A new species of Rineloricaria ( Siluriformes : Loricariidae : Loricariinae ) from rio Daraá , rio Negro basin , Amazon , Brazil

Rineloricaria daraha, new species, is described from the rio Daraá, tributary of rio Negro, northwestern Amazonas State, Brazil. The new species is diagnosed by having seven branched pectoral-fin rays, finger-like papillae on the lower lip, a large multi-angular preanal plate, and at least four quadrangular plates of variable size surrounding the preanal plate. The new species is known only from rio Daraá and its waterfalls.


Introduction
Rineloricaria Bleeker, 1862, is the most species-rich genus of the Loricariinae with approximately 60 species (Rodriguez & Reis, 2008;Ghazzi, 2008), and widely distributed from Panama in Central America to northern Argentina, on both slopes of the Andes (Reis & Cardoso, 2001;Covain & Fisch-Muller, 2007).Rineloricaria has been diagnosed by a combination of characters, such as presence of a small postorbital notch, surface of the inferior lip bearing short buttonlike papillae, each hemi-maxilla carrying up to 15 short mandibulary teeth, teeth strong and deeply forked, dark bands on the dorsal region of the body with the first one at the origin of dorsal fin, pectoral fin with one spine and six branched rays, a distinctly polygonal preanal plate usually surrounded by three to five other plates, and conspicuous sexual dimorphism in mature males, consisting of numerous developed odontodes along the sides of the head, on the pectoral-fin spine and predorsal area (Isbrücker & Nijssen, 1992: figs. 34-36).In males, the pectoral-fin spine is often thick, short, and curved when compared to females.Males of some species of Rineloricaria have well-developed odontodes all over the predorsal area.
The genus Hemiloricaria Bleeker, 1862 had been largely considered as a synonym of Rineloricaria until, Isbrücker et al. (2001) resurrected the genus and created two others (Leliella and Fonchiiichthys) to accommodate some species previously included in Rineloricaria, based on differences on sexual dimorphism.Ferraris (2003) maintained Hemiloricaria as a synonym of Rineloricaria, but in 2007, he also resurrected the genus without comments, but did not consider Leliella or Fonchiiichthys as valid.Covain & Fisch-Muller (2007) followed Ferraris (2003) and did not consider Hemiloricaria, Fonchiiichthys and Leliella as valid names.Rodriguez & Reis (2008) partly accepted Isbrücker et al. (2001) phenetic proposition of spliting Rineloricaria and Hemiloricaria.Rodriguez & Reis, however, proposed that Hemiloricaria would comprise a wide distributed group of species (Amazon and non-Amazon species) whereas Rineloricaria would be restricted to species occurring in rio Paraná and its tributaries, and the coastal drainages from Uruguay to northeastern Brazil.
We describe herein a very distinctive new species from rio Daraá, a tributary to the rio Negro, in northwestern of Amazonas State, Brazil, in the genus Rineloricaria, following Covain & Fisch-Muller (2007), but we expect that additional information on the phylogeny and biogeography of this group will eventually clarify the taxonomic limits and phylogenetic relationships of that genus.Boeseman (1976), Reis & Cardoso (2001) and Rodriguez & Miquelarena (2005).Straight-line distances were measured with digital calipers.The term lateral abdominal plate follows Reis & Pereira (2000) terminology for what is sometimes called thoracic plates.Dorsal and pectoral spines refer to the first unbranched and thick ray of each fin.This term is preferred to "unbranched or simple ray" due to the presence of non-pungent spines on some loricariids that are homologous to the unbranched first dorsal and pectoralfin ray in loricariines, and to avoid confusion with the unbranched last rays of all fins.Measurements in Table 1 are expressed as proportions of the Standard Length (SL), except for subunits of the head, which are expressed as proportions of Head Length (HL).Plate counts and nomenclature follow schemes of serial homology proposed by Schaefer (1997).Some paratypes were not measured due to reduced size or bad state of preservation.

Measurements follow
Several Rineloricaria species were not available for close examination and had, therefore, their morphological conditions determined from literature accounts.Institutional ab-breviations are INPA (Instituto Nacional de Pesquisas da Amazônia), MZUSP (Museu de Zoologia da Universidade de São Paulo), NMW (Naturhistorisches Museum Wien), and MCZ (Museum of Comparative Zoology in Harvard).

