Brycon opalinus ( Cuvier, 1819 )

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 : 67-74

Brycon opalinus ( Cuvier, 1819)

( Figs. 38–42 )

Chalceus opalinus Cuvier, 1819: 351 –352, pl. 26 (fig. 1) (Type locality “Brésil”, restricted by Eigenmann, 1921: 294 –295 to “Rio de Janeiro”); Valenciennes, in Cuvier & Valenciennes, 1850: 244 –246 (part; Rio de Janeiro); Eigenmann, 1921: 294 – 295 (correction of type locality).

Brycon bahiensis Günther, 1864: 334 (Type locality “ Bahia”); Howes, 1982: 11 (holotype; also material from Rio de Janeiro, Porto Real).

Brycon reinhardti (not Lütken): Steindachner, 1877: 585 –587, pl. 3, figs.3, 3a (“Rio Parahyba und Rio doce”...”Campos und Juiz de Fora”).

Brycon pirapitinga: Magalhães, 1931: 168 (“Proximo de S. Luiz do Parahytinga, entre Ubatuba e Taubaté... riosinho...”).

Brycon reinhardtii (sic) (not Lütken): Travassos & Silva Santos, 1955: 309, fig. 1e,f; plate III, fig. 2 (comparison with Brycon avus ).

Brycon opalinus: Géry & Mahnert, 1992: 812 –814 (part; holotype); Hilsdorf et al., 2002: 81 –91 (mitochondrial DNA, genetic structure; upper and middle rio Paraíba basin); Barroso et al., 2005: 51 –65 (microsatellite loci, genetic structure; upper and middle rio Paraíba basin); Vieira et al., 2005: 80 –84, fig. 2c (Upper rio Doce basin, Serra do Cipó National Park); Gomiero et al., 2006: unnumbered (predation on terrestrial vertebrates; upper rio Paraibuna basin); Menezes et al., 2007: 111 (photograph; distribution, ecology, conservation status); Gomiero & Braga, 2007a: 541 –549 (fecundity, breeding seasons, type of spawning; upper rio Paraibuna basin); Gomiero & Braga, 2007b: 727 –733 (gonadossomatic index, upper rio Paraibuna basin); Gomiero et al., 2007: 21–26 (growth, aging, upper rio Paraibuna basin); Gomiero et al., 2008: 321 –328 (diet, upper rio Paraibuna basin); Travenzoli et al., 2015: 6, 8–11, 13–14 (Rio Santo Antônio basin, Minas Gerais; cytogenetics, phylogenetics relationships, molecular taxonomy).

[not Bizerril & Primo, 2001; Bejarano et al., 2003: 362, 367; Blanco-Parra & Bejarano-Rodríguez, 2006: 856; Maldonado- Ocampo et al., 2008: 175].

Brycon cf. reinhardti (not Lütken): Narahara, 1993: 5–6 (gonadal development, maturation in captivity); Almeida-Toledo et al., 1996: 36 –37 (karyotype).

Brycon cf. opalinus: Sabino & Sazima, 1999: 312 (diet).

Brycon sp.: Bizerril & Primo, 2001: 28, 54, 231, 243, 259 (common name; rio Paraíba do Sul, rio Pomba; commercial value).

Diagnosis: Brycon opalinus 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. vonoi , 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 opalinus can be distinguished from Brycon ferox , B. vermelha , B. insignis , B. howesi , B. coquenani , and B. dulcis by possessing a rounded, obtuse head profile (vs. a distinctly acute head profile). Brycon opalinus 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 opalinus 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 opalinus can be distinguished from B. nattereri by possessing lateral line tubules mostly simple (vs. tubules with 2–5 branches), and caudal peduncle blotch not extending into middle caudal-fin rays (vs. caudal peduncle blotch extending into middle caual-fin rays). Brycon opalinus can be distinguished from B. vonoi by presenting an obtuse, rounded snout (vs. acute, pointed snout) and a shorter upper jaw length (38.7–48.3 % of HL, mean 42.9, vs. 45.1–51.4 of HL, mean 49.5).

