A new species of sexually dimorphic Pareiorhaphis Miranda Ribeiro , 1918 ( Siluriformes : Loricariidae ) from the rio Doce basin , Brazil

Pareiorhaphis nasuta, a new neoplecostomine catfish of the family Loricariidae is described. The species was collected from headwaters of the rio Matipó, tributary of the upper rio Doce basin in State of Minas Gerais, Brazil. The new species is readily diagnosed from all remaining congeners by the longer snout and by the smaller orbital diameter. The new species is the first representative of the genus Pareiorhaphis discovered in the rio Doce basin, thus expanding its geographic distribution. A phylogenetic diagnosis for Pareiorhaphis is presented.


Introduction
Pareiorhaphis Miranda Ribeiro, 1918 is the most diverse genus in the subfamily Neoplecostominae, comprising 17 valid species (Pereira, 2005).These fishes are small to medium-sized suckermouth armored catfishes with maximum standard length between 34 mm (P.nudulus) and 116 mm (P.azygolechis).Pareiorhaphis was recently resurrected from the synonymy of Hemipsilichthys Eigenmann & Eigenmann, 1889 by Pereira (2005), to accommodate several species previously assigned to the latter genus.That resurrection was based on the discovery that three species of Hemipsilichthys plus Delturus belong to a clade that is the sister-group to all remaining loricariids except Lithogenes, and was subsequently described as the subfamily Delturinae by Reis et al. (2006).A new phylogenetic diagnosis of Pareiorhaphis is presented below, based on our ongoing studies, and was used to allocate the new species in Pareiorhaphis.
Nuptial male Pareiorhaphis have similar sexual dimorphism characterized by a thickened pectoral-fin spine and hypertrophied odontodes (integumentary teeth) on the dorsal surface of the pectoral-fin spine and on the lateral margins of the head.Most species of Pareiorhaphis are distributed in the coastal basins of southern, southeastern, and northeastern Brazil, with highest species diversity observed in coastal rivers of Santa Catarina State, from the rio Araranguá basin north to the rio São João.One species, Pareiorhaphis regani was described from the rio Curicuriari, a tributary to the rio Negro in the Amazon basin.Recently, Pareiorhaphis parmula was described from the headwaters of the rio Iguaçu, in the rio Paraná basin, increasing the geographic distribution range of the genus.During the last five years, six new species have been described, which are currently assigned to Pareiorhaphis (Pereira &Reis, 2002 andPereira, 2005).This growth in the rate of species descriptions can be attributed to the increased interest of the taxonomists, but also to the exploration efforts in regions poorly sampled in the past.In recent fish collections made in headwater tributaries of the rio Doce basin, in Minas Gerais State, additional specimens of Pareiorhaphis were collected and discovered to belong to an undescribed species.The present work reports the first record of a Pareiorhaphis species in the rio Doce drainage and again expands the distribution of the genus.

Material and Methods
Institutional abbreviations are as listed in Reis et al. (2003) with the addition of MZUFV Museu de Zoologia João Moojen de Oliveira, Universidade Federal de Viçosa.All morphometric features were measured with digital calipers to the nearest 0.1 mm and were made from point to point under a stereomicroscope.Measurements of bilaterally symmetrical features were made in the left side of the body whenever possible.Body plate counts and nomenclature follow Schaefer (1997).Measurements include: (1) standard length (measured from the snout tip to the last plate in median series, but not including the horizontally elongate plate covering insertion of middle caudal-fin rays); (2) head length (measured from the snout tip to the end of parieto-supraoccipital bone); (3) predorsal length (measured from the snout tip to the dorsalfin origin); (4) postdorsal length (measured from end of dorsalfin base to the last plate in median series, but not including the horizontally elongate plate covering insertion of middle caudal-fin rays); (5) preanal length (measured from snout tip to the anal-fin origin); (6) preadipose length (measured from the snout tip to the adipose-fin spine insertion); (7) dorsal-fin spine length (measured from its origin to its distal tip); (8) anal-fin spine length (measured from its origin to its distal tip); (9) pectoral-fin spine length (measured from its origin to end of osseous spine, disregarding the fleshy tip); (10) ventral-fin spine length (measured from its origin to its distal tip); (11) upper caudal-fin ray (measured from its origin to its distal tip); (12) lower caudal-fin ray (measured from its origin to its distal tip); (13) adipose-fin spine length (measured dorsally from its origin to its distal tip); (14) adipose to caudal fin distance (measured from the adipose-fin origin to last plate in median series, not including the horizontally elongate plate covering insertion of the middle caudal fin rays); (15) trunk length (average of left and right distance from origin of pectoral-fin spine to origin of pelvic-fin spine); (16) abdominal length (measured from a line uniting both pelvic-fin origins to the origin of anal-fin); (17) 31) plates in median series (counted on both sides); (32) plates at dorsalfin base (number of plates in dorsal series along the dorsalfin base); (33) plates between dorsal and adipose fins (number of plates in dorsal series between insertion of last branched dorsal-fin ray and origin of adipose-fin spine); (34) plates between adipose and caudal fins (number of plates in dorsal series from just posterior the adipose-fin membrane to the caudal fin); (35) plates at anal-fin base (number of plates in ventral series along the anal-fin base); (36) plates between anal and caudal fins (number of plates in ventral series between insertion of last branched anal-fin ray and caudal fin); (37) pre-adipose azygous plates (all unpaired plates preceding the insertion of the adipose-fin spine).
Standard length is expressed in millimeters while all other measurements are expresed as percents of standard length, except subunits of the head, which are expressed as percents of head length.In the list of type material museum abbreviation and catalog number come first, followed by the number of specimens in that lot, the number of specimens measured for the morphometric comparisons in parentheses, the range of standard length, locality, date of collection, and collectors.Abbreviations used are SL (standard length) and HL (head length).Comparative material includes the type specimens of all Pareiorhaphis species but P. regani.
Nuptial males of Pareiorhaphis are defined as specimens having the distinctive modifications that involves the shape of the pectoral-fin spine, and hypertrophied odontodes and fleshy lobes on lateral margins of head, although not necessarily being reproductively mature.The remaining specimens included in the list of material examined are a combination of female, male, and immature specimens of both sexes.

