Brycon vonoi, Lima, Flávio C. T., 2017

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 : 63-66

Brycon vonoi new species

( Figs. 36–37 )

Diagnosis. Brycon vonoi can be diagnosed from all remaining cis-andean Brycon species, with the exception of B. stolzmanni , B. coxeyi , B. coquenani , B. vermelha , B. insignis , B. howesi , B. dulcis , B. ferox , B. opalinus , and B. nattereri by possessing a color pattern consisting in a humeral blotch and a caudal peduncle blotch, without body stripes or other obvious color markings on caudal and anal-fins (vs. body stripes and caudal/anal fin color markings present; see Fig. 5 ). Brycon vonoi can be distinguished from B. ferox , B. vermelha , B. insignis , B. howesi , B. coquenani , and B. dulcis by possessing a slightly acute head profile (vs. a distinctly acute head profile). Brycon vonoi can be distinguished from Brycon stolzmanni and B. coxeyi by the absence of a patch of dark pigmentation on the opercle (vs. dark patch of pigmentation present on opercle). Brycon vonoi can be additionally distinguished from B. insignis , B. howesi , B. coquenani , and B. vermelha by possessing a fifth infraorbital bone about as wide as high (vs. fifth infraorbital bone wider than high; see Fig. 6 ). Brycon vonoi can be additionally distinguished from B. dulcis by possessing a clear overall color pattern (vs. darkened overall body color). Brycon vonoi can be distinguished from B. nattereri by possessing lateral line tubules mostly simple (vs. tubules with 2–5 branches), caudal peduncle blotch not extending into middle caudal-fin rays (vs. caudal peduncle blotch extending into middle caudal-fin rays), and roughly V-shaped blotch on outer caudal-fin rays present (vs. outer caudal-fin rays clear, without dark pigmentantion). Brycon vonoi can be distinguished from B. opalinus by presenting an acute, pointed snout (vs. obtuse, rounded snout) and a longer upper jaw length (45.1–51.4 % of HL, mean 49.5, vs. 38.7–48.3 of HL, mean 42.9).

Description. Morphometric data are presented in Table 11 . Middle-sized species, largest examined specimen 278.0 mm SL. Body moderately 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 concave from latter point to basis of supraoccipital process, moderately convex from latter point to dorsal-fin origin, straight along dorsal-fin basis, and straight to slightly convex 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. Jaws isognathous to slightly anisognathous, premaxillary projecting slightly relative to dentary in some specimens, leaving outer row of premaxillary teeth exposed when mouth is closed. Maxillary long, extending posteriorly to anterior third to middle of pupil. Adipose eyelid well developed. Premaxillary teeth in three rows; teeth of third row largest. Five (1), 6 (8), 7 (7), 8 (2), 9 (6), 10 (1), or 11 (2) tricuspidate teeth in outer series. Three (3), 4 (11), 5 (10), or 6 (2) tri- to tetracuspidate teeth in second, inner premaxillary row, plus 2 (2), 3 (12) or 4 (12) tricuspidate teeth between the first and third rows. Two teeth in third premaxillary row, medial teeth largest, symphyseal teeth smaller, slightly tilted towards each other, both pentacuspidate. Maxillary with distal portion distinctly expanded and rounded in profile. Seventeen to 27 maxillary teeth, slightly smaller than teeth of first premaxillary row, anterior teeth tricuspidate, posterior teeth unicuspidate. Dentary with 9(2), 10 (2), 11 (3), 12 (1), or 14 (2) teeth in main series. Anterior four dentary teeth assymetrical, considerably larger and bulkier than remaining teeth, penta- to hexacuspidate, each with central cusp distinctly larger than remaining cusps. Remaining dentary teeth progressivelly smaller, tetra-, tri- to unicuspidate. Inner (lingual) series consisting of a small, single unicuspid symphyseal tooth, situated immediately posterior to symphyseal dentary teeth of main series, plus row of 25–31 small, unicuspidate teeth, originating on lingual crest of dentary replacement trench at the level of third main series dentary teeth.

