Ituglanis agreste , a new catfish from the rio de Contas basin , northeastern Brazil ( Siluriformes : Trichomycteridae )

Ituglanis agreste, a new species of catfish, is described from a tributary stream of the rio Gongogi drainage, rio de Contas basin, Bahia State, northeastern Brazil, from a transition area between the Atlantic Rain Forest and the semi-arid Caatinga savanna. This species is distinguished from its congeners by the following characters: elongate interopercle plate with high number of odontodes (26-30), high number of ribs (5-6), fewer vertebrae (36), number of branchiostegal rays (7), number of pectoral-fin rays (i,6) and absence of s1 pore. Comparisons with other Ituglanis species and putative plesiomorphic characters are presented. Some comments about conservation of Ituglanis species from northeastern Brazil are also made.


Introduction
The genus Ituglanis Costa & Bockmann is a monophyletic assemblage of small trichomicterid catfishes, previously included in Trichomycterus Valenciennes (Trichomycterinae) due to its superficial similarity with the members of this genus.Thus, a new taxon was proposed to accommodate species that share three synapomorphies present in the neurocranium: sphenotic directed anteriorly, parieto-supraoccipital fontanel reduced to a small orifice or completely closed (e.g., in I. macunaima Datovo & Landim, and some specimens of I. epikarsticus Bichuette & Trajano and I. mambai Bichuette & Trajano;Bichuette & Trajano, 2008), and autopalatine with a deep concavity in the inner medial portion (Costa & Bockmann, 1993).The Ituglanis assemblage has been considered essential for understanding the emergence of the morphological and ecological adaptations in the trichomycterids (de Pinna, 1998).This is due to the intermediary phylogenetic position between both the more generalized forms (Trichogeninae, Copionodontinae, and Trichomycterinae) as well as the specialized forms that comprise the TSVSG clade (Tridentinae, Stegophilinae, Vandelliinae, Sarcoglanidinae, and Glanapteryginae), which all share a smaller number of ribs (2-7) (e.g., I. passensis Fernandez & Bichuette).
The coastal watersheds of eastern Brazil north of the rio Pardo have their upper reaches within the temporary rivers of the Caatinga biome, while the lower reaches are in the Atlantic Forest biome.In contrast, watersheds south of the rio Jequitinhonha are entirely in the Atlantic Forest biome (Langeani et al., 2009).While Ituglanis paraguassuensis was only recorded in the semi-arid Caatinga, I. cahyensis is restricted to the pluvial Atlantic forest.This paper describes Ituglanis agreste, a new species of catfish from the rio de Contas basin, found in a transition area between the Atlantic Forest and the Caatinga savanna.
Description.Morphometric data for holotype and paratypes are given in Table 1.Body elongated, subcylindrical about to dorsal-fin origin, and gradually compressed in caudal peduncle.Dorsal and ventral side view straights, except in dorsal part of the head, which is slightly convex.Head depressed, longer than wide, rounded in dorsal view.Eyes rounded and small, without free orbital margin, covered by a thin translucid membrane, lightly located on anterior half of head.Barbels and head covered by minute papillae.Mouth subterminal.Tip of nasal barbel reaching posterior edge of opercular patch of odontodes; tip of maxillary barbel reaching pectoral-fin base and tip of rictal barbel reaching posterior edge of interopercular patch of odontodes or the anterior edge of pectoral-fin.
Mesethmoid with the anterior portion and shaft nearly straight, gradually tapering at proximal tip (Fig. 2a).Lateral ethmoid without lateral projections.Anterior fontanel restricted to small pit with small enlargement in posterior third of frontals.Posterior fontanel as small round opening on posterior portion of parieto-supraoccipital.Sesamoid supraorbital elongate, slender and curved, without lateral process, slightly longer than autopalatine; sphenoticprootic-pterosphenoid narrow, with anterior portion anteriorly directed (Fig. 2a).Pterotic with posterolateral projection.
Autopalatine with a deep concavity on the internal medial border; posterior process moderate, about 50% of the length of the autopalatine (Fig. 2a).Posttemporosupracleithrum with anterior and posterior processes.Vomer arrow-shaped, with thin lateral projections and long posterior process (Fig. 2b).Parasphenoid with two anterior and one posterior processes.Weberian capsule fused to basioccipital and exoccipital and with small lateral opening on each side.Premaxilla trapezoidal and curved with two rows of conical teeth.Maxilla curved with developed ventral process, smaller than premaxilla (Fig. 2a).Dentary almost straight with two regular rows of conical teeth and with pronounced coronoid process (Fig. 3).
