Characidium xanthopterum, Silveira & Langeani & da Graça & Pavanelli & Buckup, 2008

Silveira, Luiz G. G., Langeani, Francisco, da Graça, Weferson J., Pavanelli, Carla S. & Buckup, Paulo A., 2008, Characidium xanthopterum (Ostariophysi: Characiformes: Crenuchidae): a new species from the Central Brazilian Plateau, Neotropical Ichthyology 6 (2), pp. 169-174 : 170-172

Characidium xanthopterum , new species Figs. 1-3

Characidium sp. Pavanelli et al., 2007:60 [ Brazil, Goiás, rio Corumbá basin; check list].

Holotype. DZSJRP 10474, 47.3 mm SL, Brazil, Goiás, Mun. Caldas Novas, riacho outside of Parque Estadual de Caldas Novas, 17°46’9"S 48°39’19"W, 8 Jun 2007, team from Laboratório de Ictiologia, Departamento de Zoologia e Botânica, IBILCE/ UNESP.

Paratypes. All from Brazil, Goiás. Upper rio Paraná basin, rio Paranaíba drainage: Mun. Bela Vista de Goiás: DZSJRP 6491, 4, 34.7-36.2 mm SL, rio Corumbá , Arapuca farm, 17º4’6"S 48º43’49"W, 29 Apr 2004, D. O. Tavares et al.; DZSJRP 6508, 1, 42.2 mm SL, unnamed córrego tributary to rio Arapuca , Arapuca farm, 17º05’32"S 48º43’47"W, 29 Apr 2004, D. O. Tavares et al.; DZSJRP 6853, 2, 38.8-42.0 mm SL, rio Corumbá , Arapuca farm, 17º5’32"S 48º43’47"W, 13 Jul 2004, D. O. Tavares et al.; DZSJRP 6980, 6 + 1 cs, 32.2-44.5 mm SL, rio Corumbá , 17º5’34"S 48º43’49"W, 2 Nov 2004, D. O. Tavares et al.; DZSJRP 7041, 1, 35.2 mm SL, rio Corumbá , GO-020 highway, Km 78, 17º4’7"S 48º43’59"W, 6 Feb 2005, D. O. Tavares et al.; DZSJRP 7060, 4 + 1 cs, 30.4-36.1 mm SL, rio Corumbá , GO-020 highway, Km 78, 17º5’33"S 48º43’47"W, 7 Feb 2005, D. O. Tavares et al. Mun. Caldas Novas: DZSJRP 10797, 1, 44.9 mm SL, collected with the holotype. [Mun. Coromandel]: MNRJ 11481 , 20 , 19.6-33.1 mm SL, unnamed córrego tributary to rio Verde , on the downhill road towards the rio Verde (mouth of rio Verde is located at 18º3’33"S 47º16’59"W), 28 Apr 1986, G. W. Nunan & D. F. Moraes Jr. Mun. Catalão: MNRJ 19729 , 1 , 45.1 mm SL, córrego Taquari, a left bank tributary to rio São Marcos , 17º43’5"S 47º34’25"W, 25 Sep 1999, C. A. Figueiredo et al.; MNRJ 19842 , 2 , 38.6-47.1 mm SL, córrego Prata, a right bank tributary to rio São Marcos , 17º47’24"S 47º35’46"W, 21 Sep 1999, F. A. Bockmann et al. Mun. Mineiros: MNRJ 20256 , 7 , 28.7-33.1 mm SL, and MNRJ 20257 , 6 , 36.1-39.1 mm SL, córrego Coqueiros, BR-364, 17º30’25"S 52º32’18"W, 12 Nov 2000, F. A. G. Melo et al. Mun. Corumbaíba: NUP 4414 , 15 , 32.8-40.4 mm SL, and NUP 4415 , 2 cs, 37.6-42.0 mm SL, córrego Gameleira, tributary to left margin of rio Corumbá , 17º59’S 48º29’W, 12 Oct 1996, Nupélia .

