Bryconops tocantinensis, Guedes & Oliveira & Lucinda, 2016

Guedes, Tharles L. O., Oliveira, Everton F. & Lucinda, Paulo H. F., 2016, A new species of Bryconops (Ostariophysi: Characiformes: Characidae) from the upper rio Tocantins drainage, Brazil, Neotropical Ichthyology 14 (2), No. e 150176, pp. 1-8 : 2-6

Bryconops tocantinensis , new species

u r n:lsid:zooba n k.org:a ct: DA0E050F-E8A A-414A-9BCE - 1A08BA312B55

Figs. 1-4

Holotype. MCP 49199, male, 53.7 mm SL, Brazil, Tocantins, Taguatinga, rio Conceição (tributary of rio Palma , upper rio Tocantins drainage), 12°19’48.30”S 46°25’4.20”W, 17 Jul 2014, E. F. Oliveira, L. B. S. Araujo, T. L. O. Guedes & J. E. C. Rocha.

Paratypes. Brazil. Tocantins. MCP 49200, 24 , 32.0- 64.5 mm SL , MNRJ 44220 , 20 , 28.8 -62.0 mm SL ; MZUSP 118553 , 11 , 30.8-38.9 mm SL, and UNT 12791, 45 (14 c&s), 27.4-65.0 mm SL, collected with the holotype . MZUSP 114466 , 10 , 21.5-48.3 mm SL, same locality as holotype, 2 Dec 2012 , O. T. Oyakawa, A. M. Zanata, P. Camelier & M. Melo .

Diagnosis. Bryconops tocantinensis is distinguished from all species of genus Bryconops , except B. humeralis Machado-Allison, Chernoff & Buckup and B. vibex Machado-Allison, Chernoff & Buckup by the color pattern in vivo (dorsal, adipose, and caudal fins entirely orange). Bryconops tocantinensis is easily distinguished from B. humeralis and B. vibex by the absence of humeral spot and by the lack of maxillary teeth (vs. presence of a single humeral spot and presence of 1-3 maxillary teeth on both sides). Furthermore, B. tocantinensis is distinguished from B. inpai Knöppel, Junk & Géry , and B. munduruku Silva- Oliveira, Canto & Ribeiro by the absence of humeral spot (vs. two spots). Bryconops tocantinensis is distinguished from B. disruptus Machado-Allison & Chernoff, B. durbini (Eigenmann), B. piracolina Wingert & Malabarba, B. giacopinii (Fernández-Yépez), B. magoi Chernoff & Machado-Allison, B. collettei Chernoff & Machado- Allison, B. vibex, B. transitoria (Steindachner) , B. gracilis (Eigenmann) , and B. alburnoides Kner by the number of perforated lateral line scales (38-41 vs. 9-23, 30, 31-36, 43- 46, 43-47, 43-48, 44-46, 45-46, 54, and 57-61 perforated lateral line scales, respectively). Bryconops tocantinensis is distinguished from B. melanurus (Bloch), B. colaroja Chernoff & Machado-Allison, B. imitator Chernoff & Machado-Allison, B. colanegra Chernoff & Machado- Allison, and B. affinis (Günther) by the lack of maxillary teeth (vs. presence of 1-3 maxillary teeth on both sides in the five species just mentioned above). Bryconops tocantinensis is distinguished from B. melanurus by the color pattern of the middle caudal-fin rays (slightly darkened vs. densely darkened, respectively; see Chernoff et al., 1994: fig. 2). Bryconops tocantinensis is further distinguished from B. melanurus, B. colaroja, B. colanegra, and B. imitator by the presence of an ocellus on upper lobe of the caudal fin (vs. absence of such ocellus in the four species just mentioned above). Bryconops tocantinensis is further distinguished from B. affinis by the absence of an ocellus on lower lobe of the caudal fin (vs. presence of such ocellus in B. affinis ). Bryconops tocantinensis is distinguished from B. cyrtogaster (Norman) by the number of branched anal-fin rays (20-25 vs. 28-29). Bryconops tocantinensis is distinguished from B. caudomaculatus (Günther) by the horizontal eye diameter (12.3-14.4% SL vs. 9.0-12.0% SL), and by the number of scale rows around caudal peduncle (16 vs. 12-14).