Description. Morphometric data are presented in Table 12 . Middle-sized species, largest examined specimen 278.0 mm SL. Body slender to 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 to slightly convex 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 moderately long, extending posteriorly to anterior margin to anterior third of pupil. Adipose eyelid well developed. Premaxillary teeth in three rows; teeth of third row largest. Five (3), 6 (17), 7 (32), 8 (23), 9 (11), or 10 (1) tricuspidate teeth in outer series. Three (24), 4 (53), or 5 (7) tri- to tetracuspidate teeth in second, inner premaxillary row, plus 2 (16), 3 (53), or 4 (17) 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. Ten to 22 maxillary teeth, slightly smaller than teeth of first premaxillary row, anterior teeth tricuspidate, posterior teeth unicuspidate. Dentary with seven (3), 8 (12), 9 (20), 10 (15), 11 (9), 12 (4), or 13 (2) teeth in main series. Anterior four dentary teeth assymetrical, considerably larger and bulkier than remaining teeth, pentacuspidate, 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 10–16 small, unicuspidate teeth, originating on lingual crest of dentary replacement trench at the level of fourth to fifth main series dentary teeth.

Scales cycloid. Lateral line complete, from supracleithrum to caudal-fin base. Forty-two (1), 44 (1), 45 (2), 46 (9), 47 (3), 48 (22), 49 (15), 50 (15), 51 (5), 52 (9), 53 (3), 54 (2), 57 (1), 58 (1), or 59 (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. Some large specimens (> 230 mm SL) with tubules bifurcated in some scales. Horizontal scale rows between dorsal-fin origin and lateral line seven (3), 8 (56), 9 (30), or 10 (4). Horizontal scale rows between lateral line and pelvic-fin 4 (55), 5 (36), or 6 (1). Circumpeduncular scales 14 (1), 15 (14), 16 (43), 17 (19), 18 (12), or 19 (4)

Dorsal-fin rays typically ii, 9, two specimens ii,10. Dorsal fin origin at middle of SL. First dorsal-fin pterygiophore inserting behind neural spine of 14 th (1) or 15th (3) vertebrae. Anal-fin rays iii (not including first, small unbranched ray only visible in the cs specimen), 17 (2), 18 (7), 19 (24), 20 (39), 21 (18), 22 (10), or 23 (2). First anal-fin pterygiophore inserting behind haemal spine of 25th (2), 26th (1), or 28th (1) vertebrae. Last unbranched and anterior 4–5 branched anal-fin rays longer, remaining rays progressively shorter towards anal-fin end. Anal fin displaying numerous (c. 15–22 per fin-ray main branch) small hooks on last unbranched and posterior main branch of branched rays 16–22, associated with dense, gelatinous tissue in two specimens (MZUSP 50805, 224.6 mm SL; MZUSP 59280, 215.5 mm SL). 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 13–20 rectangular scales. Pectoral-fin rays i, 11 (10), 12 (38), 13 (43), or 14 (2). Pelvic-fin rays typically i, 7, two specimens i, 6. One specimen (MZUSP 50805, 224.6 mm SL) with minute hooks on distal portion of posterior branch of branched pelvic-fin rays. 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 10 (6), 11 (10), 12 (20), 13 (19), or 14 (3) lower, 1 at angle, and 8 (1), 9 (16), 10 (21), 11 (15), or 12 (3) upper gill rakers. Vertebrae 43 (1), 45 (1), 46 (2), or 47 (2). Supraneurals 10 (2), 11 (1), or 12 (1).

Coloration in alcohol. Overall body coloration brown. Top of head, snout, supraorbital, fifth and sixth infraorbitals, and dorsal portion of body light- to dark-brown. Second, third, fourth, and fifth infraorbitals, and opercle light-brown, silvery in specimens retaining guanine. Dentary, maxillary, gular area and lower portion of body light brown. Lateral portion of body light-brown, with a silvery hue in specimens retaining guanine. Humeral blotch present, relatively conspicuous in juveniles but little conspicuous in adult specimens, 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 one and half scales high. Large, little conspicuous, oval-shaped caudal peduncle blotch, extending along 6–7 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 in some specimens. Adipose fin light-grey to light-brown. Specimens from rio Santo Antônio basin in upper rio Doce drainage with overall body color, including fins, darkened, possibly a result of the dark waters of that river system.

Color in life. Description based on pictures of unpreserved specimens from a cultivated stock kept at the CESP-Paraibuna fish hatchery and in specimens collected at the rio Paraibuna (MZUSP 51538). Dorsal area, top of head and snout darkened. Infraorbitals and opercular bones silvery, with a diffuse dark pigmentantion. Lateral portion of body clear, with a silvery hue. Conspicuous dark peduncular blotch. Pectorals, pelvics, anal and caudal fins darkened.

Sexual dimorphism. Two specimens (MZUSP 50805, 224.6 mm SL; MZUSP 59280, 215.5 mm SL) with small hooks present on posterior branch of branched anal- and (MZUSP 50805 only) pelvic-fin rays. Both specimens were dissected and proved to be mature males, with very well-developed testes. An obviously reproductive female specimen (MZUSP 59282, 249.5 mm SL), with oocytes on the urogenital opening, lacks fin hooks.