Additional examined specimens. All from Brazil, Goiás, upper Tocantins basin: Mun. Niquelândia: MNRJ 11540 , 21 , 27.4-35.6 mm SL, riacho do Padre , right bank tributary to rio Tocantinzinho , 14º8’30"S 48º05’W, 11 Oct 1985 ; MNRJ 11542 , 3 , 26.0- 30.7 mm SL, 14º18’S 48º7’30"W, 11 Oct 1985 . Mun. São João do Castelão: MNRJ 13288 , 35 , 13.1 -24.0 mm SL, calcareous sink (dolina) of a tributary to rio Castelo Grande , a right bank tributary to rio Maranhão, 11 Oct 1985 . Mun. Minaçu: MZUSP 53404 , 20 , 30.5- 39.9 mm SL, unnamed córrego tributary to rio Tocantinzinho , 14º2’12"S 48º13’22"W, 19 Dec 1995 . MZUSP 53422 , 3 , 37.4-43.1 mm SL, tributary to rio Tocantinzinho , 14º2’27"S 48º12’22"W, 20 Dec 1995 .

Diagnosis. Characidium xanthopterum is diagnosed among congeners by the bright yellow fin coloration, and by the absence of conspicuous dark bars along the sides of body in individuals larger than 35 mm SL (vs dark bars or marks present on the sides of the body in specimens of all sizes in the remaining species of Characidium ).

Description. Based on specimens from upper rio Paraná basin. Morphometric data in Table 1. A medium-sized Characidium , largest specimen examined 47.3 mm SL. Body compressed. Dorsal profile convex between anterior tip of snout and dorsal-fin origin, except for small concavity at supraoccipital process, almost straight between bases of dorsal and caudal fins. Ventral profile convex from lower lip to pelvic-fin insertion, straight between pelvic-fin insertion and anal-fin origin, slightly concave from anal-fin origin to caudal-fin base.

Snout rounded in dorsal view, its tip aligned with ventral margin of orbit.Mouth small, terminal; maxilla moderately elongate, reaching vertical line through anterior third of orbit. Orbit slightly larger than snout length. Cheek shallow, its depth about half of orbit diameter. Nares distinctly separated; posterior naris closer to eye than to anterior naris; margin of anterior naris raised, forming circular rim, without dermal flaps; posterior naris directed backwards, with rim raised and not forming dermal flaps.

At least 1-2 medial lower-jaw teeth tricuspid. Dentary teeth in single series, 8/8(1), 9/9(1) or 10/8(1), decreasing gradually in size from symphysis towards lateral posterior portion of dentary. Premaxillary teeth 6/6(1), 7/7(1) or 8/8(1), mostly unicuspid, occasionally with very small lateral cusps on medialmost teeth, decreasing gradually in size from symphysis towards lateral posterior portion of premaxillary. Maxillary teeth absent. Ectopterygoid conical teeth in a single series of 11/11, 10/13 or 14/14. Mesopterygoid teeth absent.

Branchiostegal rays 4/4(2) or 4/5(1); 3 or 4 at anterior ceratohyal, 1 at posterior ceratohyal. Supraorbital present, somewhat triangular in dorsal view, with anterior margin wider than posterior one; medial margin slightly concave, abutting frontal. Parietal branch of supraorbital canal present, extending through almost two thirds of parietal. Parietal fontanel limited anteriorly by frontals.

Orbitosphenoid slightly rectangular in lateral view, connected anteriorly to rhinosphenoid, with free posterior-ventral margin concave. Pterosphenoid foramen for ophthalmic nerve relatively small, formed by tunnel crossing pterosphenoid diagonally, bordered ventrally by bony crest that conceals the brain cavity from lateral view.

Scales cycloid; about 10-12 radii on posterior field of scale located immediately below 10 th scale of lateral line. Lateral line complete, with 32(15), 33(7), 34(38*), 35(2) or 36(4) perforated scales. Scale rows above lateral line 3(51), 4(14*); scale rows below lateral line 3(63*). Scale rows around caudal peduncle 10(5), 12(59*). Scales in regular predorsal series 8(2), 9(20), 10(23*), 11(10). Scales from base of dorsal fin to origin of adipose fin 7(6), 8(15*), 9(29), 10(7). Isthmus completely covered with scales. Pseudotympanum present, represented by muscle hiatus at vertical through anterior portion of swim bladder between first and second pleural ribs.