Description. Morphometric data presented in Table 1. Moderate to small-sized species of Bryconops , largest specimen examined 65.0 mm SL. Elongate body, laterally compressed. Greatest body depth at dorsal-fin origin. Dorsal body profile convex from snout to vertical through anterior nostrils; straight or slightly convex from posterior nostrils to tip of supraoccipital bone; convex from this point to dorsal-fin origin. Straight and posteroventrallyaligned along dorsal-fin base; postdorsal profile straight from base of last dorsal-fin ray to adipose-fin origin and concave from latter point to end of caudal peduncle. Ventral profile convex from snout to pelvic-fin insertion; straight or slightly convex from this point to anal-fin origin; straight and posterodorsally-aligned along anal-fin base; postventral profile concave from base of last anal-fin ray to end of caudal peduncle.

Head large. Posterior margin of opercle slightly sinusoidal. Mouth terminal. Premaxilla and dentary positioned at same level, or premaxilla slightly longer than dentary. Snout shorter than eye diameter. Eyes large. Adipose ocular membrane well-developed. Maxilla moderately enlarged, its distal portion not reaching articulation between second and third infraorbitals, and not reaching vertical through middle of orbit. Anteroventral margin of maxilla describing a semicircle just ventral to ascending process. Second and third infraorbitals articulating only dorsally, leaving a naked area in their ventral margins; third infraorbital moderately developed, not reaching preopercle ventrally or at its angle. Antorbital present, bearing well-developed infraorbital sensory canal. Supraorbital bone present, contacting antorbital anteriorly, not reaching sixth infraorbital posteriorly. Six infraorbital bones ( Fig. 2 ). Branching of laterosensory canal of fourth infraorbital present (see Mirande, 2010: 407; fig. 39).

Two rows of premaxillary teeth with central cusp larger than lateral ones. Teeth of external row of premaxilla approximately of same size. Three (2) or 4(6) tri- or pentacuspid teeth in external row of premaxilla. First teeth pentacuspid; second, third and fourth teeth with three or five cusps. In specimens with four teeth on external row of premaxilla, third one slightly more internal than remaining. Five (8) tetra- to heptacuspid teeth in internal row of premaxilla. First teeth tetra- to hexacuspid; second and third teeth with six or seven cusps; fourth tooth penta- or hexacuspid; fifth tooth tetra- or pentacuspid. Left maxilla with 0(50), 1(1), or 2(1) conical teeth. Right maxilla without teeth (52). Five (8) anteriormost dentary teeth larger, followed by 4(1), 5(4), 6(1), 7(1), 8(1) smaller teeth. Anterior large teeth of dentary with two to seven cusps. First, second, and third teeth hexa- or heptacuspid; fourth tooth penta- to heptacuspid; fifth tooth with two, four or five cusps. Largest cusp of fifth tooth strongly curved to oral cavity. First small teeth of dentary conical or bicuspid, remaining small teeth conical ( Fig. 3 ).

Dorsal-fin rays ii,8(1) or ii,9*(56). Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion, near middle of body. Length of first unbranched dorsal-fin ray less than half length of second unbranched ray. First and second branched rays longest. Posterior margin of dorsal-fin straight to sinusoidal. Adipose-fin origin approximately at vertical through base of 18 th to 22 th branched anal-fin rays; adipose fin with convex dorsal margin and straight ventral margin. Pectoral-fin rays i,10(2) or i,11*(55). Tip of pectoral fin not reaching pelvic-fin origin, when adpressed. Pelvic-fin rays i,7*(57). Tip of pelvic fin usually reaching anal-fin origin, when adpressed (in all males tip of pelvic fin reaches anal-fin origin). Anal-fin rays ii,23(1), iii,23(2), iv,20(1), iv,22(6), iv,23(31), iv,24*(15), or iv,25(1). Anal-fin origin located posterior to vertical through base of last dorsal-fin ray. Sheath of small scales with approximately 3 scales arranged in single row along anterior portion of analfin base. Principal caudal-fin rays 19*(52) or 20 (5). Caudal fin naked and forked, lobes of caudal fin unequal, upper lobe with rounded tip, lower lobe longer and more pointed.

