Trichomycterus payaya, new catfish (Siluriformes: Trichomycteridae) from headwaters of rio Itapicuru, Bahia, Brazil

Trichomycterus payaya, new species, is described from tributaries to the upper rio Itapicuru basin, northern Bahia State, Brazil. The new species is distinguished from congeners by having the head rounded anteriorly in dorsal view and slightly depressed in lateral view, supraorbital pores s6 paired, opening laterally on the supraorbital sensory branch, not emerging from an epiphyseal branch, lateral process of the urohyal distally sharp and with pointed tip, interopercular patch of odontodes longer than deep, with 21-26 odontodes, small number of pleural ribs (5-6 ribs), and dorsal fin in a posterior position. This is the first record of a Trichomycterus from the semiarid region of northeastern Brazil.


Introduction
Fishes of the freshwater family Trichomycteridae form a well corroborated monophyletic assemblage and a particularly diverse group, with more than 200 species, spread throughout South and part of Central America (de Pinna & Wosiacki, 2003). Among the eight recognized subfamilies in Trichomycteridae, the most problematic is Trichomycterinae, an apparently non-monophyletic assemblage diagnosed basically by the lack of specializations of the other subfamilies (Baskin, 1973;de Pinna, 1989;de Pinna, 1998;de Pinna & Wosiacki, 2003). Trichomycterus is the most specious genus within the subfamily, with more than 120 nominal species, and represents one of the most widely distributed Neotropical siluriform groups, inhabiting lowlands to the high Andes, thermal waters to cold rivers, and epigean to subterranean habitats (e.g., Fernandez & Miranda, 2007;Trajano et al., 2009). Most species have a limited distribution and display a high level of endemism (Eigenmann, 1918;Costa, 1992;Bockmann & Sazima, 2004). The diverse group is currently undiagnosable by synapomorphies (Wosiacki & de Pinna, 2008a).

Material and Methods
Straight-line measurements were taken under a stereomicroscope with a digital caliper, and recorded in tenths of a millimeter. Methodology and terminology for measurements followed Tchernavin (1944), de Pinna (1992, and Trajano & de Pinna (1996). Standard length (SL) is expressed in mm. In order to check the position of the dorsal fin in the species examined we used the proportional distance PDL/DFC adapted from Triques & Vono (2004) whereby PDL is predorsal length and DFC is the distance from the dorsalfin origin to the base of the middle caudal-fin rays. Measurements of pectoral-fin filament were checked in specimens greater than 30 mm SL. Meristic data were obtained from alcoholic and cleared and stained (c&s) specimens. Holotype meristics indicated by asterisk when variation occurs. Fin-rays were counted under a stereomicroscope. Dorsal-and anal-fin ray counts include the two unbranched rays, visible when back lighted, and subsequent branched rays; pectoral-and pelvic-fin rays include the first unbranched plus branched rays. Vertebral counts follow de Pinna (1992). Branchiostegal rays and rib counts were verified on c&s specimens and upon dissection of some alcoholic specimens. Osteological examination was based on c&s specimens according to the procedures of Taylor & van Dyke (1985). Terminology and nomenclature for osteological data followed Arratia & Huaquin (1995) and Arratia (2003). Morphological information about Scleronema operculatum and T. nigricans were based on digital photographic images and radiographs. Specimens examined via photographic images (I) or radiographs (R) are indicated in Comparative material section. Morphological data for T. auroguttatus, T. brunoi, T. claudiae, T. concolor, T. fuliginosus, T. giganteus, T. itacarambiensis, T. landinga, T. macrotrichopterus, T. mariamole, T. mimonha, T. nigroauratus, T. novalimensis, T. potchi, T. rubiginosus, T. trefauti, and T. vermiculatus were based on literature accounts (Costa, 1992;Trajano & de Pinna, 1996;Barbosa & Costa, 2003, 2008Bockmann & Sazima, 2004;Lima & Costa, 2004;Triques & Vono, 2004;Wosiacki, 2005;Lima et al., 2008)

Diagnosis.