Common names. “Pirapitinga-do-sul”; “ pirapitinga ”; “pipitinga” (MG); “parpitinga” (SP).

Distribution. Restricted to headwater tributaries from the rio Paraíba do Sul and rio Doce basins, eastern Brazil ( Fig. 43 ). A old record for the lower rio Doce basin in Espírito Santo state (MCZ 21104) is here considered doubtful in view of the known preference of the species for headwater areas. See the item “Remarks”, below, for an account on the locality “ Bahia ” (type-locality of the holotype of Brycon bahiensis ).

Variation. Specimens herein identified as Brycon opalinus generally agree in most morphometric and meristic characters. There is, however, slight morphological variation between different populations of the species. Specimens from the upper rio Paraibuna and rio Itaguaçaba at the upper rio Paraíba do Sul basin in São Paulo state and from rio Preto at the middle rio Paraíba do Sul basin in Rio de Janeiro / Minas Gerais states present a relatively lower body depth (21.3–29.8 % of SL) when compared with specimens from the rio do Peixe in the middle rio Paraíba do Sul basin in Minas Gerais (27.5–32.8 % of SL) and from specimens from the rio Santo Antônio basin (upper rio Doce drainage) in Minas Gerais (26.3–30.7 % of SL). The single cleared and stained Brycon opalinus from the rio Doce basin presented a lower total vertebral count compared with the four cleared and stained specimens from the rio Paraíba do Sul basin (43, vs. 45–47, respectively). Also, specimens from the upper rio Doce basin basin are generally darker than specimens from the rio Paraíba do Sul basin, though this difference is probably merely a phenotypic variation associated with the black waters where the Brycon opalinus population from the Rio Doce basin dwell (see color variation of B. howesi , B. dulcis , and B. nattereri for similar instances of dark and clear-colored populations). Since there is considerable overlap in morphometric data and no clear geographical patterns in the variation observed, we consider that all these populations should be considered a single species. Analyses of the variability of mitochondrial DNA ( Hilsdorf et al., 2002) and microsatellite loci ( Barroso et al., 2005) indicated some genetic variation among distinct Brycon opalinus populations from the upper and middle rio Paraíba do Sul basin which are, however, within the variability expected in a species with a low genetic interchange.

Ecological notes. Brycon opalinus is exclusively found in headwater areas, inhabiting small rivers, characterized by possessing slightly dark-stained to clear waters, and lentic stretches alternated with rapids, as the rio Paraibuna in the upper rio Paraíba do Sul basin, the rio Preto at the middle portion of the same river system, and the rio Santo Antônio in the upper rio Doce basin. The diet of the species in the upper rio Paraibuna basin was studied by Gomiero et al. (2008), based on the examination of 256 Brycon opalinus stomach contents collected along a whole year. Brycon opalinus is an omnivore, ingesting animal and vegetal food items in about equal proportions, except for the juveniles, that show a tendency to ingest a greater proportion of animal food itens ( Gomiero et al., 2008). Insects (mainly allochthnous), fruits and seeds were the main food itens found in stomach contents ( Gomiero et al., 2008). An exceptional occurrence of frogs and a rat in stomach contents of Brycon opalinus in the upper rio Paraibuna was ascribed to have been caused by a rainstorm, which probably washed these animals into the river ( Gomiero et al., 2006). Stomach contents of two examined specimens (MZUSP 59279, 195.9 mm SL; MZUSP 59280, 247.1 mm SL) from rio Santo Antônio basin was composed by crushed fruits and seeds and a beetle. Specimens collected at the rio Preto, presented stomach contents filled with larvae of Corydalidae ( Megaloptera , Insecta; A. Hilsdorf, pers. comm.). Reproduction of Brycon opalinus was studied by Gomiero & Braga (2007a, b) in the upper rio Paraibuna basin. As other Brycon species, B. opalinus is a total spawner, presenting two reproductive peaks, one during the spring/summer and other during the autumn ( Gomiero & Braga, 2007a). Individuals in breeding condition collected in other river basins confirm that reproduction occurs both during the summer and autumn, as evidenced by a mature male, with well-developed testicles and anal-fin hooks, colected at the rio do Peixe (middle rio Paraíba do Sul basin) during end of April and early May (MZUSP 50805), and a mature female, with oocytes at the urogenital opening, collected at the rio Preto do Itambé (upper rio Doce basin) in March (MZUSP 59282). Sexual maturity is achieved at its earliest with 16 cm TL, and mean fecundity was estimated as 9190 oocytes ( Gomiero & Braga, 2007a). Females grow larger than males, and the sex-ratio is skewed towards females ( Gomiero & Braga, 2007a, b). Specimens kept in captivity achieved the sexual maturity at the second year of age (Narahara, 1993). It is evident that, contrary to some of its congeners, Brycon opalinus does not perform long-distance reproductive migrations, though local migrations might occur in the upper rio Paraibuna (J.P. Villani, pers. comm., 1996). Similarly to some centro-american Brycon species ( Kramer, 1978; Bussing, 1993), spawning in the upper rio Paraibuna occurs in small streams (J.P. Villani fide Gomiero & Braga, 2007b). Growth and mortality parameters of Brycon opalinus in the upper rio Paraibuna basin were estimated by Gomiero et al. (2007) using total-length size classes frequencies. These authors inferred that growth slows during late winter/early spring and that longevity for males and females was 4.50 years. Those growth and aging estimates need to be however validated using more empirical methods such as analyses of ring growths of otoliths and scales (see Pauly, 1987, for a critique on statistical aging methods).