Scales cycloid, wider than long. Scale in lateral line with few radii (2), slender and long; circuli marked anteriorly and marginally (dorsal and ventral), scale with pore in its central portion. Scale sampled immediately above lateral line with same patterns of radii and circuli described above, but without pore in its central portion. Predorsal scales 9(1), 10(11), 11*(37), or 12(4) arranged in regular series. Incomplete lateral line ventrally curved along its first third; originating approximately on dorsal portion of opercle. Total scales in longitudinal series containing perforated and nonperforated lateral line scales 41(2), 42(9), 43(18), 44(23), or 45*(4). Perforated lateral line scales 38(7), 39(17), 40(24), or 41*(9). Non-perforated lateral line scales 2(4), 3(17), 4*(27), or 5(8). Scale rows between dorsal-fin origin and lateral line 7*(56) or 8(1). Scale rows between lateral line and pelvic-fin insertion 3*(52) or 4(5). Axillary scale present. Scale rows between lateral line and anal-fin origin 3(2) or 4*(53). Scale rows around caudal peduncle 16*(57).

Precaudal vertebrae 18(8). Caudal vertebrae 22(8). Total vertebrae 40(8). First dorsal-fin pterygiophore between 10 th and 11 th (4) or 11 th and 12 th (3) vertebrae. First anal-fin pterygiophore between 18 th and 19 th (8) vertebrae. Supraneurals 6(8). First supraneural inserted anterior to neural spine of 4 th centrum and last supraneural inserted anterior to first dorsal-fin pterygiophore. Dorsal procurrent caudal-fin rays 12(3) or 13(5). Ventral procurrent caudal-fin rays 12(4) or 13(4).

Gill rakers of first gill arch 16(2), 17(3), or 18(1): hypobranchial 2(4) or 3(2), between hypobranchial cartilage and ceratobranchial 0(3) or 1(3), ceratobranchial 6(3) or 7(3), between epibranchial cartilage and ceratobranchial 1(6), epibranchial 6(3) or 7(3). Branchiostegal rays 4(5) or 5(1): 3(5) or 4(1) on ceratohyal, 1(6) on epihyal. Gill rakers setiform. Gill rakers of first gill arch between epibranchial cartilage and ceratobranchial, setiform, ossified only at its basal portion and with few denticulation.

Color in alcohol. Males and females with same color pattern. Overall ground coloration of body dark yellow to slightly brown. Dorsum of head, snout, lower lip and anterior portion of maxilla dark brown. Infraorbitals silvery white. Gular area and posterior portion of maxilla yellowish or whitish. Dentary with frontal portion blackish and ventral portion yellowish. Orbit whitish with dark pupil. Dorsal profile between tip of supraoccipital bone and insertion of uppermost caudalfin ray dark. Dorsolateral scales with reticulated pattern due to higher concentration of melanophores at their distal borders. Dark brown midlateral stripe narrow anteriorly and progressively expanding from head to under dorsal fin; then becoming slightly narrower towards middle caudal peduncle; and then broadening on distal portion of caudal peduncle, merging to diffuse, oblong darkened caudal spot. Midlateral stripe reaching greatest depth at vertical through end of dorsal-fin base, occupying 2 or 2.5 scales rows wide above lateral line. Presence of darker line on midlateral stripe, most evident between vertical through dorsal-fin origin and vertical through base of last branched anal-fin ray. Ventral portion of body below midlateral stripe yellowish, with many chromatophores scattered between anal-fin base and midlateral stripe. Humeral spot absent. Pores on lateral line being readily visible up to at least vertical through dorsal-fin origin. Dorsal fin hyaline with dark chromatophores along rays. Adipose fin hyaline, without dark chromatophores. Well-developed ocellus on base of upper lobe of caudal fin. Clear area on base of lower lobe of caudal fin without ocellus. Distal portions of upper and lower lobes of caudal fin dark on white background. Middle caudal-fin rays slightly dark. Pectoral and pelvic fins hyaline with few dark chromatophores along rays. Anal fin hyaline with few dark chromatophores on tip of first four rays.