Trichomycterus payaya is distinguished from all congeners by a unique combination of features: head rounded anteriorly in dorsal view and slightly depressed in lateral view; supraorbital pores s6 paired, opening laterally on supraorbital sensory branch, not emerging from an epiphyseal branch; lateral process of urohyal distally sharp, with pointed tip; reduced number of pleural ribs (5-6 ribs); and interopercular patch of odontodes longer than deep, with 21-26 odontodes. Trichomycterus payaya can be further distinguished from all congeners inhabiting the Brazilian coastal rivers located north of rio Paraíba do Sul (T. alternatus, T. bahianus, T. brunoi, T. caudofasciatus, T. itacambirussu, T. jequitinhonhae, T. landinga, T. longibarbatus, T. pantherinus, T. pradensis) by having the dorsal fin positioned somewhat posteriorly, the distance from the dorsal-fin origin to the base of the middle caudal-fin rays 1.9-2.2 in predorsal distance (vs. 1.4-1.8 in predorsal distance).
The new species differs further from congeners of northeastern Brazilian drainages (T. bahianus, T. itacambirussu, T. jequitinhonhae, T. landinga, T. pradensis) by having a large opercular odontode patch with 16-19 odontodes (vs. small odontode patch with 8-13 odontodes). It differs further from T. bahianus, T. itacambirussu, and T. jequitinhonhae by having body coloration somewhat homogeneous, with minute spots distributed throughout (vs. presence of rounded dark brown or gray spots sometimes arranged into series along body), from T. landinga by having dorsal and ventral flanks similarly colored (vs. dorsal flank finely dotted and ventral flank with dark dots scarce), and from T. pradensis and T. itacambirussu by having six branched pectoral-fin rays (vs. eight or nine). Trichomycterus payaya can be also distinguished from its congeners of the rio São Francisco drainage (T. brasiliensis, T. concolor, T. macrotrichopterus, T. novalimensis, T. reinhardti, T. rubiginosus, T. trefauti, T. variegatus) by having a narrower caudal peduncle (7.5-9.6% vs. 10.5-13% of SL) and longer nasal barbel (14.2-15.9% vs. 8.4-12.9% of SL). See discussion for details on other distinguishing features. Table 1. Body slim, trunk compressed, caudal peduncle laterally compressed. Dorsal profile of body gradually ascending from tip of snout to anterior portion of trunk, approximately straight from that point to base of dorsal fin, descending along dorsalfin base and straight on caudal peduncle until caudal fin. Ventral profile of head gently sloped. Ventral profile of body almost straight to shallowly convex.

Description. Morphometric and meristic data presented in
Head rounded anteriorly in dorsal view, small, and slightly depressed. Eyes small, orbital margin not free; thin skin covering eye. Anterior nostril surrounded by fleshy, tubeshaped flap of integument. Posterior nostril surrounded anteriorly by raised fleshy flap and located slightly closer to anterior nostrils than to eye. Mouth subterminal; lower lip contoured by fleshy lobe medial to origin of rictal barbels; upper lip with fleshy fold limited to base of maxillary barbel. Nasal barbel originating on lateral portion of integumentary flap around anterior nostril; tip of barbel reaching opercular odontode patch. Maxillary barbel reaching pectoral-fin origin. Rictal barbel extending to interopercular odontode patch. Autopalatine large, posteriorly expanded with wide lateral projection. Jaws subequal; premaxilla and dentary almost straight with two or rarely three rows of conical teeth. Premaxilla narrow, transversely elongated, meeting its counterpart medially. Maxilla well developed and curved. Branchial membranes thick, united to isthmus only anteriorly.
Anterior portion of Weberian complex fused to basioccipital-exoccipital. Suspensorium with robust hyomandibula, projected anteriorly as membranous outgrowth. Laminar projection of hyomandibula anteriorly sutured to quadrate only, not contacting metapterygoid. Metapterygoid short, laminar, almost rectangular, joined to quadrate via anterior cartilage block only. Quadrate elongate, with broad base and anterior laminar projection contacting both hyomandibula and metapterygoid. Quadrate and hyomandibula contacted also through their broad bases and cartilaginous joint. Short preopercle sutured to ventral margins of both quadrate and hyomandibula. Opercular patch of odontodes large and roundish. Opercle with 16-19* elongate odontodes, posterior ones longest. Interopercular patch of odontodes longer than deep, with short anterior process. Interopercle with 21-26* odontodes arranged into two or three irregular rows (Fig. 4).
