Odontostilbe weitzmani, 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 : 3-8

Odontostilbe weitzmani , new species

urn:lsid:zoobank.org:act:B3D5A4C7-DF4C-482A-83B9-0147BE3C60FE

Figs. 1-5

Odontostilbe microcephala non Eigenmann, 1907. - Eigenmann, 1915 [in part]: 94-95 [three smaller specimens from CM 6854ac (FMNH 131317, 35.9-38.8 mm SL) and ten specimens from CM 6855 (CAS 60508, 3, 25.0- 39.4 mm SL) and FMNH 57872 (7, 21.4-23.9 mm SL)] from rio Tietê at Salto Avanhandava above the falls, São Paulo, upper rio Paraná basin]. - Uj, 1987: 132 (key), 138 (description), 154 (osteological description of skull, dorsal and anal fins, generic position), 160 (distribution).

Odontostilbe sp. - Santos et al., 2017: e20160196, 4, fig. 3(t) [checklist].

Holotype. MZUSP 121648 , 42.5 mm SL, Itirapina, São Paulo State. Lapa stream near the mouth and along the seawall of rock and the bridge on the road , 22°22′ 35.5″ S 47°46′55.6″W, 31 Jan 2002, E. N. Fragoso.

Paratypes. All from Brazil, upper rio Paraná basin. São Paulo State: CAS 60508, 3, 25.0- 39.4 mm SL, rio Tietê at Salto Avanhandava below the falls, São Paulo, 21°10′3.5″ S 50°7′3.22″W, 14 Sep 1908, J. D. Haseman. FMNH 131317 , 3 , 35.9-38.8 mm SL, rio Tietê at Salto Avanhandava below the falls 21°10′03″S 50°7′03″W, 15 Sep 1908, J. D. Haseman. FMNH 57872 , 7 , 21.4-23.9 mm SL, rio Tietê at Salto Avanhandava below the falls, São Paulo, 21°10′03″S 50°7′03″W, 15 Sep 1908, J. D. Haseman. MCP 32277, 2 , 37.9-42.3 mm SL, rio Piracicaba , Piracicaba , tributary of rio Tietê , 22°43′19″S 47°39′21″ W, 29 Jan 2001, C. Lucena, J. Silva, E. Pereira & A. Cardoso. MCP 12108, 2 , 42.3-43.8 mm SL, Ilha Solteira , rio Paraná , W, 19 Oct 1969, Expedition Department of Zoology USP leg. MZUSP 42657 , 186 , 33.3-43.4 mm SL, rio Mogi Guaçu , Emas, Pirassununga, 21°55′00″S 47°23′00″W, EEBP-Emas. MZUSP 16851 , 13 , 36.8-41.8 mm SL, rio Mogi Guaçu , Emas, Pirassununga, 21°55′00″S 47°23′00″W, 22 Oct 1963, H. A. Britski. MZUSP 87947 , 10 , 42.5-50.5 mm SL, Itirapina, stream of Lapa near the mouth and along the seawall of rock and the bridge on the road, 22°15′00″S 47°51′48″ W, 31 Jan 2002, E. N. Fragoso. Mato Grosso do Sul State: MCP 12105, 2 , 34.2-37.2 mm SL, rio Paraná , in front of Jupiá, Três Lagoas, 11-13 Oct 1969, Expedition Department of Zoology USP leg. MZUSP 4011 , 2199 , 25.3 -40.0 mm SL, rio Paraná , in front of Jupiá, Três Lagoas, 21°07′10″S 51°45′00″W, 4 Dec 1960, P. E. Vanzolini & S. Saiar. Goiás State: MCP 27814, 9 , 39.5-50.8 mm SL, rio São Marcos , road Catalão / Davinópolis, Catalão, 18°06′15″S 47°41′35″W, 23 Jan 2001, C. Lucena, J. Silva, E. Pereira & A. Cardoso. MCP 26001, 1 , 40.3 mm SL, rio Corumbá , downstream UHE Corumbá, rio Paranaíba , Caldas Novas, 17°29′00″S 48°23′00″W, 15 Oct 1996, Nupelia. MCP 20337, 50 , 36.8 - 54.2 , rio Corumbá , affluent of rio Paranaíba. region of the municipalities of Caldas Novas , Corumbaína , Pires do Rio and Ipameri , 18°00′00″S 49°00′00″W, 07 Sep 1996, Nupelia.

