), 82 (3), 85 (1), 91 (1), or 94 (1) scales in lateral line series; laterosensory tube simple, slightly deflected downwards. Horizontal scale rows between dorsal-fin origin and lateral line 11 (7), 12 (18), 13 (3), or 14 (1). Horizontal scale rows between lateral line and pelvic-fin 7 (10), 8 (15), 9 (1), or 10 (2). Circumpeduncular scales 20 (4), 21 (10), 22 (6), 23 (5), 24 (1), or 25 (2).

Dorsal-fin rays ii, 9. Dorsal fin origin slightly ahead of middle of SL. First dorsal-fin pterygiophore inserting behind neural spine of 11th vertebra. Anal-fin rays iii (not including first, small unbranched ray only visible in the cs specimen), 25 (1), 26 (2), 27 (10), 28 (11), 29 (2), 30(2), or 31 (1). First anal-fin pterygiophore inserting behind haemal spine of 24th vertebra. Last unbranched and anterior 3–4 branched anal-fin rays longer, remaining rays progressively shorter towards anal-fin end. Anal fin displaying numerous (c. 10–30 per fin-ray main branch) small hooks on last unbranched and posterior main branch of branched rays 19–20, associated with dense, gelatinous tissue in two specimens (MBUCV-V 15094, 197.1 mm SL; CAS 68838, 190 mm SL). Generally a single, and at most three, hooks per ray segment. Sheath of scales composed of three scale rows covering basis of anal-fin rays, inferior scale row larger. Inferior scale row formed by 25–28 rectangular scales. Pectoral-fin rays i, 11 (3), 12 (21), or 13 (4). Pelvic-fin rays i,7. Branched pelvic-fin rays with small hooks (c.15–30 per branch) on distal portion of posterior ray branches in two specimens (MBUCV-V 15094, 197.1 mm SL; CAS 68838, 190.0 mm SL). Main caudal-fin rays 10/9. Caudal fin forked, lobes rounded to slightly pointed.

Four branchiostegal rays, three on anterior ceratohyal and one on posterior ceratohyal. First gill arch with 4 hypobranchial, 12 ceratobranchial, 1 on angle, 12 epibranchial, and 4 on cartilage between pharygobranchial and ceratobranchial gill rakers. Vertebrae 46 (1). Supraneurals 12 (1), middle supraneurals with a moderately developed lateral flanges.

Coloration in alcohol. Top of head, snout, supraorbital, first and sixth infraorbitals, upper portion of fifth infraorbital and opercle, and dorsal portion of body chestnut- to dark-brown. Second, third, and fourth infraorbitals, lower half of fifth infraorbital, and lower opercle two-thirds silvery. Lateral portion of body clear, with silvery and brownish hues. Dentary, maxillary, gular area, and lower portion of body clear, with a brownish hue. Dark chromatophores concentrated at lower portion of fifth infraorbital bone and middle portion of opercle forming a relatively broad, faint postorbital dark stripe in some specimens. Humeral blotch present, approximately rounded in shape, situated immediately above lateral line, its anterior margin at level of third, extending longitudinally to posterior margin of fifth to sixth lateral line scales, and vertically one and a half scales high. Specimens around 200 mm SL (e.g., MZUSP 59000, MZUSP 88325) possess longitudinal, narrow straight stripes across the body formed by pigmentation concentrated on the central-distal portion of the scales. Longitudinal stripes less conspicuous in smaller specimens. Oblique, narrow vertical stripes resulting from coalescence of dark pigmentation concentrated on the central-distal portion of scales present in some specimens (e.g., MZUSP 88325, MZUSP 56784, MBUCV-V 15094). Broad, conspicuous caudal peduncle dark stripe, approximately rectangular in profile, extending to distal portion of 5–6 medialmost caudal-fin rays. Adipose fin cream colored. Remaining fins translucent, except for dark pigmentation moderately developed in anal-fin interradial membranes in some specimens (e.g., MUSM 11077; MUSM 33345). Specimens retaining most of the original guanine pigmentation (e.g., MUSM 33345) silvery overall, with dorsal portion plumbeous-grey.

Color in life. Based on a picture of specimen (not preserved) fished at the Río Negro, a tributary of Río Casanare, Río Orinoco basin, Colombia, provided by A. Linares, and a specimen from the Río Cataniapo, upper Río Orinoco basin, depicted by Fernández et al. (2006: 57). Overall body coloration clear, with a strong silvery hue. Tof of head, snout and dorsal region grey. Upper portion of opercle with a yellow blotch. All fins pinkish, with some yellow pigmentation at their basis.