Hyoid arch with large ventral hypohyal, elongate anterior ceratohyal and somewhat triangular posterior ceratohyal with markedly concave posterior face and with articulatory surface for interopercle and ligamentous connection to suspensorium. Seven branchiostegal rays articulated with hyoid arch: three with anterior ceratohyal, one with interceratohyal cartilage between bones, and three with posterior ceratohyal. Brachiostegal rays 4-6, distally expanded and notched. Dorsal hypohyal and interhyal absent. Urohyal wide, bearing conspicuous foramen. Anterior head of urohyal expanded, lateral processes elongated, laminar, sharpened distally to pointed tip. Posterior process of urohyal moderately short and sharpened (Fig. 5).
Basibranchial 1 absent; basibranchial 2 and 3 with cartilaginous anterior and posterior tips, connected to each other, forming osseous rod. Anterior cartilaginous tip of basibranchial axis reaching close to hypobranchial 1; posterior osseous tips nearly in contact with contralateral hypobranchial 3. Cartilage between basibranchial 2 and 3 bordered laterally by cartilaginous head of hypobranchial 2. Basibranchial 4 hexagonal and completely cartilaginous, bordered anteriorly by cartilaginous head of ceratobranchial 4 and posteriorly by cartilaginous head of ceratobranchial 5. Hypobranchial 1 osseous, rod like, with cartilage on its proximal and distal tips. Hypobranchial 2 elongate, cartilaginous, almost trapezoid, with osseous anterodistal process. Hypobranchial 3 approximately trapezoidal, mostly cartilaginous and positioned close to its counterpart. Hypobranchial 4 absent. Five ceratobranchials, mostly ossified, extremities cartilaginous. First ceratobranchial short, supporting diminutive rakers. Second and third ceratobranchials each with shallow cavity along posterior margin and mesial laminar extension. Fourth ceratobranchial with diminutive concavity. Fifth ceratobranchial with short proximal tip, slightly expanded posteromedially to support lower pharyngeal tooth plate. Tooth plate with fine conical teeth arranged in two rows, with about seven teeth in mesial row. Five epibranchials, first three-rod like, short, ossified, except for cartilaginous extremities. Posterior margin of epibranchial 1 with elongate anterior process. Epibranchial 2 with vestigial process on its anterior margin. Epibranchial 3 with elongate posterior uncinate process. Epibranchial 4 broad, somewhat rectangular, without processes. Epibranchial 5 very small, completely cartilaginous, placed between posterior cartilaginous tips of epibranchial 4 and ceratobranchial 4. Pharyngobranchials 1 and 2 absent. Pharyngobranchial 3 elongate, ossified, rod-like, with  (Fig. 6). Cephalic sensory canals enclosed in bone, with some branches deeply embedded. Head sensory canals with simple tubes, each ending in single pore. All canals continuous and connected to each other. Supraorbital sensory canal running along frontal and nasal bones, giving off three paired pores: pore s1 placed between palatine and mesethmoid, pore s3 between anterior margin of frontal and vomer, and pore s6 on frontal, close to lateral border. Pores s1 and s3 placed between anterior margin of frontal and vomer. Pore s6 opening laterally on supraorbital sensory branch, not emerging from epiphyseal branch. Supraorbital canal joining infraorbital canal on anterior part of sphenotic. Infraorbital canal incomplete, running along head surface, giving off two branches, anterior one with pores i1 and i3, connected by single canal, both close to lacrimal, anteriorly to eye; posterior one with pores i10 and i11 connected through single canal, near sphenotic border, ventroposteriorly to eye. Postotic sensory canal extending from posterior limit of optic sensory canal to anterior limit of lateral line, with pore p1 opening on pterotic border. Preopercle-mandibular sensory canal absent. Otic sensory canal short, without pores. Lateral-line canal very short, with three pores. Pore ll1 on postemporal-supracleithrum, pores ll2 and ll3 on lateral side of body posterior to opercle.
Dorsal-fin ii,7, its margin somewhat rounded, with four procurrent rays. Basal dorsal-fin radials eight. Dorsal-fin base located between verticals through 20 th and 25 th vertebra (n = 3). Pectoral fin i,6. Some specimens with minute filamentous extension to tip of first unbranched pectoral-fin ray; others without such extension. Pelvic fin i,4, small with margin rounded, origin located at vertical through about 17-18 th vertebrae. Anal fin ii,5, with three procurrent rays. Anal-fin pterygiophores arranged as six thin, elongate proximal radials

Color in alcohol.
