A new Nematocharax species from the middle Contas River basin , Northeastern Brazil ( Characiformes : Characidae )

Nematocharax costai, new species is described from the Contas river basin, northeastern Brazil. The new species is included in the genus Nematocharax by possessing elongated branched dorsal-, analand pelvic-fin rays; two rows of pre-maxillary teeth in adults and practically complete row of teeth along the free ventral maxillary border. It differs from N. venustus, unique congener, by the number of maxillary teeth in adult males; absence of hooks and spinules on dorsal and pelvic fins; reduced number of anal-fin rays with spinules; presence of a long dark pink horizontal mark on caudal peduncle; number of supraneurals and pelvic-fin filament yellow. Resumo Nematocharax costai nova espécie é descrita para a bacia do rio Contas, nordeste do Brasil. A nova espécie é incluída no gênero Nema­ tocharax por possuir longos e ramificados raios nas nadadeiras dorsal, anal e pélvicas; duas fileiras de dentes pré-maxilares nos adultos e fileira praticamente completa de dentes ao longo da borda maxilar ventral livre. Ela difere de N. venustus, único congênere, pela número de dentes maxilares dos machos adultos; ausência de ganchos e espínulas nas nadadeiras dorsal e pélvicas; cinco raios da nadadeira anal com espínulas; presença de uma marca horizontal longa rosa escura sobre o pedúnculo caudal; número de supraneurais e pelo filamento amarelo na nadadeira pélvica.


Introduction
The Neotropical family Characidae is one of the most diverse fish assemblages with approximately 1200 species occurring from southern North America to the Northern Patagonia in South America (NelsoN, 2006).Despite its high species diversity, relationships between Characidae genera are still poorly known, with many insertae se dis genera (Reis et al., 2003).Recently, MiRaNde (2009, 2010) proposed a new phylogeny for the Characidae based on morphological characters corroborating the monophyly of the family.
Nematocharax is a monotypic genus of the Cha racidae, presently known only from the type locality of N. venustus WeitzMaN et al., 1986 in the Jequitinhonha River basin, southeastern Brazil.Nematocharax was diagnosed by a combination of elongate branched dorsal, anal and pelvic fin rays; two rows of premaxillary teeth in adults, and an almost complete row of teeth along the free maxillary ventral border (WeitzMaN et al., 1986).Recently, MiRaNde (2010) listed eight autapomorphies for N. venustus: presence of five or more cusps on the teeth of the outer row of premaxilla; edge of posterior extent of the ventral process of the quadrate close to posterior margin of sympletic; absence of a bony lamella dorsal to the fourth basibranchial; ventral end of the posttemporal anterior or lateral to the lateral margin of the epioccipital; four or fewer supraneurals; absence or small bony lamellae associated with supraneurals (a polymorphic character); presence of bony hooks on the dorsal fin in adult males and scales covering one third of caudal fin lobes length.
A new species herein described was recently collected in the Contas River basin, Northeastern Brazil being the second species and the further north record for the genus, formally restricted to the Jequitinhonha river basin.FiNk & WeitzMaN (1974).Measurements are presented as percentages of standard length (SL), except for subunits of head, which are presented as percentage of head length (HL).Meristics and morphometrics data are given in the tables, with information for the holotype given separately.Ranges in the tables are represented by a set of data for both sexes.In cases of sexual dimorphism data are recorded separately.Counts of dorsal and ventral limb gills rakers, radials, vertebrae, and osteological observations were made only in cleared and stained specimen (c&s) prepared according to tayloR & VaN dyke (1985).Material examined for this study is deposited in the Ichthyological Collection of the Laboratório de Sistemática e Evolução de Peixes Teleósteos, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro (UFRJ).Diagnosis.Nematocharax costai is included in Nema to charax by having the following unique combination of character states: elongated branched dorsal-, anal-and pelvic-fin rays; two rows of premaxillary teeth in adults, and an almost complete row of teeth along the free ventral maxillary border.Nematocharax costai is distinguished from N. venustus, unique congener, by: dorsaland pelvic-fins without hooks or spinules (vs.presence); five anal-fin rays with spinules (vs.more than seven rays); presence of a long dark pink horizontal mark on the caudal peduncle (vs.absence); five supraneurals (vs.four or fewer); pelvic-fin filament yellow (vs.pale rosy).