Non types. All from Brazil, upper rio Paraná basin. Goiás State: MCP 25999, 2, 56.1-56.3 mm SL, rio Corumbá, near the mouth of rio Pirapitinga, (tributary of rio Paranaíba), 17°47′00″S 48°32′60″ W, 18 Sep 1996, Nupelia. MCP 26000, 2, 55.1-56. 8 mm SL, rio Corumbá, near the mouth of rio do Peixe (tributary of rio Paranaíba), 17°36′00″S 48°27′00″W, 21 Sep 1996, Nupelia .

Diagnosis. Odontostilbe weitzmani differs from all species of the genus, except from Odontostilbe avanhandava , by the presence of mesopterygoid teeth, grouped on median portion of the bone, forming a continuous row (vs. absent). Odontostilbe weitzmani is distinguished from O. avanhandava by premaxillary teeth with 5(13) or 7(3) cusps [usually 5], with central cusp wider and larger than lateral cusps (vs. premaxillary teeth bearing 7-11 [usually 9] cusps, all approximately with the same size), and by the presence of 20-21 lamellae in left and right sides of central median raphe of olfactory rosette (vs. 11-12). Additionally O. weitzmani is distinguished from O. dierythrura , O. euspilurus , and O. microcephala by the terminal mouth (vs. subterminal mouth); from O. pulchra and O. ecuadorensis by the presence of hooks on first to seventh, [mostly fifth to sixth] branched anal-fin rays of males (vs. hooks on first to 22 nd branched anal-fin rays of males in O. pulchra , first to sixteenth in O. ecuadorensis ); from O. splendida by the origin of adipose fin positioned at vertical through last anal-fin ray insertion (vs. origin of adipose fin, at vertical through last 2 or 3 anal-fin rays insertion); from O. pao and O. parecis by the presence of 5-7 [mostly 5] cusps in premaxillary teeth (vs. 8-10 cusps in O. pao and O. parecis ); from O. pequira by anterior dentary teeth with 5 cusps, being central cusp larger and longer than lateral cusps (vs. dentary with 4 anterior teeth with 3 large and equally longer compressed cusps and 2-3 lateral small cusps); and from O. paraguayensis by lacking fusion of supraneurals (vs. fusion of supraneurals, wich are projected dorsal to musculature and skin of dorsum).

Description. Morphometric data on Tab. 1 . Body elongate and slightly compressed ( Fig. 1 ). Greatest body depth at vertical through dorsal-fin origin. Snout slightly elongated and round. Dorsal profile of head convex from snout to vertical through anterior bony orbital margin, slightly concave from that point to distal tip of supraoccipital bone. Predorsal profile slightly convex from posterior end of supraoccipital to dorsal-fin origin. Dorsal-fin origin located anteriorly at midlength of SL. Body profile in base of dorsal fin straight to slightly convex and slightly convex from there to origin of adipose fin. Body profile between adipose-fin base and first rays of caudal fin slightly concave. Ventral profile of head slightly convex from snout to origin of pelvic fins and slightly convex from there to origin of anal fin. Body profile along base of anal fin straight or slightly convex. Ventral profile of caudal peduncle straight to slightly concave. Caudal peduncle slightly longer than deep.

Head small relative to body length, 22.8-27.7% SL. Mouth terminal, and opening below horizontal line through middle of eye pupil. Upper and lower jaws with approximately same length. Maxilla short, posteroventrally angled, posterior tip surpassing vertical through anterior border of eye and surpassing horizontal through ventral border of eye. Teeth pedunculated distally expanded, all similar in shape. Premaxilla with 5 teeth aligned in a single row, with 5(13) or 7(3) cusps [mostly 5]. Maxilla with 2 teeth bearing 5(7) cusps. Dentary teeth with 9 gradually decreasing in size posteriorly; anterior 6, larger, bearing 5-7 cusps; followed posteriorly by smaller teeth with 1-3 cusps ( Fig. 2 ). All jaw teeth with central cup larger and wider than lateral cusps. Ventral surface of mesopterygoid with 18-19 teeth with 1-3 cusps grouped on median portion forming a continuous row ( Fig. 3 ).