Body color pale brown to light gray, somewhat homogeneous, with minute dark chromatophores distributed throughout; ventralmost lateral portion clearer; ventral surface white. Dorsal surface of head with dark brown area at nape. Nasal barbel dark brown; maxillary barbel pigmented dorsally; rictal barbel light yellow. Dorsal and caudal fins with brown chromatophores along borders of rays; basal portion of dorsal-fin membrane pigmented similarly to body. Pectoral, pelvic and anal fins somewhat lighter, with dark chromatophores restricted to region near base of rays (Fig.  1).
Live coloration. Ground color light yellow to somewhat translucent. Some specimens mottled with pale brown spots. Head pale yellow with scattered grayish-brown chromatophores. Dorsal portion of head with dark central area, posterior to eyes. Ventral surfaces translucent. Fins almost hyaline (Fig. 7).

Distribution.
Known from two tributaries of the rio Itapicurumirim, in the headwaters of the rio Itapicuru basin, northern Bahia State (Fig. 8).
Etymology. The specific name payaya honors the Payayá, an indigenous people who once inhabited the area south of the rio São Francisco, between the upper rio Itapicuru and rio Paraguassu valleys to the Recôncavo Baiano, in northern Bahia State (Dantas et al., 1992). The Payayá occupied the region called "Sertão da Jacobina" until the 18 th Century. Although the Payayá people are considered extinct for a long time, their descendents nowadays inhabit the region of the Chapada Diamantina, in northern Bahia State (Dantas et al., 1992;Santos, 2008).

Discussion
The headwaters of the upper rio Itapicuru, where specimens of Trichomycterus payaya were caught, drain the northern portion of the Chapada Diamantina domain. Neighboring headwaters include those of the rio Paraguaçu to the south and lower stretches of the rio São Francisco to the north and west. A few trichomycterids have been recorded for northeastern Brazil, including four species endemic to headwaters of the rio Paraguaçu: Copionodon pecten, C. orthiocarinatus, Glaphyropoma rodriguesi, G. spinosum, and Ituglanis paraguassuensis (de Pinna, 1992;Campos-Paiva & Costa, 2007;Santos & Caramaschi, 2007;Bichuette et al., 2008) and two species from southern Bahia: Trichomycterus bahianus and T. pradensis (Costa, 1992;Sarmento-Soares et al., 2005). The six Trichomycterus species assigned to the rio São Francisco basin were described from its upper and middle stretches, in Minas Gerais State (Lütken, 1875;Eigenmann, 1918;Costa, 1992;Trajano & de Pinna, 1996;Wosiacki, 2004). The only species reported from the Caatinga of the rio São Francisco valley, at northern Minas Gerais State, is Trichomycterus itacarambiensis (Trajano & de Pinna, 1996;Rosa et al., 2003). Trichomycterus payaya is the first record for the genus in northern Bahia coastal rivers and the only known species inhabiting coastal rivers draining the Caatinga Biome of northeastern Brazil.
A monophyletic assemblage composed of the subfamilies Tridentinae, Stegophilinae, Vandeliinae, Sarcoglanidinae, and Glanapteryginae (called TSVSG clade, sensu Costa & Bockmann, 1993), was defined on the basis of four synapomorphies: posterior elongated process of parasphenoid absent, metapterygoid reduced or absent, interopercular patch of odontodes reduced in length with 15 or fewer odontodes, and six or less epipleurals ribs (Costa & Bockmann, 1993). Scleronema and Ituglanis were recognized as more closely related to the clade TSVSG (de Pinna, 1998), but still remain in the unresolved Trichomycterinae subfamily. Trichomycterus payaya has the lateral process of the urohyal sharp and elongated, a condition very similar to those found in derived trichomycterids such as Trichomycterus hasemani, T. johnsoni, Scleronema, Ituglanis and also the TSVSG clade (as in Costa & Bockmann, 1993;de Pinna, 1998;Wosiacki, 2002). However, the interopercular patch of odontodes is well developed and longer than deep in T. payaya, a condition distinctive from that found in those derived trichomycterids wherein the interopercle is nearly as long as deep and there is a tendency towards bone reduction (de Pinna, 1998). The sharpening of the urohyal lateral process and the reduction of the interopercular patch of odontodes seem to have intermediate states across Scleronema, Ituglanis, and Trichomycterus lineages (Datovo & Bockmann, 2010). The new Trichomycterus species also shares with both Ituglanis and the TSVSG clade a reduced number of epipleural ribs, 5-6 (vs. 9 in Scleronema operculatum). In spite of having those features, T. payaya is not considered a member of the clade composed of Scleronema, Ituglanis, and TSVSG assemblage because it does not have other derived features of this clade, such as interopercular patch of odontodes reduced, as stated above, and three or fewer abdominal vertebrae (de Pinna, 1998).