Hyomandibula with an anterior laminar projection, a deep depression in dorsolateral portion and pores on anterior and dorsomedian regions (Fig. 4).Anterior portion of quadrate laminar and pronounced.Metapterygoid large, laminar and somewhat trapezoidal, articulating to quadrate by a cartilaginous block and to hyomandibula by bone contact area.Interopercular plate broad and elongate bearing conspicuous posterior projection, with 26-30 odontodes placed in two rows, including in anteroventral projection (Fig. 4).Opercle with 16-17 odontodes.Odontodes conical, curved on the opercular patch of odontodes and thinner on interopercular patch of odontodes.Parurohyal with conspicuous central foramen and lateral process laminar and elongated, gradually tapering from base to tip, with about same length of ceratohyal (Fig. 5).Ventral hypohyal with deep depressions for articulation with parurohyal condyles.Seven branchiostegal rays.
First basibranchial absent, second and third basibranchials ossified with anterior and posterior cartilaginous tips; and fourth basibranchial consisting of elongated, flattened and rounded cartilage (Fig. 6).First hypobranchial 1 ossified and stem-like; second elongate somewhat trapezoidal, mostly cartilaginous except for anterolateral process; third flattened cartilaginous with ossified anterolateral process.First, second, third, and fourth ceratobranchials ossified with cartilaginous tips, and with posterolateral laminar expansions; fifth one curved with small teeth on anterior half.First epibranchial with long anterior process; second with two small alternated process; third with one rounded posterior process; fourth flattened, somewhat rectangular; fifth absent or not evident.First and second pharyngobranchials absent; third and fourth stem-like, this last attached to tooth plate.Upper pharyngeal tooth plate with conical teeth arranged in two rows in ventromedial region (Fig. 6).
Coloration.Body with diffuse and irregular blotches on yellow background.Chromatophores more concentrated in dorsal and lateral region of body, forming large and irregular blotches.In lateral region, chromatophores less concentrated and blotches more dispersed.Ventral region spotless from isthmus to pelvic-fin base, region posterior to pelvic fin with diffuse, irregular and scattered blotches.Caudal penducle with smaller irregular blotches, but more  defined.Chromatophores more concentrated in dorsolateral region of head and opercular patch of odontodes.Nasal, maxillary, and rictal barbels with chromatophores irregularly distributed throughout its entire length.Ventral region of head with chromatophores forming conspicuous spot on lower lip and with irregular and scattered blotches in anterior region to isthmus and interopercle (Fig. 1c).Fins with few chromatophores, more often at base of these.Some individuals exhibit lighter color than others, but following same color pattern.
Distribution.Ituglanis agreste is only known from the type locality, in rio Tarugo, municipality of Boa Nova, Bahia, northeastern Brazil.This river is a tributary of the rio Uruba, that flows into rio Gongogi, principal drainage of right margin on the middle section of rio de Contas basin (Fig. 10).This is the transition zone of the Serra da Ouricana, where small remnants of a formerly extensive humid forest that delineates the limits of the Atlantic Forest domain in the region (Gonzaga et al., 1995).Just a few kilometers to the west, the landscape gives way to the semi-arid Caatinga region, typically known for regular droughts.Thus, it is possible that the rio Tarugo represents the western geographical limit of distribution for this species.During a two year sampling (2008 -2009) along a 325 km transect of the rio de Contas (between the municipalities of Ibuaçussê and Uruçuca), Ituglanis agreste was found only at one site.
Etymology.The specific name "agreste" (from latim agrestis, which means relative to land, field, wild, or rustic) refers to a semi-humid narrow strip parallel to the coast in northeastern Brazil, encompassing the area between the Rio Grande do Norte State to the middle section of rio de Contas basin in Bahia State (Forattini et al., 1981), that marks the transition between two distinct biomes, the Atlantic Forest and the semi-arid Caatinga (Prado, 2003), where the new species was discovered.A noun in apposition.