Sexual dimorphism. Two examined specimens (MBUCV-V 15094, 197.1 mm SL and CAS 68838, 190.0 mm SL) were recorded displaying fin hooks on the anal and pelvic-fins. None of these specimens was dissected to verify their sex, but Moscó Morales (1988: 20), who examined several additional specimens that were not examined in the present study, confirmed that the males possess, while the females do not, hooks in the anal- and pelvic-fins.

Variation. Two specimens collected at the Río Nanay, a black-water tributary of the Amazon River near Iquitos (INHS 44001) are distinct from the remaining examined specimens by possessing an almost straight dorsal profile (vs. slightly convex profile), a lower body depth (20.2–20.4 % SL, vs. 23.7–29.2 % SL), and a slightly distinctly shaped caudal-peduncle stripe (slightly oblique, extending into lower portion of caudal peduncle and onto its lower surface, vs. approximately straight stripe, not extending into lower portion of caudal peduncle and onto its lower surface). Additionally, these specimens possess an average high number of lateral-line scales (85–91, vs. 68–82, median 76 scales for the remaining examined specimens). However, a specimen from the upper Río Marañon in Peru (MUSM 33345) possess a lateral-line scale count even higher (94 scales) than the specimens from the Río Nanay, without sharing with them a low body depth or a straight dorsal profile. More specimens of this scarce species are necessary for a better understanding of its intraspecific variation.

Common names. Brazil, Goiás: “ piabanha ” (pers.obs.); Venezuela, Estado Zulia: “palambra”, “dientón” ( Moscó Morales, 1988: 9); Estado Amazonas: “bocón-rey”, “palambra”, “Icuä äi” (Piaroa language) ( Fernández et al., 2006: 57).

Distribution. Described originally from Río Santa Ana and Río Limón basins, Lago de Maracaibo drainage, Venezuela, and known from scattered localities in the Río Orinoco basin in Venezuela and Colombia (record based on a photograph of a specimen angled at the upper Río Negro, a tributary of Rio Casanare, itself a tributary of Rio Meta; aproximately 6°4’N, 72°9’W; A. Linares, pers. comm.), rio Tocantins basin in Brazil, and the upper Amazon basin in tributaries of Rio Madeira, Maranõn and Amazonas in Peru ( Fig. 20 ). The species is very probably widely distributed in piedmont localities across the upper Río Orinoco and Rio Amazonas basins.

Ecological notes. Most known specimens of Brycon polylepis were collected in headwater streams and small rivers possessing clear water, swift current and generally a rocky bottom ( Moscó Morales, 1988: 20; Fernández et al., 2006: 57; pers. obs.). Specimens MZUSP 18142 were collected in a rocky pool at the rapids of Jatobal, a former extensive rapid area of the rio Tocantins now submerged under the Tucuruí dam. Curiously, as reported by Bichuette & Trajano (2003; as Brycon sp.), a small population of the species was recorded as living for several years in a cave stream at the São Domingos karst area in the upper rio Tocantins basin in Brazil; these specimens were recorded feeding cave crickets accidentally fallen in the water (pers. obs.; E. Trajano, pers. comm..). Streams in the karst zone of São Domingos run across the limestone outcrops of the Bambuí formation, heading towards the rio Paranã, one of the upper tributaries of the rio Tocantins (see Bichuette & Trajano, 2003, fig. 1), and Brycon polylepis was recorded from both sinkhole and resurgence areas in these streams (specimens MZUSP 59000, MZUSP 88325, and MZUSP 88326). Moscó-Morales (1988: 20) reported leaves, trichopteran cases, fruits, seeds, and insect remains in stomach contents he examined. Fernández et al. (2006: 57) reported, without further details, that the reproduction of the species at the Río Cataniapo had it onset during the beginning of the rainy season.

Remarks. Comparisons between the single examined paratype of Brycon polylepis from the Lake Maracaibo basin and specimens from the upper Amazon basin in Peru, rio Tocantins basin in Brazil, and Río Orinoco basin in Venezuela did not revealed any distinguishing characters between the respectively trans- and cis-andean populations of Brycon polylepis , and these specimens are accordingly referred to a single species. See the section “Biogeography”, below.