Conservation. Brycon opalinus was presumably originally widely distributed across the rio Paraíba do Sul and rio Doce headwaters areas. Its current geographical range is highly fragmented and restricted to some headwater tributaries of the rio Paraíba do Sul and rio Doce basins. A healthy population of the species occurs within the limits of the Santa Virgínia unit of the Serra do Mar State Park. There are some other healthy populations of the species occurring in some areas, such as the ones occurring at the rio Preto basin in the middle rio Paraíba do Sul basin and at the rio Santo Antônio in the upper rio Doce basin, which unfortunately lack formal protection and are threatened by several ongoing anthropogenic activities, specially hydroelectric dams building. Stocking and reintroduction programs using population genetics information are under way for the species ( Hilsdorf et al., 2002; Barroso et al., 2005). The species is formally considered as threatened with extinction in Brazil, under the category “Vulnerable” (see Hilsdorf, Lima & Vieira, 2008 for additional information). The recent catastrophic burst of a tailings dam in the upper rio Doce in November 2015, which released millions of tons of iron waste into the rio Doce basin and devastated his entire course, probably had no impact on the Brycon opalinus populations of this basin since they are restricted to some tributaries (rio Santo Antônio and rio Piranga) which were not directly affected by the iron waste.

Remarks. Cuvier (1819: 351–352) described Chalceus opalinus based on a specimen collected by the botanist Auguste de Saint-Hilaire at an unspecified locality in Brazil. Valenciennes (in Cuvier & Valenciennes, 1850: 244– 246) redescribed a species based on two specimens, one collected at the “Rio Tiquilenhonha” (= rio Jequitinhonha), which was also collected by Saint-Hilaire, and another specimen from “Rio Janeiro”, collected by “M. de Lalande”. Although Valenciennes (in Cuvier & Valenciennes, 1850) based his description of Chalceus opalinus on the specimen from the rio Jequitinhonha, this specimen certainly does not correspond to the specimen studied by Cuvier (1819) because it was donated to the MNHN in August 1822 (Valenciennes, in Cuvier & Valenciennes, 1850: 246). In fact, the specimen collected by “de Lalande”, MNHN A. 8613, was, as previously remarked by Bertin (1948) and Géry & Mahnert (1992: 813) the one studied by Cuvier (1819), being, thus, the holotype of Chalceus opalinus . Pierre Antoine Delalande travelled with Saint-Hilaire to Brazil and accompanied him from Rio de Janeiro city to “Ubá”, a port at the banks of the rio Paraíba do Sul, and then returned to the Rio de Janeiro city and from there to France, carrying the collections obtained during this travel ( Papavero, 1971). This probably explains why Cuvier (1819) mentioned Saint-Hilaire, instead of Delalande, as being the collector of the holotype of Chalceus opalinus . As earlier remarked by Eigenmann (1921: 294–295), the type locality of Chalceus opalinus should thus be restricted to “Rio de Janeiro”. It is thus very likely that the precise type-locality of Brycon opalinus is the rio Paraíba do Sul at “Ubá” (currently Andrade Pinto, 22°14’S, 43°25’W) where Saint-Hilaire and Delalande spent some time collecting insects ( Papavero, 1971: 116). As for the specimen MNHN A.8612, collected in the rio Jequitinhonha, it undoubtedly represents Brycon howesi (see item “Remarks” of this species, above).