Dorsal-fin rays ii, 9(60). First unbranched dorsal-fin ray about half-length of second unbranched dorsal-fin ray; branched rays gradually decreasing in size posteriorly. Dorsal fin with 10(5) pterygiophores. Presence of small ossification associated with first proximal dorsal-fin radial (character 124, described by Zanata, Vari, 2005). Proximal radial of first pterygiophore of dorsal fin posterior to neural spine of ninth precaudal vertebra. Medial radial fused with distal radial from first to fourth pterygiophores; as separate bony elements from fifth to tenth pterygiophores. Proximal radial of first to ninth pterygiophore with lateral projections, absent in tenth dorsal pterygiophore.

Adipose-fin origin posterior to vertical through base of last anal-fin ray. Unbranched anal-fin rays v(3); branched anal-fin rays 17(3), 18(20), 19(30), or 20(6) with 1 row of scales on base of anterior anal-fin rays. Profile of distal margin of anal fin distinctively concave forming an angle in tenth branched ray. Anal fin with 18(1), 20(3), or 21(1) pterygiophores. Medial radial fused with distal radial in first to sixth pterygiophore and no fused on remaining pterygiophores. Proximal radial of first pterygiophore in contact with hemal spine of first caudal vertebra.

Pectoral fin i(59), 11(22), 12(30), or 13(7). Tip of extended pectoral fin not reaching pelvic-fin origin. Pelvicfin origin anterior to vertical through dorsal-fin origin. Pelvic-fin rays i, 7(60). Principal caudal-fin rays 19(58). Dorsal procurrent caudal-fin rays 8(7), 9(2), 11(8), or 12(1) and ventral procurrent caudal-fin rays 7(2), 8(5), 9(15), or 10(4).

Cycloid scales; lateral line complete with 34(22), 35(18), 36(4), or 37(2) pored scales. Pre-dorsal scales in regular series with 10(2), 11(2), 12(30), 13(17) or 14(3) scales; scale rows between lateral line and dorsal line origin 5(51); scale rows between lateral line and pelvic-fin origin 3(9) or 4(42); circumpeduncular scale rows 14(14).

Supraneurals 4(3) without anterior and posterior projections, 5(3) upper gill rakers and 10(3) lower gill rakers (2 on hypobranchial). Upper gill rakers with 2-5 denticles on anterolateral border, and 0-2 on posterolateral border, mainly on basal portion of upper gill rakers. Lower gill rakers with 3 or 6 denticles on anterolateral border, and none on posterolateral border. Gill raker at junction of ceratobranchial and epibranchial with 3-4 denticles on dorsolateral and 3 on ventrolateral borders ( Fig. 4 ). Olfactory rosette slightly oval with 20(2) or 21(1) lamellae in left and right sides of central median raphe. Precaudal vertebrae 16(3); caudal vertebrae 18(3); total vertebrae 34(3).

Color in alcohol. Overall body coloration yellowish. Dorsal surface of head from snout to posterior limit of frontal darker with scattered light grey chromatophores. Darker in region of parietal and supraoccipital. Opercular apparatus and infraorbital region of beige silver color extending to cleithrum. 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. Scales of dorsal portion of body from supraoccipital to caudal peduncle with small dots dim-gray concentrated in posterior margin.Posterior region of pseudotympanum to caudal peduncle with a silvery lateral thin band above lateral line, top edge of chromatophores dim-gray forming a dark band reaching caudal spot. A conspicuous horizontally oval black caudal spot continued on base of middle caudal-fin rays ( Fig. 1 ).

Dorsal fin with scattered black chromatophores slightly darker and more numerous on mid-distal portion of dorsal fin, extending from second unbranched to eighth branched dorsal-fin rays. Pectoral and pelvic fins with dark grey chromatophores scattered mainly in unbranched rays. Anal fin with dark grey dots slightly scattered in all rays, concentrated in basal region. Adipose fin unpigmented.

Color in life. Caudal spot black, not reaching upper and lower margin of caudal peduncle and extending to base of central rays of caudal-fin, followed by silvery pigments in each lobe. Basal part of anal fin gold silvery. Body silvery, with scattered dark chromatophores on scales and fins ( Fig. 5 ).