Material examined. Type material: MBUCV-V 15094 (1 of 2, 197.1 mm SL): Venezuela, Estado Zulia, Río Yasa, tributary of Río Negro (tributary of Rio Santa Ana ), Estacion Biologica de Kasmera , Sierra de Perijá , c. 9°57’N, 72°43’W; J. Moscó Morales et al., 20 Sept 1985. Paratype of Brycon polylepis Moscó Morales, 1988 .

Non types: Brasil, rio Tocantins basin , Pará: MZUSP 56784 (1, 132.2 mm SL): Parauapebas, igarapé Salobo (tributary of rio Itacaiúnas ), 5°46'45''S, 50°32'13''W; P.S. Pompeu, Nov 1997. ZUEC 7065 (1, 121.7 mm SL): Parauapebas, igarapé Salobo (trib. rio Itacaiúnas ), 5°49’33’’S, 50°29’25’’W; T. Giarizzo, 15 Dec 2009 . ZUEC 7064 (1, 105.4 mm SL): Parauapebas, igarapé Mirim (trib. rio Itacaiúnas ), 5°45’36’’S, 50°30’59’’W; T. Giarizzo, 15 Sept 2009 . MZUSP 18142 (1, 106.9 mm SL; 1, 104.4 mm SL, cs), rio Tocantins, lagoon at Jatobal , 4°32’S, 49°28’W; EPA, 16 Sept 1970 . INPA 16391 (1, 100.6 mm SL), igarapé Valentim, tributary of rio Tocantins, Tucuruí-Marabá road, km 130; G.M. Santos, 6 July 1982 . Goiás: MCP 16008 (3, 113.8– 122.4 mm SL), Niquelândia, Ribeirão Arara, 500 m from its mouth in the rio Maranhão at Rosariana ; 14°01'S 48°25'W; R.E. Reis et al., 14 July 1992 . MZUSP 59000 (1, 202.7 mm SL), São Domingos, entrance of Lapa da Bezerra, Terra Ronca State Park , 13°32'43'' S, 46°22'35'' W ; A. Akama, 24 June 1999. MZUSP 88325 (1, 189.4 mm SL), São Domingos , Rio da Lapa at its resurgence, Caverna Terra Ronca, Terra Ronca State Park ; M.E. Bichuette & R. Santos, 14 Sept 1999 . MZUSP 88326 (2, 200.9– 201.3 mm SL), São Domingos, Rio da Lapa, at entrance of Caverna Terra Ronca, Terra Ronca State Park , 13°44’00’S, 46°21’30’’W; M.E. Bichuette & R. Santos, 14 Sept 1999 . MNRJ 13069 (4, 109.2– 125.2 mm SL), Formosa, rio Água Quente (tributary of rio Paranã), at the crossing of the Formosa-Itiquira- Flores de Goiás road, 74 km from Formosa, 14°58'23''S, 47°28'36''W; L.E.M. Cardoso, 4 Sept 1982 . IBGE uncat. (1, 107.0 mm SL): São João da Aliança, stream trib. rio Paranã, fazenda Farias , 14°31'18'’S, 47°10'36'’W; M.C.L. Ribeiro et al., 14 June 1990 . MZUSP 70413 (2, 192.2– 203.9 mm SL), rio Tocantins, downstream UHE Serra da Mesa , 13°49'54.8''S, 48°17'44.2''W; D.F. Moraes & D . A. Halboth, 4–5 Feb1997. MZUSP 70414 (1, 120.6 mm SL), rio Tocantizinho, Serra da Mesa dam, 13°57'10''S, 48°19'33''W; D.F. Moraes & D . A. Halboth, 4 Dec 1997 . MZUSP 70419 (1, 103.7 mm SL), rio Maranhão, near rio do Peixe mouth, 14°14'54.9 '' S, 48°55'39.7''W; D.F. Moraes & F.P. Matos, 12 Feb 1997 . MZUSP 71671 (1, 90.2 mm SL), córrego do Cavalo, tributary of rio Tocantins, above Serra da Mesa dam, 14°31'16'’S, 48°56'6'’W; J.C . Miranda et al., 11 Feb1997. IBGE uncat. (1, 200.0 mm SL): Padre Bernardo , Rio do Sal, trib. rio Maranhão, 15°20’20’’S, 48°3’5’’W; M.C.L. Ribeiro et al., 6 Aug 1998. CAS 68838 (1, 190 mm SL) ; CAS 68834 (1, 200 mm SL): upper Rio Maranhão at “ Mosondo ” (not located), into rio Tocantins; C. Ternetz, 2–4 Oct 1923 . CAS 68823 (1, 208 mm SL), " Tirap-lanya " (not located), rio Maranhão, into rio Tocantins; C. Ternetz, 2 Oct 1923 .