Günther (1864: 334) described Brycon bahiensis bearing the vague type-locality “Bahia”. Localities known as have been sampled by the collector of the holotype of Brycon bahiensis, Otho Wucherer , lies in the neighborings of Salvador (the capital of Bahia state) and some coastal localities southward from it (Nazaré, Canavieiras, and Ilhéus) ( Günther, 1861, 1863; Wucherer, 1861a, b; 1863a, b). The comparison of the holotype of the species (BMNH 1862.11.23: 26) with Brycon opalinus specimens from the rio Paraíba do Sul and rio Doce basins did not revealed any significative differences between them. Howes (1982: 11) remarked that the holotype of Brycon bahiensis possess more premaxillary and maxillary teeth than a Brycon opalinus specimen from Porto Real, Rio de Janeiro (BMNH 1912.11.21: 1). Examination of a large sample of Brycon opalinus in the present study demonstrated that premaxillary counts of the holotype of B. bahiensis lies within the variation of B. opalinus , while the maxillary teeth number is only slightly above the range of variation found in B. opalinus (24, vs. 10–22, respectively). In spite of the fact that the presumable type-locality of Brycon bahiensis lies well outside the known geographical range of Brycon opalinus , we herein consider the former a junior synonym of the latter. Coastal river systems between Salvador and the rio Jequitinhonha mouth, which is the presumable type-locality area of Brycon bahiensis , are still poorly known and more collecting is necessary to ascertain the occurrence of B. opalinus , or a species close to it, in the area (see also the item “Remarks” of B. devillei and B. vonoi ). At this time we have no better option left other than to consider the type-locality of Brycon bahiensis as probably incorrect, and that somehow its type specimen was collected southwards, within the geographical range of B. opalinus .

Magalhães (1931: 168) recorded Brycon pirapitinga in São Luís do Paraitinga, a locality lying at the upper rio Paraíba do Sul basin. However, the name Salmo pira-pitinga Kner (ex Natterer) (1860) is invalid, since it was originally proposed as a synonym of Chalceus opalinus . Both the common name and the locality mentioned by Magalhães (1931) leaves no doubt that his record refers to Brycon opalinus .

Several authors, starting with Steindachner (1877: 27–29), incorrectly identified specimens of Brycon opalinus from the rio Paraíba do Sul and rio Doce basins as Brycon reinhardti (which is a synonym of B. nattereri , see the item “Remarks” of this latter species).

Brycon opalinus was recorded by Bejarano et al. (2006) and Blanco-Parra & Bejarano-Rodríguez (2006) from the Río Mesay, a tributary of the Río Caquetá, Departamento Caquetá, Colombia. The inclusion of the species in a checklist of freshwater fishes from Colombia by Maldonado-Ocampo et al. (2008) was very probably prompted by this record from the Río Mesay. The examination of pictures of the voucher specimen deposited by Bejarano et al. (2003) (ICN-MHN 4262) kindly supplied by J.I.Mojica demonstrated that this record actually refers to Brycon pesu .

Material examined. Type material. MNHN A. 8613 (1, 278 mm SL): “Brésil” [corrected to Rio de Janeiro by Eigenmann, 1921; see “Remarks”, above, for the probable precise locality]; P.A. Delalande & A. Saint-Hillaire, 1816. Holotype of Chalceus opalinus Cuvier. BMNH 1862.11.23: 26 (1, 128.2 mm SL): “Bahia”; O. Wucherer. Holotype of Brycon bahiensis Günther, 1864 .

