Odontostilbe avanhandava, Chuctaya & Bührnheim & Malabarba, 2018

Chuctaya, Junior, Bührnheim, Cristina M. & Malabarba, Luiz R., 2018, Two new species of Odontostilbe historically hidden under O. microcephala (Characiformes: Cheirodontinae), Neotropical Ichthyology 16 (1), pp. 1-22 : 8-11

Odontostilbe avanhandava , new species

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Figs. 7-9

Odontostilbe microcephala non Eigenmann, 1907. - Eigenmann, 1915 [in part]: 94-95 (the largest specimen from CM 6854a-c (FMNH 57871) from rio Tietê at Salto Avanhandava above the falls, São Paulo, Brazil, upper rio Paraná basin).

Holotype. LIRP 3239 , 48.7 mm SL, female, ribeirão da Batalha, farm Batalha (Pedro Quaresma), rio Paranaíba, Paracatu, Minas Gerais State, Brazil, 17°25′25″S 47°27′11″W, 27 Apr 2002, C. A. A. Figueiredo & E. S. S. Rego.

Paratypes. All from Brazil, upper rio Paraná basin. São Paulo State: FMNH 57871 , 1 , 62.1 mm SL, rio Tietê at Salto Avanhandava below the falls, 14 Sep 1908, J. Haseman [material reviewed by Eigenmann (1915)]. LIRP 00314 , 2 , 47.4-51.1 mm SL, rio Pardo, Ribeirão Preto , 15 Oct 1991, W. E. Alvear. MCP 12103, 1 , 56.1 mm SL, Ilha Solteira, rio Paraná , Set 1965 . MCP 26004, 2 , 39.3-57.9 mm SL, rio Paranapanema, at Jurumirim dam reservoir, Itatinga, 23°06′00″S 48°36′00″W, UNESP de Botucatu. Goiás State: MCP 26003, 1 , 43.8 mm SL, rio do Peixe (tributary of rio Corumbá ), rio Paranaíba , Caldas Novas , 17°36′00″S 48°27′00″W, 19 Oct 1996, Nupelia. MCP 26002, 1 , 57.7 mm SL, rio do Peixe, nex to mouth (tributary of rio Corumbá), rio Paranaíba , Caldas Novas , 17°36′00″S 48°27′00″W, 21 Sep 1996, Nupelia. MNRJ 19718 , 1 , 54.2 mm SL, rio São Bento, a tributary of the left margin of the rio São Marcos, downstream of the future AHE Serra dam, Paranaíba basin, Divinópolis , 18°10′10″S 47°38′07″W, 27 Sep 1999, C. A. Figueiredo, F. A. Bockmann & A. P. R. Pires. MZUSP 80112 , 2 , 66.4-77.7 mm SL, Ensecadeira da Usina Hidroeletrica de Corumbá IV, rio Corumbá, Luziânia, H. L. R. Silva. Mato Grosso do Sul State: MCP 12101, 1 , 30.2 mm SL, lakes along of the margin of rio Paraná , in front of Jupiá , 11-23 Sep 1964 .

Diagnosis. Odontostilbe avanhandava differs from its congeners, except of O. weitzmani , by the presence of mesopterygoid teeth, grouped on median portion forming a continuous row, covering half of mesopterygoid bone (vs. absent). Odontostilbe avanhandava is distinguished from O. weitzmani by the presence de 11-12 lamellae in left and right sides of central median raphe of olfactory rosette (vs. 20-21) and from all species of the genus, except O. fugitiva , O. splendida , O. parecis , and O. pao by the presence of teeth with 9 or 11 cusps in the premaxilla, mostly 9, occasionally 7 cusps (vs. 3-7 cusps; teeth with 9 or 11 cusps always absent). Odontostilbe avanhandava is distinguished from O. fugitiva , O. splendida , and O. pao by the subterminal mouth (vs. terminal mouth); additionally from O. parecis and O. fugitiva by the presence of 16-18 branched anal-fin rays, mostly 17 (vs. 20-21 in O. parecis and 19-24, mostly 21-22 in O. fugitiva ); from O. splendida by the anterior position of the adipose fin, positioned at vertical through last analfin ray insertion (vs. at vertical through last 2nd or 3rd anal-fin ray insertions); from O. pao by the presence of 5 scale rows between lateral line and dorsal-fin origin (vs. 6-7, mostly 7).