Sexual dimorphism. Mature males have second unbranched ray of dorsal fin and unbranched ray of pelvic fin slightly longer than remaining rays, differing from immature and females. Mature males with small hooks on pelvic and anal–fins rays. Pelvic–fin with small hooks in all branched rays, with 1 retrorse bony hook per segment on medioventral border of both lepidotrichia in median and distal length of pelvic-fin rays. 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 arranged (exceptionally two pairs of hooks), present from last unbranched ray to fourth or seventh branched rays, decreasing in number posteriorly. Hooks mostly distributed along middle third of anal-fin ray length in posterolateral border. Distal tip of bony hooks not reaching proximal border of segment of lepidotrichia where inserted.

Males bearing gill gland ( Fig. 4 ) similar in size and number of modified filaments (8) to those observed in other externally fertilized species of Cheirodontinae ( Oliveira et al., 2012) .

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

Etymology. The specific epithet is named after Stanley H. Weitzman, in recognition for his work on the systematics of Neotropical characiforms, particularly of the characid subfamily Cheirodontinae .

Conservation status. Odontostilbe weitzmani is abundant where it occurs. This species may be categorized as Least Concern (LC), according to the IUCN criteria for evaluation on threatening status, version 13 (IUCN, 2017).

Remarks. Besides the type specimens from the upper rio Paraná basin, on which we based the description, we analyzed additional lots of Odontostilbe weitzmani from two localities along the rio Corumbá, Goiás (MCP 25999 and MCP 26000- female, 55.1-56.8 mm SL). These specimens have the same number of cusps on premaxillary teeth, number of branched anal-fin rays and other morphometric characters as the type specimens, but can be differentiated in the length of caudal peduncle (9.9-11.8% SL, mean 10.6% SL vs. 10.8-14.5% SL, mean 12.5% SL in O. weitzmani type specimens) and body depth at dorsal-fin (35.0-37.1% SL, mean 36.0, vs. 23.1-32.9% SL, mean 27.9% SL in O. weitzmani type specimens). We suggest that this difference is related to the larger size of the individuals from rio Corumbá. Stretches of the rivers where these specimens were collected have been changed from lotic to lentic environments by the construction of hydroelectric power dams, and this may possibly influence the body size, body depth and caudal peduncle length of studied populations.

Several specimens of Odontostilbe weitzmani collected in the upper rio Paraná basin are found among the material that Eigenmann (1915) used to redescribe Odontostilbe microcephala ( Fig. 1c ; CM 6854a-c, now FMNH 131317; CM 6855a-p, now CAS 60508 and FMNH 57872), and since then, specimens of O. weitzmani from the upper rio Paraná have been erroneously identified as O. microcephala .

Figures

Fig. 1. Odontostilbe weitzmani: (a) holotype, MZUSP 121648, 1, 42.5 mm SL, Itirapina, São Paulo State. (b) paratype, MCP 32277, female, 42.2 mm SL, rio Piracicaba, São Paulo. (c) paratype, FMNH 131317, female, 38.7 mm SL, rio Tietê at Salto Avanhandava below the falls, São Paulo, Brazil. FMNH 131317 was listed under O. microcephala by Eigenmann (1915).

Fig. 2. Dentition of Odontostilbe weitzmani, paratype MCP 20337 male: (a) left side premaxilla, (b) maxilla, and (c) dentary, lateral view. Scanning electron micrographs (SEM).

Fig. 3. Mesopterygoid of Odontostilbe weitzmani paratype, male (MCP 20337) ventral view: (a) mesopterygoid with teeth forming a row, (b) detailed image of the teeth of mesopterygoid with 1, 2 and 3 cusps. Scanning electron micrographs (SEM).

Fig. 4. Live specimen of Odontostilbe weitzmani collected in the Municipality of Carmo do Rio Claro, stream tributary of Ribeirão Itaci, rio Grande, upper rio Paraná, Minas Gerais, Brazil (not preserved, photo by Azevedo-Santos, V. M.).

Fig. 5. First gill arch of Odontostilbe weitzmani: (a) left side, lateral view, showing gill gland (arrow) on anteriormost portion of lower branch of MCP 20337 male. In detail (b) gill rakers near the junction of ceratobranchial and epibranchial, and (c) gill rakers on lower branch of gill arch. 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.