Additional material. Brazil, São Paulo, rio Paraíba do Sul basin: MZUSP 21872 (12, 68.9–213.4 mm SL): rio Paraibuna, Alto da Serra ; CESP personnel, May 1982. MZUSP 42059 (8, 84.4–239.0 mm SL): Paraibuna, Represa de Paraibuna ; CESP personnel, no date. MZUSP 28338 (9, 146.9– 181.4 mm SL): Paraibuna , CESP fish hatchery; CESP personnel, 16 Feb 1984. MZUSP 51361 (2, 130.0– 170.2 mm SL): São Luiz do Paraitinga, rio Paraibuna , Salto Grande, 23°20’S, 45°9’W ; CESP personnel, no date. MZUSP 46783 (1, 94.3 mm SL): São Luiz do Paraitinga, rio Turvo (trib. rio Paraibuna ); R.S. Lima & I.C. Possagnolo, 26 Jul 1992 . MZUSP 51358 (5, 131.4– 158.6 mm SL): São Luiz do Paraitinga, rio Paraibuna, Salto Grande, Santa Virgínia, Serra do Mar State Park , 23°20’S, 45°9’W ; F.C.T. Lima et al., 2–3 Nov 1996. MZUSP 19127 (5, 135.4– 233.2 mm SL): Silveiras, rio Itaguaçaba basin, fazenda Marrano , c. 22°39’S, 44°51’W ; Jabes T. Braga, May 1981. LBP 6303 (1, 148.8 mm SL): Areias, rio Itagaçaba , 22°39’26’’S, 44°45’50’’W ; R. Devidé et al., 1 Apr 2008. Rio de Janeiro, rio Paraíba do Sul basin: MZUSP 16624 (1, 133.7 mm SL): Resende, rio Paraíba do Sul; P. Azevedo, 1962 . MNRJ 11273 (1, 103.3 mm SL): rio Preto (bacia do Paraíba do Sul), Bagagem , Bocaina de Minas and Resende border, 22°15'S, 44°20'W; G.W. Nunan & W.D. Bandeira, 19 Sept 1982 . MNRJ 11255 (5, 97.1–188.9 mm SL): rio Preto (bacia do rio Paraíba do Sul), 1.5 km downstream Resende-Bocaina de Minas road, borderline RJ/MG, c. 22°15'S, 44°20'W ; J.R.S. Araújo, 6 Sept 1982. MNRJ 11255 (12, 75.3–208.9 mm SL): Resende, rio Preto, Bagagem-Fumaça road, c. 2 km from road Resende / Bocaina de Minas , c. 22°15'S, 44°20'W ; J.R.S. Araújo, 22 Aug 1982. MNRJ 11256 (2. 93.5– 160.0 mm SL): Resende, rio Pirapitinga (bacia do rio Paraíba do Sul), 3–4 km above Fazenda Monte Alegre; J.R.S. Araújo, 6–7 Sept 1982 . MZUSP 83433 (2, 205.0–272.0 mm SL): Rio das Flores, rio Preto , c. 22°5’S, 43°33’W ; B.P. Nogueira & G.V. Padilha, 19 Jul 2000. BMNH 1912.11.21:1 (1, 155.4 mm SL): Porto Real, 22°25’S, 44°17’W ; M. Hardy de Dréneuf. MNRJ 12227 (1, 94.3 mm SL): Teresópolis, rio Preto, at the confluence with rio Paquequer ; D.F. Moraes Jr, 1980 . MNRJ 15291 (1, 45.5 mm SL): Carmo, rio Paquequer (trib. left margin rio Paraíba do Sul), c. 1.5 km above bridge on road RJ-160, 21°53’S, 42°38’W; D.F. Moraes Jr. et al., Sept 1989 . MNRJ 6305 (1, 168.5 mm SL): Sapucaia , rio Paraíba [do Sul], 21°56'S, 42°20'W; C. Moreira, Feb 1911 . MNRJ 21469 (1, 102.9 mm SL): Volta Grande , rio Paraíba do Sul, Ilha dos Pombos, 21°50’16’’S, 42°34’56’’W ; W. A. Gosline, 12–14 Jan 1945 . MCZ 21123 (1, 210.5 mm SL): Rio de Janeiro, Posse, on the valley of the rio Parahyba [rio Piabanha at Posse ], 22°23’S, 43°01’W ; C. Taylor, Thayer Expedition, 1865. MCZ 21113 (2, 114.8–253.0 mm SL): Mendez (Rio Paraíba do Sul or tributary at Mendes ), 22°32'S, 43°44'W ; C. Hartt & E. Copeland, 1865. Minas Gerais, rio Paraíba do Sul basin: MZUSP 42443 (2, 1 cs, 106.7–138.2 mm SL): Olaria, rio Pari , c. 21°51’S, 43°52’W ; collector and date unknown. MZUSP 50805 (8, 128.8– 274.5 mm SL); MZUSP 50803 (1, 58.9 mm SL): Torreões, rio do Peixe , near dam, 21°53’15’’S, 43°32’29’’W ; F. A. Bockmann & A. Akama, 24 April–1 May 1996. MZUSP 50800 (1, 80.5 mm SL): Torreões, rio do Peixe, near the bridge; F . A. Bockmann & A. Akama, 30 April 1996. MZUSP 50806 (2, 143.8– 156.1 mm SL): Torreões, rio do Peixe at sítio da Jacutinga, “fazenda do Tião Belo”; F . A. Bockmann & A. Akama, 30 April–1 May 1996 . MZUSP 50804 (1, 64.7 mm SL): Minas Gerais, Torreões, córrego Jacutinga, tributary of rio do Peixe ; F . A. Bockmann & A. Akama, 30 April 1996. MZUSP 