Description. Morphometric data on Tab. 2 . Body elongate and slightly compressed ( Fig. 7 ). Greatest body depth at vertical through dorsal-fin origin. Snout elongated and round. Dorsal profile of head convex from snout to posterior margin of frontal bone, slightly concave from there to distal tip of supraoccipital bone. Predorsal profile slightly convex from posterior end of supraoccipital to dorsal-fin origin. Dorsal-fin origin located at midlength of SL. Body profile in base of dorsal fin straight and slightly convex from that point to origin of adipose fin. Body profile between adipose-fin base and dorsal procurrent caudalfin rays slightly concave. Ventral profile of head slightly convex from snout to origin of pelvic fins and convex from there to origin of anal fin. Body profile along base of anal fin straight or slightly convex. Ventral profile of caudal peduncle slightly concave. Caudal peduncle slightly longer than deep.

Head small relative to body length, 21.3-24.0% SL. Mouth subterminal, opening oriented forward and somewhat ventrally, in which upper jaw and snout clearly extends beyond lower jaw. Maxilla posteroventrally angled, posterior end surpassing vertical through anterior border of eye and surpassing horizontal through ventral border of eye. Two or 3 maxillary teeth, with 7-9 [mostly 9] cusps nearly of equal size. Premaxilla with a single row of 5-6 teeth slightly inclined to inside mouth ( Fig. 8 ), bearing 7-11 [mostly 9] cusps nearly of equal size. Dentary with 7 or 8 teeth, anterior 6 teeth larger, bearing 7 cusps nearly equal in size, followed posteriorly by 1 or 2 smaller conical teeth, rarely tricuspidate. Dentary teeth inclined anteriorly. Presence of mesopterygoid teeth, grouped on median portion of bone forming a continuous row, covering half-length of ventral surface of mesopterygoid.

Dorsal-fin rays ii,9(14) in all examined specimens. Dorsal-fin origin at vertical of pelvic-fin insertion. Profile of distal margin of dorsal fin slightly concave. First unbranched dorsal-fin ray less that half-length of second, following branched rays gradually decreasing in size posteriorly. Presence of small ossification associated with first proximal dorsal-fin radial (character 124, described by Zanata, Vari, 2005). First unbranched ray of dorsalfin inserted in first pterygiophore and last two branched rays inserted in tenth pterygiophore. Proximal radial of first pterygiophore in contact with neural spine of eleventh precaudal vertebra. Dorsal fin with medial radial fused with distal radial from first to fourth pterygiophore and individualized from fifth to tenth pterygiophore. Proximal radial of first to ninth pterygiophores with lateral projections.

Adipose-fin origin posterior to vertical through base of last anal-fin ray. Unbranched anal-fin rays iv(1); branched anal-fin rays 16(4), 17(8), 18(2), with two rows of scales covering base of anterior 6 branched rays. Anal-fin origin posterior to vertical through base of last ray of dorsal fin. Profile of distal margin of anal fin concave. Anal fin with all unbranched rays associated with first pterygiophore, except last unbranched ray associated with second pterygiophore. Medial radial fused with distal radial from first to fifth pterygiophores, visible from that point to last pterygiophore. Proximal radial of first pterygiophore in contact with hemal spine of first caudal vertebra.

Pectoral fin rays i(14), 11(2), 12(1), 13(5), 14(4), or 15(2). First pectoral-fin ray reaching anterior tip of pelvic bone. Pelvic fin i,7(14) rays; insertion located approximately at vertical through origin of dorsal fin. In mature males, first unbranched ray prolonged in filament, usually surpassing origin of anal fin. Principal caudal fin rays 19(14). Procurrent caudal-fin rays: dorsal 7(3), 8(9), 9(1), or 11(1) rays and ventral with 6(2), 7(4), 8(3), 9(4), or 10(1) rays.

Cycloid scales; pored scales on lateral line 36(1), 37(4), 38 (4), or 39(2). Predorsal scales arranged in a regular series with 11(2) or 12(6) scales; scale rows between lateral line and dorsal line origin 5(14); scales rows between lateral line and pelvic-fin origin 4(14); scale rows around caudal peduncle 14(11).

Supraneurals independent, elongate, rod-like, 5(1). Precaudal vertebrae 17; caudal vertebrae 19; total vertebrae 36. Upper gill rakers 6, lower gill rakers 12(2 on hypobranchial). Upper gill rakers with 6-8 denticles on anterolateral border, and 0-2 denticles on posterolateral border. Lower gill rakers with 7-12 denticles on anterolateral border, and 0-1 denticles on posterolateral border. Gill raker inserted on junction of ceratobranchial and epibranchial with 10 denticles on ventrolateral and 3 on dorsolateral borders ( Fig. 9 ). Olfactory rosette of Odontostilbe avanhandava is more or less circular in shape and consists of 11(1) or 12(1) lamellae in left and right sides of central median raphe.