Ecological notes.Ituglanis agreste was found along a stretch of about 200 m in a mid-small size river with width up to 8 m, in a moderate slope with clear and cold water, with transparency of about 2 m (Fig. 7).The water flow was mainly turbulent, with alternating areas of currents and pools, though a predominance of moderate to strong  drifts.Substrate consists of rocks or sand.The most common depth observed was about 0.5 m, but some parts had about 1.7 m.Some sites had underwater aquatic macrophytes and riparian vegetation.The backwaters area had vegetation composed of Typha sp.The margins were deforested and the environment was mainly composed of pastures.A reservoir without a lake formed by the dam of the river was observed above the collection site.Other species collected with Ituglanis agreste were: Astyanax bimaculatus (Linnaeus), Callichthys callichthys (Linnaeus), Geophagus brasiliensis (Quoy & Gaimard), Rhamdia quelen (Quoy & Gaimard) and Poecilia reticulata Peters, this last an exotic species.
Ituglanis valid species usually show interopercle plate reduction and less odontodes (10-17), a derived character shared with the most specialized forms of the family, assembled in the large clade TSVSG (de Pinna, 1998).At least I. proops presents an elongate interopercle plate (de Pinna & Keith, 2003;Datovo & Bockmann, 2010), a character also observed in I. agreste.Ituglanis agreste also presents some others putative plesiomorphic characters, observed in most species of Trichomycterus and Trichogenes Britski & Ortega: the few number of vertebrae (36) and anal-fin origin inserted on a vertical at 23 rd vertebra.Both features are also present in I. paraguassuensis (Campos-Paiva & Costa, 2007), which suggests a basal position to these species within the genus.Nevertheless, no formal phylogenetic analysis among Ituglanis species has been made yet, and the relationships among them remain unknown (Datovo & Landim, 2005;Wosiacki et al., 2012).If corroborated, these results indicate that the genus Ituglanis could be another example of the "biogeographic pattern B" proposed by Ribeiro (2006) for several freshwater fish groups in the coastal drainages of eastern Brazil, including another trichomycterid genus, the Sarcoglanidinae Microcambeva Costa & Bockmann.Such pattern makes sister-group relationships found in the coastal basins of Brazil and subsequent irradiation with the most inclusive groups located inside the Brazilian Shield and the rio Amazonas basin (Ribeiro, 2006).
Although situated between two coastal basins of Bahia with Ituglanis species previously described: I. paraguassuensis, from the rio Paraguaçu basin adjacent in the north; and I. cahyensis from rio Cahy basin in the south, the diagnostic features of the new species of rio de Contas basin gives enough evidence to differentiate from these two species formally described, confirming the restricted distribution of most species of the genus.
The most conspicuous differences between I. agreste and I. paraguassuensis are found in interopercle patch of odontodes (elongate with 26-30 odontodes vs. reduced with 14-15 odontodes), and should not be related to ontogenetic development once individuals of similar range size were observed (3 c&s, 32.8-41.9mm SL vs. 3 c&s, 30.3-39.6 mm SL).According to Arratia et al. (1990) these integumentary teeth arise very early during ontogeny (Datovo & Bockmann, 2010), indicating that Ituglanis from rio de Contas and rio Paraguaçu are not conspecific.They can be also distinguished by the number of branchiostegal rays, (7 vs. 8) and lack of s1 pore (vs.presence).Nevertheless, they share some diagnostic features used to distinguish other Ituglanis, as 36 vertebrae, seven pectoral-fin rays (i,6) and six pair of ribs.The number of vertebrae shared by them, was referred as an unusual condition among the genus (Campos-Paiva & Costa, 2007), but it is shared at least by other five species (I.nebulosus, I. passensis, I. ramiroi, I. epikarstikus and I. bambui; Fernández & Bichuette, 2002;de Pinna & Keith, 2003;Bichuette & Trajano, 2004).The troglomorphic species from Central Brazil and a few specimens of I. ina also presents a high number of interopercle odontodes (more than 24, except in I. epikarsticus) but differ in some aspects from I. agreste (pectoral-fin rays i,7 or i,8 and some degree of reduction of eyes and pigmentation in subterranean species or usually i,5 and homogeneous color pattern with dark vertical bar in caudal peduncle in I. ina vs. i,6 and spotted color pattern; Bichuette & Trajano, 2008;Wosiacki et al., 2012).