89510 (1, 77.3 mm SL, cs): Torreões, rio do Peixe , c. 21°53’S, 43°32’W ; F. A. Bockmann & A. Akama, Apr 1996. MZUSP 107915 (1, 227.0 mm SL): Juiz de Fora, rio do Peixe, UHE Picada , c. 21°52' S, 43°33’W ; C. Leal & M. Santos, 28 March 2009. MZUSP 83432 (1, 146.7 mm SL): Rio Preto, ribeirão Santana (trib. rio Paraíba do Sul), c. 22°2’S, 43°46’W ; B.P. Nogueira & G. A. Pereira, 7 Dec 2002. MNRJ 14781 (1, 118.2 mm SL): Santana do Deserto, rio Cágado , trib . rio Paraibuna , 21°59’S, 43°8’W; D.F. Moraes Jr. et al., 29 Jun 1989 . ZUEC 6380 (1, 139.7 mm SL): Rio Pomba, rio Pomba , 21°18’0’’S, 43°12’18’’W; D.M. Rosa, May 2010 . Minas Gerais, rio Doce basin : MCZ 21130 (1, 241.1 mm SL): “ Rio Santo Antonio, Santa Anna de Ferros ” [Rio Santo Antonio (tributary of Rio Doce) at Ferros ], 19°13'S, 43°1'W ; T. Ward, 1865. MZUSP 100262 (2, 96.6–203.0 mm SL): Ferros, rio Santo Antônio , c. 19°13'S 43°1'W ; C. Lima & H. Aguiar, 8 March 2008. MZUSP 51051 (1, 203.5 mm SL): Itambé do Mato Dentro, rio Preto do Itambé , 19°24’40’’S, 43°18’41’’W ; J.C. Garavello et al., no date. MZUSP 59282 (3, 119.6– 249.4 mm SL): Itambé do Mato Dentro, rio Preto do Itambé, trib. rio Santo Antônio , 19°24’40’’S, 43°18’41’’W; F. Vieira et al., 12 March 1994 . MZUSP 59284 (3, 1 cs, 98.1–125.5 mm SL): Morro do Pilar, rio Preto, trib. rio Santo Antônio , 19°14’S, 43°20’W; F. Vieira et al., 13 March 1994 . MZUSP 59285 (1, 93.9 mm SL): Itambé do Mato Dentro, rio Preto do Itambé, trib. rio Santo Antônio , 19°24’40’’S, 43°18’41’’W; F. Vieira et al., 27 Aug 1994 . MZUSP 59281 (2, 89.1–199.3 mm SL); UFMG uncataloged (1, 120.5 mm SL): Morro do Pilar, rio Preto, trib. rio Santo Antônio , 19°14’S, 43°20’W; F. Vieira et al., 28 Aug 1994 . MZUSP 59283 (1, 158.0 mm SL): Itambé do Mato Dentro, rio Preto do Itambé, trib. rio Santo Antônio , 19°24’40’’S, 43°18’41’’W; F. Vieira et al., 26 Nov 1994 . MZUSP 59280 (2, 215.5– 247.1 mm SL): Morro do Pilar, rio do Peixe, trib. rio Preto do Itambé ; F. Vieira et al., 14 Sept 1996 . MZUSP 59279 (3, 132.7– 195.9 mm SL); UFMG uncataloged (1, 175.4 mm SL): São Sebastião do Rio Preto, rio Preto do Itambé , below rio do Peixe mouth; F. Vieira et al., 15 Sept 1996 . MZUSP 59286 (5, 25.9–29.2 mm SL): rio Preto do Itambé, trib. rio Santo Antônio , 19°24’40’’S, 43°18’41’’W; F. Vieira et al., 25 Aug 1991 . MZUSP 73104 (1, 232.6 mm SL): São Sebastião do Rio Preto, rio Santo Antônio, road to Córrego da Fonseca, approx. 11 km from Santo Antônio , c. 19°16’S, 43°10’W; F. Di Dário & S. Kakinami, 12 Sept 2001 . MZUSP 73119 (1, 35.9 mm SL): Santo Antônio do Rio Abaixo, rio Santo Antônio, Benedito Martins beach, 19°13’22’’S, 43°15’17’’W ; F. Di Dário, 14 Sept 2001. MZUSP 75309 (2, 55.3–68.3 mm SL); MZUSP 75310 (1, 82.5 mm SL): Conceição do Mato Dentro, rio Santo Antônio , fazenda das Campinas, road MG 0 10, km 158, 19°4’56’’S, 43°25’53’’W; F. Di Dário & B. Di Dário, 17–18 Dec 2001 . UMMZ 216714 (1, 119.6 mm SL): “ Rio Doce: creeks, pools and river” [= rio Xopotó at Alto rio Doce , 21°1’S, 43°24’W]; J.D. Haseman, 26 May 1908 . MZUSP 59287 (1, 163.2 mm SL): Ponte Nova, rio Piranga , c. 20°25’S, 42°55’W; J.C. Garavello & A. S. Soares, 28 May–4 June 1995 . Rio Paraíba do Sul basin, no precise locality: UMMZ 216713 (4, 104.6– 152.5 mm SL) ; UMMZ 216712 (4, 149.4– 172.7 mm SL); MCZ 21119 (1, 77.3 mm SL); MCZ 21118 (3, 192.2– 223.1 mm SL); MCZ 21120 and MCZ 21121 (10, 71.0– 154.7 mm SL); NMW 62733 (3, 118.6– 131.4 mm SL): “ Rio Parahyba ”; Thayer Expedition, 1865. Uncertain locality (see Remarks ) : MCZ 21104 (2, 59.2–62.2 mm SL): “ Rio Doce” [Rio Doce, between Linhares and Aimorés], 19°37'S 39°49'W; C.F. Hartt & E. Copeland, 1865.