Rineloricaria daraha, new species
Figs  Diagnosis.Rineloricaria daraha is distinguished from all its congeners by having seven branched pectoral-fin rays (vs.six), long digitiform papillae on the ventral surface of the lower lip (vs.button-like papillae) and by the presence of a large and multi-angular preanal plate limited anteriorly by four or more variably sized plates much smaller than the preanal plate (vs. a quadrangular preanal plate surrounded by three to five polygonal plates slightly smaller than the preanal plate).
Description.Morphometric data in Table 1.Body elongated and depressed.Dorsal profile slightly convex from tip of snout to origin of dorsal fin.Body slender along its whole extension, tapering softly towards base of caudal fin.Ventral profile straight from tip of snout to pelvic fin.Lateral profile from pelvic fin to caudal fin becomes more depressed towards caudal-fin base where body becomes more flattened.Greatest body depth at dorsal-fin base.
Head elongated and depressed.Snout long (53-59% of head length) and pointed with small naked area.Naked area not reaching most anterior pore of infraorbital sensory canal.Orbit small and round, with deep and short lanceolate postorbital notch.Head variably keeled; when present, keel reduced to low ridge in front of eye.
Predorsal area not keeled, except by weak pair of carinae on last predorsal plate.Twenty seven lateral plates conspicuously carinated forming a keel.Two longitudinal and confluent keels meeting at 14 th plate of median series.From this point on, remaining thirteen carinated plates of both lateral series form single keel until base of caudal fin.
Mouth opening small and surrounded by short upper lip and well-developed lower lip.Margin of lip fringed with small filaments.Rictal region with well marked groove.Above groove, line of button-like papillae cover maxillary barbel.Papillae much longer at tip of maxillary barbel.Upper lip with few button-like papillae, lower lip surface covered (densely covered in some specimens) by long digitiform papillae, resembling short filaments.Digitiform papillae concentrated around mouth cavity.Small specimens (smaller than 50 mm SL) with round papillae on lip surface.Buccal papillae present behind dentaries; few buccal papillae on premaxillaries.Most of palate smooth, without papillae, except for straight line with three to five papillae, longitudinally oriented, situated at lateral tip of premaxillaries.Mandibular teeth short but robust, deeply forked: seven to eight teeth on premaxillaries and five to seven on dentaries.Dentary teeth larger than those on premaxilla.
Dorsal fin I,7, anterior and long, running along 8 or 9 dorsal plates; pectoral fin I,7 with spine almost straight on females or non-reproductive males, and thick and curved on mature or almost mature males.Pectoral fin reaching third plate of dorsal lateral series.Pelvic fin i,5 and anal fin i,5, welldeveloped.Pelvic fin reaching little beyond insertion of anal fin mostly in females; pelvic fin of males not reaching anal-fin insertion when adpressed.Pelvic unbranched ray thicker in mature males.Anal fin running along seven plates.Caudal fin i,10,i, bilobed to slightly emarginated, with upper lobe little longer than lower lobe.Dorsalmost caudal-fin ray bearing long and thick filament.
Abdominal surface completely covered by unorganized small quadrangular plates in adults, except for naked gular area.Five or six large lateral abdominal plates.Strong gradient of increasing plate size towards pelvic fin.Abdominal plates tightly packed and forming shield.Anterior borderline of this shield irregular, curved caudad in mid-line in some specimens.Preanal plate present, conspicuously larger than other plates and almost round in shape in some specimens.Preanal plate surrounded by at least four quadrangular plates of largely different sizes, with some much smaller than preanal plate itself.Abdominal plating development following ontogenetic process with young specimens showing abdomen largely naked, with few odontodes spread all over abdominal surface.Young adults (approximately 130 mm) with abdomen completely covered.

Color in alcohol.
Light brown background densely covered with conspicuous black round spots on head; faded and irregularly shaped dark blotches on body.Most spots on head contain pores of cephalic sensory canal.Sphenotic and supraoccipital bordered by soft black connective tissue in recently preserved specimens.Two conspicuous black spots just above naked area behind cleithrum, spots surrounding one or two exits of lateral sensory canal.Five wide dark transverse bands on body: first just behind dorsal-fin base, three bands along caudal peduncle and last one close to caudal-fin base.Bands faded in some specimens.Ventral surface uniform.All fin rays irregularly stained of dark, forming large bands of just spots on fins.Interradial membranes hyaline.Dorsal, pectoral and caudal fins darkened at base.tributary to the rio Negro, in the state of Amazonas, northwestern Brazil (Fig. 4).
Etymology.The specific epithet daraha (Daraá in Portuguese) refers to the type locality.