Dorsal-fin rays ii,8(4), ii,9(36*) or ii,10(22). Adipose fin present. Pectoral-fin rays iii,8(31), iii,9(33*) or iii,10(1), in some specimens reaching pelvic-fin origin. Pelvic-fin i,8(65*), in some specimens reaching anal-fin origin. Anal-fin rays, ii,6(54*) or ii,7(9); fin elements (i.e., adnate rays) on last pterygiophore 2(58*), counted as single ray in total count. Principal caudal-fin rays 9(3), 10(42*), 11(1) on dorsal lobe, 9(42*) on ventral lobe. Mature males with at least five welldeveloped sexual hooks on dorsal surface of first five branched and unbranched pectoral and pelvic fin-rays; some with hooks only on pelvic fins. Only one hook per ray-segment, usually absent on the first proximal identifiable segment.

Total number of vertebrae 32(1), 33(2). Swim bladder well developed, extending through entire length of visceral cavity. Supraneural bones 5(2), 6(1), anterior to neural spine of fifth or sixth centrum. Epural bones 2(2), 3(1). Single pair of uroneural bones present (3).

Color in alcohol. Ground color of head and body brownpurple. Opercular bones and pectoral girdle pale yellow. Chromatophores distributed over entire surface of head, sparse at gular area; dorsal portion of head and body dark, lighter ventrally. All scales, except ventral ones, with chromatophores concentrated at their posterior margin, forming checkered pattern. Adult specimens with brown, dark and pale yellow pigmentation, uniformly checkered, except for inconspicuous midlateral longitudinal stripe, positioned slightly above lateral line. Dark humeral blotch usually conspicuous, vertically elongate. Dark, oblique stripe extending from upper lip to anterior margin of orbit. Black spot slightly vertically expanded near base of middle caudal-fin rays inconspicuous or absent. All fins pale yellow. Specimens smaller than 32 mm SL with eight to 11 vertical bars on sides of body, shaped as inverted isosceles triangles, darker on dorsal portion; humeral blotch partially merged into first bar; black, thin stripe present; dark spot present at base of middle caudal-fin rays. Fins hyaline, with scattered chromatophores along rays ( Fig. 2).

Color in freshly preserved specimens. Body almost entirely brown-reddish; cheek, opercular region, and lateral portion of pectoral girdle yellow; fin rays bright yellow. Dorsal portion of head, opercle, and humeral blotch conspicuously dark. Inconspicuous, narrow midlateral longitudinal stripe, running slightly above lateral line, from humeral blotch to caudal peduncle.

Sexual dimorphism. Mature males with sexual hooks on unbranched and branched rays of pectoral and pelvic fins (most evident in MNRJ 11481). Small, inconspicuous hooks observed on pelvic-fin rays of immature males.

Geographic variation. The description above is based on specimens from the upper rio Paraná basin. To provide comparative morphometric data, specimens from the upper rio Tocantins basin were also measured (Additional examined specimens; Table 1). These specimens differ in the number of scale rows around the caudal peduncle (12 or 14, mode=14 vs 10 or 12, mode= 12 in specimens from the upper Paraná basin) and deeper cheek (7.1-10.1, mean= 8.3 vs 10.4-19.8, mean=15.1% of head length in specimens from the upper rio Paraná basin). Due to the overlap and individual variation of meristic data between the samples from these two river drainages, the upper Tocantins population is not considered a different species.

Distribution and habitat. Characidium xanthopterum is known from tributaries of the rio Paranaíba drainage, upper rio Paraná basin, and tributaries to the upper rio Tocantins basin in the State of Goiás, Brazil ( Fig. 3 ). Most specimens were collected in habitats with riffles, rocky bed with pebbles, and sand deposits.

Etymology. From the Greek xanthos (yellow) and pteron (fin) meaning yellow fin, in a reference to the bright yellow fins of living specimens. An adjective.

Figures

Fig. 1. Characidium xanthopterum, holotype, DZSJRP 10474, 47.3 mm SL, freshly preserved specimen.

Fig. 3. Map of central Brazil, showing distribution of Characidium xanthopterum. Arrow indicates type-locality (Caldas Novas, Goiás State, upper rio Paraná basin), complete circles represent localities in the upper rio Paraná basin, and open circles represent localities in the upper rio Tocantins basin. Symbols may represent more than one lot or locality.