Scales cycloid. Lateral line complete, from supracleithrum to caudal-fin base. Forty-five (3), 46 (4), 47 (13), 48 (6), or 49 (2) scales in lateral line series. Laterosensory tube generally simple, deflected upwards in the first 5–6 scales, downwards in the remaining lateral-line scales. Larger specimens (> 230 mm SL) with with tubules bifurcated in some scales. Horizontal scale rows between dorsal-fin origin and lateral line 6 (1), 7 (16) or 8 (11). Horizontal scale rows between lateral line and pelvic-fin 4 (22) or 5 (6). Circumpeduncular scales 14 (1), 15 (2), 16 (14), 17 (9), or 19 (1).

Dorsal-fin rays ii, 9. Dorsal fin origin slightly ahead of middle of SL. First dorsal-fin pterygiophore inserting behind neural spine of 13th (1) or 14th (1) vertebra. Anal-fin rays iii (not including first, small unbranched ray only visible in the cs specimen), 20(1), 21 (7), 22 (12), 23 (4), or 25 (3). First anal-fin pterygiophore inserting behind haemal spine of 23th (2) vertebra. Last unbranched and anterior 4–5 branched anal-fin rays longer, remaining rays progressively shorter towards anal-fin end. Anal fin displaying numerous (c. 25–30 per fin-ray main branch) middle-sized hooks on last unbranched and posterior main branch of branched rays 11–23, associated with dense, gelatinous tissue in 7 specimens (MZUSP 58297, 1, 210.6 mm SL; MZUSP 93815, 2, 195.2– 192.3 mm SL; ZUEC 10746, 1, 189.6 mm SL; MCP 49962, 1, 194.1 mm SL; MCNIP 1595, 1, 193.4 mm SL; MCNIP 1596, 1, 182.6 mm SL), one of which (MZUSP 58297) a female (see “Sexual dimorphism”, below). A single hook per ray segment. Sheath of scales covering basis of anal-fin rays composed of two scale rows, lower scale row formed by 20–23 rectangular scales. Pectoral-fin rays i, 10 (2), 11 (8), or 12 (17). Pelvic-fin rays typically i, 7, one specimen i, 8. Main caudal-fin rays 10/9. Caudal fin forked, lobes rounded.

Four branchiostegal rays, three on anterior ceratohyal and one on posterior ceratohyal. First branchial arch with 11 (1), 13 (1), or 16 (1) lower, 1 at angle, and 11 (1), 12 (1), or 13 (1) upper gill rakers. Vertebrae 43 (2). Supraneurals 10 (1) or 11 (1).

Coloration in alcohol. Overall body coloration clear. Top of head, snout, supraorbital, sixth infraorbital, and dorsal portion of body grayish to brownish. Second, third, fourth, and fifth infraorbitals, and opercle silvery. Dentary, maxillary, gular area and lower portion of body light brown. Lateral portion of body clear, with a silvery hue. Humeral blotch present, moderately conspicuous, approximately rounded in shape, situated immediately above lateral line, its anterior margin at level of second, extending longitudinally to posterior margin of fourth lateral line scales, and vertically less than one scale high. Large, little to moderately conspicuous, oval-shaped caudal peduncle blotch, extending along 5–6 last lateral-line scales. Rayed fins clear, with dark chromatophores scattered over the interradial membranes. Caudal-fin with a poorly discernible, roughly V-shaped blotch, formed by dark pigmentantion situated on outer caudal-fin rays. Adipose fin light-grey to light-brown.

Color in life. The holotype (MZUSP 58297), a year and a half after being collected (September 1999), still retained orange blotches at the centre of the scales from the two horizontal scale rows situated below lateral line scale row, anterior to insertion of pelvic fins.

Sexual dimorphism. Seven specimens (MZUSP 58297, 1, 210.6 mm SL; MZUSP 93815, 2, 195.2– 192.3 mm SL; ZUEC 10746, 1, 189.6 mm SL; MCP 49962, 1, 194.1 mm SL; MCNIP 1595, 1, 193.4 mm SL; MCNIP 1596, 1, 182.6 mm SL) displayed anal-fin hooks. One of these specimens (MZUSP 93815, 192.3 mm SL) was dissected and is a male, with well-developed testicles. On other hand, the specimen MZUSP 58297 is a female, presenting oocytes at the urogenital opening. Another obviously mature female specimen, presenting oocytes at the urogenital opening (MZUSP 93815, 278.0 mm SL) does not present fin hooks. Fin hooks are generally regarded as being a dimorphic feature, present only in males ( Malabarba & Weitzman, 2003). In fact, data for other Brycon species examined in the present study confirm this view. Consequently, the occurrence of anal-fin hooks in the mature female specimen MZUSP 58297 should be considered an abnormal condition.