Color in life. Males and females with same color pattern. Dorsal portion of head, snout, and anterior portion of maxilla darker. Lower portion of opercle, preopercle and posterior portion of maxilla whitish to silvery. Lower lip darker. Dentary with frontal portion yellow to orangish, and ventral portion white. External portion of eye clear with dark pupil. Portion between end of supraoccipital bone and insertion of upper caudal-fin rays slightly dark. Dorsolateral portion above midlateral stripe yellow to golden. Brilliant silvery midlateral stripe originating from upper margin of opercle and extending to end of caudal peduncle. Lateral portion of body below midlateral stripe silvery to whitish. Ventral portion whitish. Area near pectoral fin orangish in larger females. Humeral spot absent. Perforated lateral line scales readily visible. Dorsal and adipose fins entirely orange. Caudal fin orange in both upper and lower lobes. Well-developed ocellus on base of upper lobe of caudal fin. Upper and lower lobes of caudal fin with scattered dark chromatophores on background orange, conferring stronger intensity to orange color relative to middle caudal-fins. Dark chromatophores even more concentrated on distal portions of both lobes. Orange color of middle caudal-fin rays much lighter. Distal portion of pectoral-fin rays orange (only in larger females> 55 mm SL). Distal portion of pelvic-fin rays orange. Distal portion of anal-fin rays orange only next to first branched anal-fin ray. Remaining areas of pectoral, pelvic, and anal fins hyaline ( Fig. 4 ).

Sexual dimorphism. Males and females with same morphological pattern. Mature males of Bryconops tocantinensis are easily recognized by the presence of bony hooks on the anal and pelvic-fin rays. The smallest specimen bearing hooks on pelvic and anal fins has 37.7 mm SL. Analfin hooks are small and spine-like and distributed along only the distal half of the fin rays up to the fifteenth branched ray. Number of hooks decreasing from last unbranched ray to fifteenth branched ray. Pelvic-fin hooks larger and spine-like; present on first six branched rays. Distal portion of pectoralfin rays orange (only in larger females> ca. 55 mm SL).

Geographic distribution. Bryconops tocantinensis is known from its type locality, rio Conceição , a tributary to the rio Palma, upper rio Tocantins drainage, Tocantins, Brazil ( Fig. 5 ). Etymology. The specific name, tocantinensis , is an adjective and refers to the rio Tocantins drainage, where this species is currently known to occur .

Remarks. The predominant condition of maxilla in Bryconops tocantinensis is edentulous. However, among the fifty-two specimens examined, only one specimen exhibited two conical teeth on the left maxilla and additional one exhibited just one conical tooth on the same side.

Conservation status. Considering that, although its known geographic distribution is restricted, current relevant threats to the species were not detected in its distribution area, Bryconops tocantinensis could be classified as Least Concern (LC), according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2016). Further studies on biology, ecology and distribution of the species could detect plausible threats to the population of Bryconops tocantinensis , perhaps leading to a revaluation of the conservation status of the species.

Ecological notes. The type locality is around 554 m above sea level. Bryconops tocantinensis inhabits stream, and occurs in lotic shallow areas (up to 1.5 m deep) with riparian vegetation composed by trees and shrubs ( Fig. 6 ). The stream has transparent water, and bottom with sand, stones, and rocks. The new species was syntopically collected with Eigenmannia trilineata , Hoplerythrinus unitaeniatus , Astyanax cf. goyacensis , Knodus cf. breviceps , Knodus sp. , and Ancistrus sp. The collection occurred between 11:00 a.m.-1: 30 p. m. with trawl.

Figures

Fig. 1. Bryconops tocantinensis, new species, MCP 49199, holotype, male, 53.7 mm SL, Brazil, Tocantins, Taguatinga, rio Conceição (tributary of rio Palma, upper portion of rio Tocantins drainage).

Fig. 2. Bryconops tocantinensis, UNT 12791, paratype, female, 54.3 mm SL (c&s). Right lateral view (flipped) of maxilla (MX), infraorbital series (IO1-6), antorbital (AO), and supraorbital (SO). Scale bar = 1 mm.

Fig. 3. Bryconops tocantinensis, UNT 12791, paratype, female, 54.3 mm SL (c&s). Left lateral view of premaxilla, maxilla, and lower jaw. Scale bar = 1 mm.

Fig. 4. Bryconops tocantinensis, female, live specimen, rio Conceição, upper rio Tocantins drainage, Tocantins, Brazil.

Fig. 5. Map showing the type locality of Bryconops tocantinensis, rio Conceição, tributary of rio Palma (upper rio Tocantins drainage), Taguatinga, Tocantins, Brazil.

Fig. 6. Type locality of Bryconops tocantinensis, rio Conceição, tributary of rio Palma (upper rio Tocantins drainage), Taguatinga, Tocantins, Brazil.