The non-monophyletic nature of the Trichomycterinae is well known (Baskin, 1973;de Pinna, 1989;de Pinna, 1998) and this subfamily has been gradually eroded by the exclusion of species and groups of species more closely related to other subfamilies (de Pinna, 1998). Although basically diagnosed by the lack of specializations of the other subfamilies, the Trichomycterinae was tentatively diagnosed by Arratia (1990). Trichomycterus payaya possesses the diagnostic characters of the Trichomycterinae (sensu Arratia, 1990), such as basioccipital with well-developed anterior process, enarthrodial articulation between the preopercle and the opercle, vomer with long posterior process, and pronounced notch on posteroventral margin of ceratobranchial 3. Arratia's (1990) proposal for the monophyly of the Trichomycterinae was weakened by de Pinna (1998), on the basis of the absence of the cited characters in Trichomycterus hasemani (Schaefer & Fernandez, 2009). In spite of the controversies regarding the recognition of the Trichomycterinae, the new species is herein considered a member of this subfamily due to overall similarity to Trichomycterus and by virtue of not sharing those characters that diagnose any of the other trichomycterid subfamilies.
The Trichomycterinae is currently composed by Bullockia, Eremophilus, Hatcheria, Ituglanis, Rhizosomichthys, Scleronema, Silvinichthys, and Trichomycterus (Arratia, 1990;Wosiacki & de Pinna, 2008b). Within this subfamily, T. payaya lacks the synapomorphies for Bullockia, Eremophilus, Hatcheria, Rhizosomichthys, and Scleronema (Arratia, 1990) and Silvinichthys (Arratia, 1998;Fernandez & de Pinna, 2005). In comparison to Ituglanis, Trichomycterus payaya lacks the three synapomorphies postulated by Costa & Bockmann (1993) for that genus: (1) supraoccipital fontanel reduced to a small round orifice (vs. wide posterior cranial fontanel between frontals and supraoccipital in T. payaya), (2) palatine with a deep medial concavity and anterior extremity of the sphenotic directed anteriorly (vs. palatine with a medial shallow concavity in T. payaya), and (3) anterior portion of sphenotic directed anteriorly (vs. anterior portion of sphenotic directed laterally, together with posterior border of frontal in T. payaya). We observed that in Ituglanis the infraorbital sensory canal emerges directly from the sphenotic instead of emerging between the frontal and the sphenotic as in T. payaya. In spite of this, T. payaya shares some external morphological features with Ituglanis along the Atlantic coastal rivers (e.g., Ituglanis cahyensis, I. paraguassuensis, I. parahybae, and I. proops), such as a depressed head, low number (usually two) of tooth rows on premaxilla and dentary, shallow abdominal cavity, and dorsal fin posteriorly placed. The proportional distance from the dorsal-fin origin to base of middle caudalfin rays (DFC) in predorsal length (PDL) was employed to check the position of dorsal fin among Trichomycterus and Ituglanis species. We observed a more anterior position of the dorsal fin in Trichomycterus, with the ratio PDL/DFC 1.4-1.9. On the other hand, a more posterior position of the dorsal fin was observed in Ituglanis, with the ratio PDL/DFC 2.2-2.8. In T. payaya the ratio PDL/DFC has intermediate values, 1.9-2.2. Also, the paired supraorbital pore s6 opening laterally on supraorbital sensory branch and not emerging from an epiphyseal branch in T. payaya resembles the condition observed for Ituglanis cahyensis and I. parahybae (illustrated in fig. 2 of Sarmento-Soares et al., 2006). Paired s6 pores separated from each other on the interorbital region, near the cranium border, is also observed in Ituglanis paraguassuensis ( fig. 2c). In Trichomycterus species along Southeastern and Eastern hydrographic regions (T. giganteus, T. nigricans, T. paquequerensis, T. caudofasciatus, and T. pantherinus), the supraorbital pore s6 is placed at the interorbital space, emerging from an epiphyseal branch, even in the specimens with a single symphyseal pore s6. The position of s6 pores in T. payaya is unique among cited Trichomycterus species.