Etymology. The specific name honors our dear colleague and friend Volney Vono (1961–2011), who was the first ichthyologist to collect the new species and who brought it to the attention of the author.

Common names. “ Piabanha ” (V. Vono, O.T. Oyakawa, pers. comm.).

Distribution. Only known, and apparently endemic from the rio Pardo basin, a small coastal drainage situated at Minas Gerais and Bahia states, immediately north from the rio Jequitinhonha basin, eastern Brazil ( Fig. 32 ).

Conservation. The original Atlantic forest which formerly covered most of the rio Pardo basin was historically largely replaced by pastureland and crops. There is a hydroelectric dam (Machado Mineiro dam) build in the middle rio Pardo that very likely has affected adversely the species. Unfortunately, more hydroelectric dams are being planned for the rio Pardo basin. Brycon vonoi is being artificially bred at a fish hatchery situated at the Machado Mineiro hydroelectric dam. Probably, as almost all remaining eastern brazilian Brycon species, the species is threatened with extinction, though it is necessary to obtain additional field data to ascertain its current conservation status.

Remarks. There is an old lot (MCZ 2416) said to have been collected at the “rio Una” by “ A. de Lacerda. Antônio de Lacerda was an amateur brazilian naturalist resident at Salvador, Bahia, who assisted N. Dexter and S.V.R. Thayer from the Thayer Expedition during their stay at that city ( Dick, 1977: 6; Agassiz & Agassiz, 1975: 93). The lot MCZ 2416 was collected previously (1864) to the Thayer Expedition, presumably at the rio Una which lies at the city of Valença, where Lacerda’s family owned a cottom mill industry. This locality lies considerably to the north (~ 220 km) from the mouth of the rio Pardo, the type-locality of Brycon vonoi . These specimens are similar to Brycon vonoi and are herein provisionally considered to be conspecific to this species. More collecting in the coastal rivers of central and northern Bahia are, however, necessary to understand the taxonomical status of Brycon populations in the area (see also “Remarks” of Brycon devillei and B. opalinus ).

Material examined. Holotype: MZUSP 58297 (1, 210.6 mm SL): Brazil, Minas Gerais, Taiobeiras, rio Pardo, Fazenda Tabatinga , c. 15°43’S 42°14’W; V. Vono, 17 Feb 1998.

Paratypes. Brazil, Minas Gerais, rio Pardo basin. MZUSP 104020 (1, 151.0 mm SL): same data as holotype . MZUSP 83434 (3, 149.2–232.0 mm SL): Berizal, rio Pardo , c. 15°35'S, 41°44'W; B.P. Nogueira & M.F.G. Brito, 23 Jun 2000 . MCNIP 1595 (2, 178.6– 193.4 mm SL); ZUEC 10746 (2, 166.0– 189.6 mm SL); ANSP 200241 (1, 165.0 mm SL); MCP 49962 (1, 194.1 mm SL); MNRJ 45957 (1, 164.0 mm SL): Águas Vemelhas, rio Pardo, immediatelly below Machado Mineiro hydroeletric dam, 15°31'25''S, 41°30'26''W; T.C. Pessali et al., 15 Feb 2015 . MZUSP 93815 (17, 82.1–278.0 mm SL, 2 cs, 84.9–92.8 mm SL): Águas Vermelhas, CEMIG fish hatchery (stocked from specimens collected at the rio Pardo), UHE Machado Mineiro , 15°31’19’’S, 41°30’18’’W; O.T. Oyakawa, J.L. Birindelli & L.M. Sousa, 16 Apr 2007 . MZUSP 108439 (1, 124.6 mm SL): Ninheira, Rio Pardo, UHE Machado Mineiro , 15°31’S, 41°31’W; W . A. Meireles, March 2011. MCNIP 1596 (11, 103.0– 182.6 mm SL) ; ZUEC 10747 (4, 105.1– 113.7 mm SL): Ninheira, CEMIG fish hatchery (stocked from specimens collected at the rio Pardo), UHE Machado Mineiro , 15°31’19’’S, 41°30’18’’W; T.C. Pessali et al., 14 Feb 2015.