Nematocharax costai -new species
Description.Morphometric data for holotype and paratypes are given in Table 1.Body compressed, moderately deep, greatest body depth at vertical through dorsal-fin origin.Head and snout relatively deep.Dorsal profile of head convex from upper lip to until the beginning of orbit; straight after.Dorsal profile of body straight to slightly convex from dorsal-fin origin until adipose fin.Predorsal profile slightly convex in females and juveniles, sharply arched in males.Ventral profile of head and body slightly convex from lower lip to anal-fin origin; body profile along anal-fin base slightly convex to nearly straight in males, almost straight in females.Both dorsal and ventral profiles of body of caudal peduncle concave in both sexes.Jaws equal, mouth terminal and horizontal.Maxilla posteriorly extended, posterior tip of maxilla reaching vertical through anterior third of orbit.Premaxillary teeth arranged in two distinct rows (Fig. 3).Outer row with three teeth (Fig. 3); first to third teeth cusped, with one or three cusps.Inner row with five teeth, each with four to six, usually 5 cusps.Maxillary teeth 10 -13; anteriormost teeth with two to four cusps, last three teeth unicuspid.Dentary teeth 13, in single row; six anteriormost teeth larger, with four to five cusps, followed by two smaller teeth with three to five cusps.Remaining dentary five teeth considerably smaller and uni-or bicuspid (Fig. 3).
Scales cycloid, lateral line complete.Lateral series scales including lateral line scales 33 to 34.Horizontal scale rows between anal-fin and dorsal-fin origins 11 or 12. Horizontal scale rows around caudal peduncle 13 or 14.Scales covering less than one third of caudal peduncle.Scales counts are given in Table 2.
Last dorsal-fin ray not splitting in its base.First to fourth branched dorsal-fin rays filamentous and much more elongate in males than females (Table 1), rays extending posteriorly beyond caudal-fin base; in females rays occasionally reaching as far posteriorly as anterior origin of adipose fin.Branched rays two and three about the same length and both are shorter than branched rays one and four.Dorsal fin with minutes hooks or small bony spinules.Adipose fin in vertical slightly anterior to insertion of the last anal-fin ray.Posteriormost anal-fin ray splitting in its base.Anal fin with broad anterior lobe in both sexes (Fig. 1).Anal-fin rays of anterior lobe much longer in males than in females, posteriorly surpassing   beyond caudal-fin base; fifth unbranched anal-fin ray and first to sixth branched anal fin rays forming major part of anal-fin lobe; in males fifth branched anal-fin ray usually longest.Males with small bony spinules present on fifth unbranched and first to fourth branched rays, more developed in fourth branched ray (Fig. 2).Spinules small, one or two per ray segment.Spinules numerous, approximately 10 on each ray.Spinules distributed on median portion of rays.
Distal tip of pectoral fin extending beyond pelvic-fin origin in both sexes.Pelvic fin sexually dimorphic, first unbranched ray greatly lengthened in males.No hooks or spinules on pelvic fin.Principal caudal-fin rays 10/9 in all examined specimens.No hooks and spinules on caudal-fin rays.
Five supraneurals associated to bony lamellae.Fourth basibranchial with dorsal bony lamellae.Edge of posterior extent of quadrate ventral process, anterior to posterior margin of sympletic.Ventral end of posttemporal anterior or lateral to lateral margin of epioccipital.

Colouration in alcohol.
Entire body pale yellowish brown.Series of small chevron-shaped marks along middle region of body, between horizontal connection of dorsal and ventral myomeres; chevron-shaped marks especially distinct below dorsal to adipose fin.Dark brown shield-shaped spot on caudal-fin peduncle, anteriorly tapering to narrow stripe bellow adipose fin, posteriorly terminating at distal tip of five central rays of caudal-fin.The dorsal surface of body dark brown, from posterior region of head to caudal peduncle.Ventral region of flank silvery white anterior to anal-fin, light yellowish brown to caudal peduncle.Head dusky dark brown dorsally, light yellowish brown ventrally.Dark brown mark on opercle as a crescent-shape or small spot.Fins transparent in both sexes except by males dark brown dorsal-fin filamentous rays.Caudal fin dusky with pale brown chromathophores on fin rays.Anal fin dusky on ventral border.
Colouration in life.Males.(Fig. 1) Body flank silvery on ventral region; greenish gray on upper region, between head and dorsal-fin base, bright yellow posteriorly.Pale gray chevron-shaped marks, along midline region of flank, between horizontal connection of dorsal and ventral myomeres; long dark pink horizontal mark extending in a vertical through middle anal-fin base to caudal-fin base; a long and wide pale green and pink metallic stripe from the end of the head to dark pink mark; a orange blotch on sides near head; some dark brown chromatophores scattered on posterior region of caudal peduncle and base of middle caudal-fin rays.Dorsum bright yellow, just anterior to dorsal-fin base to caudal peduncle, light pink to head.Head bright yellow on dorsum, silver below eyes.Adipose fin pale yellow.Dorsal-fin first rays pale blue, central region pale pink, remaining rays slightly yellowish.Anal-fin anterior lobe slightly pink, posterior distal border pale yellow.Pelvic fin pale blue; slightly pink on base anterior region; elongated rays tips yellow.Dorsal and ventral caudal-fin lobe bright yellow distally.Silver iris with rosy dark spot dorsally.
Habitat notes.The Cambiriba is a sandy bottom fast running water stream, with about 7 m wide, 1 m deep (Fig. 4).The water was pale brown and turbid, and all specimens were found under marginal vegetation.

Etymology.
In honor to ichthyologist Wilson Costa, notably known for his great contribution in Ichthyology and for his main role in planning the expedition and first to recognize the new species in the field.