Although the color pattern of I. agreste is similar to I. paraguassuensis, both with a yellow background body covered by blotches, in I. agreste the spots are more diffuse and irregular than I. paraguassuensis, that presents blotches more conspicuous (Campos-Paiva & Costa, 2007).The concentration of chromatophores is more intense in I. agreste, covering the dorsal and lateral region of the body, which gives a darker appearance to I. agreste, if compared to I. paraguassuensis, in which the pigmentation is slightly more concentrated near the eyes and opercular region.
The type locality of Ituglanis agreste is located in the coastal strand of the Serra da Ouricana, which holds important small remnants of a formerly humid forest (Gonzaga et al., 1995) and delineates the westernmost limits of the Atlantic Forest domain bordering with the Caatinga biome.In northeastern Brazil these transition zone are referred as "agreste", which corresponds to a semi-humid climate (Fig. 10).
The three species of Ituglanis described to the northeastern Brazil were found in streams placed in distinct climate and vegetation domains: I. paraguassuensis in the Caatinga, I. cahyensis in the Atlantic Forest and I. agreste was collected in a transition area between these two biomes.Unlike rio Cahy basin, which is a small coastal basin fully inserted in the Atlantic forest domains, the rio Paraguaçu and Contas basins are perennial middle size rivers, with some intermittent tributaries in the upper and middle stretches in the Caatinga region, and lower stretches in the Atlantic Forest (Rosa et al., 2003).
The collection site was highly degraded due to anthropogenic impacts, mainly removal of riparian vegetation for agriculture and cattle (Fig. 11) in Boa Nova adjacencies.According to Gonzaga et al. (1995) the forest environments in Serra da Ouricana are among the most neglected habitats for conservation.Only recently this region was recognized of a high importance for conservation (MMA, 2007), which led to the creation of new conservation units in 2010: Boa Nova National Park (PARNA) and Boa Nova Wildlife Refuge (REVIS), with the aim to preserve the natural ecosystems of the transition area between Atlantic forest and Caatinga, protect endangered species and maintain water sources/springs and streams (Brasil, 2010).Cetra et al. (2010), in a study of freshwater fish promoting the expansion and implementation of conservation units in southern Bahia, conduct ichthyological surveys in the rio Cachoeira, Colônia, Contas, and Jequié basins, including these new protected areas in Boa Nova, near the type locality (about 9 km east).These authors only recorded the presence of Ituglanis sp. about 120 km south of the type locality of I. agreste, in the rio Cachoeira basin.Because the taxonomic status of Ituglanis sp.collected in the rio Cachoeira basin remains uncertain, it could belong to a previously described species or a distinct new species.Regardless, I. agreste most likely occurs in the new conservation areas in Boa Nova (PARNA and/or REVIS), since these protected areas are situated near the type locality where the new species was collected.
The protection of water courses and their riparian margins through the creation of conservation units is among the most important measures concerning the future and diversity of fish species of the coastal basins of Brazil (Menezes et al., 2007).Fortunately, the three species of Ituglanis known from Bahia (including the one described herein), are found in hydrographic basins that pass through integral protection conservation units: I. paraguassuensis in the rio Paraguaçu basin that passes through the Chapada Diamantina National Park, I. cahyensis in the rio Cahy basin that has part of it course protected by the The discovery of this new species in the rio de Contas basin reinforces the necessity for ichthyofaunal inventories in northeastern Brazil, especially in the numerous isolated coastal watersheds south of rio São Francisco, where more undescribed species are expected to exist (Langeani et al., 2009).In the last three years, six new fish species were described for the rio de Contas basin: Cyphocharax pinnilepis Vari, Zanata & Camelier, Gymnotus interruptus Rangel-Pereira, Hasemania piatan Zanata & Serra, Hyphessobrycon brumado Zanata & Camelier, a distinct species from H. negodagua that inhabits the rio Paraguaçu basin, Leporinus brinco Birindelli, Britski & Garavello, Trichomycterus tete Barbosa & Costa (Vari et al., 2010;Zanata & Camelier, 2010;Zanata & Serra, 2010;Barbosa & Costa, 2011;Rangel-Pereira, 2012;Birindelli et al., 2013).Hence, the case of Ituglanis agreste, together with the recently discovered endemic fish above, suggests that the rio de Contas basin contains several endemic species (Zanata & Camelier, 2010).

Fig. 10 .
Fig. 10.Geographic distribution of the three Ituglanis species in northeastern Brazil.The locality of Ituglanis agreste (rio Tarugo) represents the type locality.