Additional material (not typical). UFMG uncat. (1, 221.6 mm SL): same data as holotype. MCZ 2416 (2, 200.0– 260.5 mm SL): Bahia, “Rio Una” [c. 13°22’S, 39°5’W; see Remarks, above]; A. de Lacerda, 18 March 1864.

Figures

FIGURE 5. Diagrammatic representation of the patterns of dark colour markings found among cis-andean Brycon species, represented by selected species. A. Brycon stolzmanni. B. Brycon coxeyi. C. Brycon insignis. D. Brycon nattereri. E. Brycon hilarii. F. Brycon whitei. G. Brycon amazonicus. H. Brycon gouldingi. I. Brycon melanopterus. J-L. Brycon falcatus.

FIGURE 6. Diagrammatic representation of the head profile, maxillary and infraorbitals showing the distinct morphologies found among cis-andean Brycon species, represented by selected species. A. Brycon amazonicus, MZUSP 3815, 152.3 mm SL. B. Brycon insignis, MCZ 21112, 232.2 mm SL. C. Brycon dulcis, MZUSP 1531, 146.6 mm SL. D. Brycon falcatus, MZUSP 3845, 195.1 mm SL. E. Brycon opalinus, MCZ 21123, 210.5 mm SL. F. Brycon orbignyanus, MZUSP 3900, 108.9 mm HL. G. Brycon ferox, MCZ 60934, 310.3 mm SL. H. Brycon orthotaenia, MZUSP 2007, 188.7 mm SL. I. Brycon polylepis, MZUSP 70413, 203.9 mm SL. J. Brycon stolzmanni, UMMZ 185306, 120.0 mm SL.

FIGURE 32. Map of eastern Brazil, showing known localities of Brycon dulcis (red dots; red star indicates type locality), B. ferox (black dots), and B. vonoi (purple dots; purple star indicates type locality).

FIGURE 36. Brycon vonoi, new species, holotype, MZUSP 58297, 210.6 mm SL: Brazil, Minas Gerais, rio Pardo.

FIGURE 37. Brycon vonoi, new species, paratype, MZUSP 93815, 103.8 mm SL: Brazil, Minas Gerais, rio Pardo.

Tables

TABLE 11. Morphometric data of Brycon vonoi (A: holotype, MZUSP 58297).

	A	n	Range	Mean
Standard length (SL)	210.6	17	96.3–278.0	-
Percentages of standard length
Depth at dorsal-fin origin	30.9	26	25.4–31.3	28.4
Snout to dorsal-fin origin	52.0	27	49.7–55.0	52.5
Dorsal-fin base length	10.2	27	10.2–14.0	12.1
Posterior terminus of dorsal fin to adipose fin	24.4	27	20.9–24.8	22.7
Posterior terminus of dorsal fin to hypural joint	33.5	27	33.2–39.6	37.3
Snout to pelvic-fin insertion	50.6	27	47.4–52.1	49.9
Snout to anal-fin origin	71.1	26	65.8–74.3	66.7
Anal-fin base length	21.3	26	21.3–26.2	23.9
Caudal peduncle length	12.1	27	11.1–14.9	13.8
Dorsal-fin height	17.5	27	17.4–21.8	19.5
Pectoral-fin length	18.5	27	16.8–21.4	19.1
Pelvic-fin length	15.0	27	13.9–17.1	15.4
Caudal peduncle depth	9.3	27	8.0–12.4	8.8
Head length	24.3	27	22.9–30.3	26.0
Percentages of head length
Head height	80.3	27	68.3–87.8	78.8
Snout length	30.3	27	27.5–32.8	30.5
Upper jaw length	50.4	27	43.9–51.4	49.0
Horizontal eye diameter	25.2	27	22.7–28.9	26.2
Post-orbital length	45.1	27	44.8–49.4	47.0
Least interorbital width	38.5	27	32.7–44.3	38.6