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 38. Brycon opalinus, holotype, MNHN A. 8613, 263.0 mm SL: Brazil, “ Rio de Janeiro ”. Photo by A. M. Zanata.

FIGURE 39. Brycon opalinus, BMNH 1862.11.23: 28, 128.2 mm SL: Brazil, “ Bahia ”. Holotype of Brycon bahiensis Günther.

FIGURE 40. Brycon opalinus, MZUSP 19127, 233.2 mm SL: Brazil, São Paulo, rio Itaguaçaba.

FIGURE 41. Brycon opalinus, MZUSP 50805, 274.5 mm SL: Brazil, Minas Gerais, rio do Peixe (rio Paraíba do Sul basin).

FIGURE 42. Brycon opalinus, MZUSP 59280, 247.7 mm SL: Brazil, Minas Gerais, rio do Peixe (rio Doce basin).

FIGURE 43. Map of central and eastern Brazil, showing known localities of Brycon opalinus (black dots), and B. nattereri (red dots).

Tables

TABLE 12. Morphometric data of Brycon opalinus (A: holotype, MNHN A. 8613; B: holotype of Brycon bahiensis, BMNH 1862.11.23.26). Mean and range does not include holotype (which is a stuffed specimen).

	A	B	n	Range	Mean
Standard length (SL)	278.0	128.2	94	58.9–274.5	-
Percentages of standard length
Depth at dorsal-fin origin	25.3	28.7	91	21.3–32.8	27.2
Snout to dorsal-fin origin	51.2	52.0	94	45.6–57.0	51.7
Dorsal-fin base length	10.5	12.8	93	9.6–13.1	11.2
Posterior terminus of dorsal fin to adipose fin	23.7	23.4	93	20.2–27.3	23.5
Posterior terminus of dorsal fin to hypural joint	34.9	34.8	93	30.1–39.8	36.1
Snout to pelvic-fin insertion	50.4	47.0	93	45.8–55.0	50.5
Snout to anal-fin origin	70.6	66.8	94	60.6–74.4	66.5
Anal-fin base length	19.3	22.8	94	17.1–25.8	20.7
Caudal peduncle length	10.4	12.6	94	13.6–20.5	16.8
Dorsal-fin height	-	21.6	93	14.5–22.8	17.9
Pectoral-fin length	-	20.0	94	11.7–20.2	16.6
Pelvic-fin length	12.3	16.1	93	9.4–16.1	13.3
Caudal peduncle depth	8.7	9.0	94	6.9–10.3	8.9
Head length	26.8	25.8	94	21.5–31.7	25.2
Percentages of head length
Head height	-	75.8	94	67.2–88.4	76.5
Snout length	27.1	27.8	94	22.9–33.3	28.6
Upper jaw length	46.1	46.5	94	38.7–48.3	42.9
Horizontal eye diameter	20.9	29.3	94	21.0–34.4	26.4
Post-orbital length	53.2	46.2	92	42.7–52.2	48.3
Least interorbital width	28.8	37.2	93	24.5–41.1	33.9