Peru: INHS 44001 (2, 109.7– 124.1 mm SL), Depto. Loreto , Río Nanay, Pampa Chica, 4.54 km W center of Iquitos , 3°45'08.8''S 73°17'00.1''W; M.H. Sabaj & J.W. Armbruster, 22 July 1997. MUSM 11077 (1, 206.0 mm SL): Depto . Puno, Sandi, Zona Reservada Tambopata/Candamo , Río Candamo (tributary of Rio Tambopata), quebrada Ebebahuaeji , c. 13°24'S, 69°35'W; F. Chang, 31 March 1997. MUSM 33345 (1, 248.0 mm SL): Depto . San Martin, Prov. M. Cáceres, Huicungo , Río Abiseo (tributary of Rio Huallaga) , Río Abiseo National Park, 7°26'56''S 76°53'43''W; H. Ortega , A. Díaz & P. Zuñiga, 20 May 2008. MUSM 43197 (1, 123.3 mm SL): Depto . Ucayali, Coronel Portillo , Río Shesha (trib. Río Ucayali), 8°11’17’’S, 73°56’38’’W; V. Meza et al., 17 Oct 2011.

Venezuela, Río Orinoco basin: ANSP 159717 (1, 93.7 mm SL), Bolivar, caño 15.1 km E of Río Parguaza, ferry crossing on Caicara-Puerto Ayacucho hwy, 6°26’28’’N, 67°9’24’’W; B. Chernoff et al., 28 Nov 1985.

Figures

FIGURE 16. Brycon polylepis, paratype, MBUCV-V 15094, 197.1 mm SL: Venezuela, Zulia, Río Yasa.

FIGURE 17. Brycon polylepis, MZUSP 70413, 203.9 mm SL: Brazil, Goiás, rio Tocantins basin.

FIGURE 18. Brycon polylepis, MCP 16008, 122.4 mm SL: Brazil, Goiás, rio Tocantins basin.

FIGURE 19. Brycon polylepis, INHS 44001, 124.1 mm SL: Peru, Loreto, Río Nanay.

FIGURE 20. Map of northern South America showing known localities of Brycon polylepis (red dots) and B. coquenani (black dot).

Tables

TABLE 3. Morphometric data of Brycon polylepis (A: paratype, MBUCV-V 15094).

	A	n	Range	Mean
Standard length (SL)	197.1	29	90.2–248.0	-
Percentages of standard length
Depth at dorsal-fin origin	26.1	27	20.2–29.2	25.4
Snout to dorsal-fin origin	51.8	29	47.5–51.6	49.5
Dorsal-fin base length	10.6	29	9.6–11.6	10.8
Posterior terminus of dorsal fin to adipose fin	24.0	29	22.5–27.1	24.9
Posterior terminus of dorsal fin to hypural joint	37.7	29	35.6–43.8	38.6
Snout to pelvic-fin insertion	43.2	28	40.8–46.8	44.0
Snout to anal-fin origin	58.5	29	56.9–65.1	60.6
Anal-fin base length	27.2	29	24.6–29.1	26.5
Caudal peduncle length	16.3	29	12.9–17.6	15.8
Dorsal-fin height	20.0	29	16.4–21.6	18.8
Pectoral-fin length	16.3	29	15.4–20.2	17.7
Pelvic-fin length	16.6	29	13.1–16.7	15.1
Caudal peduncle depth	9.2	29	7.7–9.5	8.3
Head length	23.2	29	20.3–25.6	22.8
Percentages of head length
Head height	71.6	29	65.8–82.5	74.6
Snout length	28.4	29	26.7–32.5	28.2
Upper jaw length	42.2	29	37.5–43.8	40.7
Horizontal eye diameter	22.8	29	20.8–30.7	26.3
Post-orbital length	46.2	29	40.4–50.5	45.4
Least interorbital width	33.9	29	29.5–38.6	34.1