Discussion
Several species of Rineloricaria have been described from the Amazon basin.Most of these represent a taxonomic challenge due to poor original descriptions and unavailable type material.Rineloricaria phoxocephala (Eigenmann & Eigenmann, 1889), described from Coary, and R. castroi Isbrücker & Nijssen, 1984, are commonly found in big rivers and floating meadows (pers.obs.-LRP).Both species are slender and with few abdominal series of plates.Rineloricaria phoxocephala has a more acute, long snout and dark dots on cephalic and lateral line pores that resemble R. daraha.However, the dots on R. phoxocephala are really reduced and less dense than in R. daraha.Besides, R. phoxocephala has well-organized abdominal plates, rather than the scattered small plates on R. daraha.Rineloricaria castroi has conspicuous markings on the fins, with large alternating bands of dark and light brown (Isbrücker & Nijssen, 1984: fig.1).Rineloricaria lanceolata (Günther, 1868) and R. heteroptera Isbrücker & Nijssen, 1976, are often seen in small sandy-bottom streams (pers.obs.-LRP) and can be identified by color pattern.Rineloricaria lanceolata shows conspicuous coloration consisting of black bands covering dorsal, anal, pectoral and pelvic fins (Isbrücker, 1973: fig. 2).Rineloricaria heteroptera resembles R. daraha on the shape of the head and presence of densely marked dark blotches along the head and body, even reaching the ventral region in some specimens (Isbrücker & Nijssen, 1976;figs. 1, 2).However, R. heteroptera has a longitudinal band along the second and third dorsal-fin rays and large quadrangular abdominal plates organized in series, whereas R. daraha does not have any longitudinal dark bands on fins and the abdomen is covered by very reduced plates without any organization.Rineloricaria beni (Pearson, 1924), R. hasemani Isbrücker & Nijssen, 1979, R. konopickyi (Steindachner, 1879), R. mellini (Schindler, 1959), R. microlepidota (Steindachner, 1907), R. morrowi Fowler, 1940, R. teffeana (Steindachner, 1879) and R. wolfei Fowler, 1940 were reported from the mainstem of the Amazon (Reis et al., 2003) and are very poorly represented or misidentified in fish collections.Rineloricaria eigenmanni (Pellegrin, 1908), R. fallax (Steindachner, 1915), R. formosa Isbrücker & Nijssen, 1979, R. platyura (Müller & Troschel, 1848) and R. stewarti (Eigenmann, 1909) have been reported from the periphery of the Amazon, mainly Guyana Shield and rio Negro basin and represent a group of slender species with three to five organized series of abdominal plates.Rineloricaria formosa, R. fallax, and R. platyura have a color pattern that resembles R. morrowi and R. melini: the presence of a conspicuous dark round spot on the supraocciptal or predorsal area (Isbrücker & Nijssen, 1979: fig. 2, R. formosa).Rineloricaria fallax is easily distinguished from R. daraha by the presence of a large dark spot bordered by two well defined lanceolate dark lines on the predorsal plate (Isbrücker & Nijssen, 1979).
More than 30 species of Rineloricaria were recorded from the Paraná, Uruguay and coastal drainages of northeastern, southeastern and south Brazil.All of those species have the abdominal area completely or partly plated (Rodriguez & Reis, 2008;Ghazzi, 2008).When completely covered, the abdominal plates are organized in series and the preanal plate is surrounded by three large quadrangular plates.Otherwise, the abdomen is almost completely naked, showing only large quadrangular plates between the pelvis and urogenital opening (preanal plate and border plates).Despite the diversity of plating exhibited by these sepcies, none has the pattern described for R. daraha.
Rineloricaria daraha also share some characters with other loricariine genera.R. daraha, for instance, is unique in showing digitiform papillae on the lower lip surface.The elongated papillae on the lower lip and the lack of organization of the abdominal plates in R. daraha resemble the conditions in species of Loricaria.Loricaria, however, differs from all Rineloricaria by the presence of few and hypertrophied mandibulary teeth (R. daraha 7-8 vs. Loricaria spp.3-5), long filaments covering almost the whole surface of both lips (vs.digitiform papillae on the lower lip, more concentrated near the mouth in R. daraha) and lack of a preanal plate (vs. a conspicuous preanal plate in R. daraha).In addition, even young specimens of Loricaria show long filaments on the lips, whereas young specimens of R. dahara have buttonlike papillae.
Among the Loricariinae, only representatives of the genus Lamontichthys and R daraha have seven branched pectoral-fin rays.All remaining Loricariinae have only six branched rays on the pectoral fin (Isbrücker & Nijssen, 1978).
Although the number of pectoral-fin rays and the lip structure found in the new species are unique within Rineloricaria, sexual dimorphic features of the mature males are similar to those found in several species of Rineloricaria (R. castroi, R. phoxocephala, R. heteroptera, and others), and unlike those found in species of Loricaria.