Scales of dorsal portion of body from supraoccipital to caudal peduncle with small dark dots concentrated on posterior margin. Region posterior of pseudotympanum to caudal peduncle with thin silvery band, dorsal and ventral edges of gray color, chromatophores forming a black band reaching caudal spot. A conspicuous oval horizontally black caudal spot overlapping base of middle caudal fin rays.

Dorsal fin with scattered black chromatophores slightly darker and more numerous on mid-distal portion of dorsal fin, extending from first unbranched dorsal-fin ray to ninth branched fin ray. Pectoral and pelvic fins hyaline. Anal fin with sparse dark dots scattered over all rays, more concentrated in the basal region. Adipose fin unpigmented.

Sexual dimorphism. Mature males with small hooks on pelvic and anal fins. Pelvic–fin with small hooks in all branched rays, with one retrorse bony hook per segment, on mesoventral border of both lepidotrichia in median and distal portions of pelvic fin. Tip of bony hooks not reaching proximal border of segment of lepidotrichia where inserted. Anal–fin rays with one pair of small retrorse bony hooks per segment symmetrically placed, on last unbranched ray and first to fourth branched rays, decreasing in number posteriorly. Bony hooks on median portion of posterior branch (never on anterior branch). Tip of bony hooks not reaching proximal border of segment of lepidotrichia where inserted.

Geographic distribution. Odontostilbe avanhandava is known to inhabit tributaries of the upper rio Paraná basin, in the states of Mato Grosso do Sul, Goiás, Minas Gerais, and São Paulo, Brazil ( Fig. 6 ).

Color in alcohol. Overall body coloration yellowish. Dorsal surface of head from snout to posterior limit of frontal with chromatophores scattered giving a dark yellow coloration. Dark red chromatophores noticeably more concentrated in region of parietal and supraoccipital. Opercular apparatus and infraorbital region silver beige. Branchiostegal rays silver beige. Ventral region between pectoral and pelvic fins with a lighter yellow area. Humeral region with a darkened triangular area due to muscular hiatus of pseudotympanum. Etymology. The epithet avanhandava , refers to the “ Salto do Avanhandava” falls of the rio Tietê, the locality of collection of the oldest known specimen, collected by John D. Haseman in 1908. The toponym Ava - Nhandava means: “Man who speaks the Nhandeva dialect”. The “ Salto do Avanhandava” does not exist anymore and was flooded by the Nova Avanhandava Hydroelectric Power Dam. A name in apposition.

Conservation status. Odontostilbe avanhandava presents the same distribution of Odontostilbe weitzmani . This species is not abundant in scientific collections, but represents a wide distribution in upper rio Paraná basin. Odontostilbe avanhandava may be categorized as Least Concern (LC), according to the IUCN criteria for evaluation on threatening status, version 13 (IUCN, 2017).

Remarks. A specimen of Odontostilbe avanhandava collected in the upper rio Paraná basin was found in the material used by Eigenmann (1915) to redescribe O. microcephala (FMNH 57871), and since then, specimens of O. avanhandava from the upper rio Paraná have been identified as O. microcephala .

Figures

Fig. 7. Odontostilbe avanhandava: (a) holotype LIRP 3239, female, 48.7 mm SL; rio Paranaíba, Paracatu, Minas Gerais, Brazil. (b) paratype, FMNH 57871, male 62.1 mm SL, rio Tietê at Salto Avanhandava below the falls, São Paulo, Brazil; specimen reviewed by Eigenmann (1915).

Fig. 8. Dentition of Odontostilbe avanhandava, MCP 26004, paratype: (a) premaxilla, (b) maxilla, and (c) dentary, left side, lateral view. Scanning electron micrographs (SEM).

Fig. 9. (a) First gill arch of Odontostilbe avanhandava, MCP 26004, paratype, left side, lateral view. In detail (b) gill rakers on upper branchial branch, and (c) gill rakers on lower branchial branch. Scanning electron micrographs (SEM).

Fig. 6. Southern South America showing the distribution of Odontostilbe avanhandava (green diamonds), O. microcephala (yellow squares) and O. weitzmani (red circle). Type localities represented by star of respective colors.