Diagnosis
The following characters are also useful to distinguish Pareiorhaphis species from the remaining neoplecostomines.Abdomen naked or with small embedded platelets and lower lip without a series of distinct papillae behind the dentaries (vs abdomen with plates forming a central polygonal path and lower lip with a series of distinct papillae behind the dentaries in Neoplecostomus); infraorbital series of plates forming the lateral edge on the nasal opening and dorsal-fin spinelet usually present (vs infraorbital series of plates not forming the lateral edge of the nasal opening and dorsal-fin spinelet absent in Isbrueckerichthys); adipose fin present (vs absent in Pareiorhina); tooth series in dentary straight or slightly curved and odontodes on ventral surface of pelvicfin spine aligned with the spine axis (vs tooth series in dentary approximately U-shaped and odontodes on ventral surface of pelvic-fin spine turned medially in Kronichthys).

Pareiorhaphis nasuta, new species
Fig. 1 naked.Abdomen almost completely naked, except for one to four small platelets on each side just posterior to gill opening, sometimes absent in specimens smaller than 50 mm SL.Head broad and moderately depressed.Dorsal profile of head broadly round in dorsal view; females and juveniles more slender.Interorbital space slightly concave.Three slightly elevated ridges between orbits and snout tip.Lateral ridges from middle of snout to upper margins of orbits more prominent.These ridges ornamented with short hypertrophied odontodes in nuptial males.Lateral margin of head covered with minute odontodes.Snout gently convex in lateral profile; snout tip with ovoid area of naked skin.Nuptial males with well-developed soft fleshy lobes extending along lateral portion of head.Soft fleshy area ornamented with short hypertrophied odontodes, approximately perpendicular to body axis.Eye small, dorsolaterally placed; orbit diameter 8.6-11.3% of head length.Iris operculum small or absent.Nares ovoid, slightly longer than wide, positioned midway between snout tip and anterior orbit margin.Oral disk circular.Lips roundish and well-developed, occupying most of ventral surface of head.Lower lip almost reaching pectoral girdle, densely covered by minute papillae.Papillae surrounded by naked areas, decreasing in size towards edge.Posterior edge slightly fringed.Maxillary barbel short and united to lip by membrane basally, free distally.Both premaxillae and dentaries angled at approximately 120°, with mesial ends slightly curved inwards.Teeth slender, asymmetrically bifid, medial cusp slightly curved inwards.Lateral cusp minute and pointed, never reaching half length of medial cusp.
Dorsal fin originating on vertical line passing through pelvic-fin origin.Dorsal fin short, not reaching preadipose azygous plates when depressed.Nuchal plate exposed, not covered by skin.Dorsal-fin spinelet present but dorsal-fin locking mechanism non-functional.Dorsal-fin spinelet oval and wider than dorsal-fin spine base.Dorsal-fin spine moderately flexible, followed by seven branched rays.Adipose fin with well-ossified leading spine bearing odontodes.Adipose fin preceded by one or two (rarely three) median unpaired preadipose azygous plate.Pectoral fin moderate in size, with curved and depressed spine, covered by minute odontodes in immature males and females.Nuptial males with pectoral fin spine bearing straight and delicate hypertrophied odontodes on outer and ventral faces.Six branched rays, first and second as long as spine.Subsequent branched rays reduced gradually in size.Posterior margin of pectoral fin straight to slightly round, overlapping pelvic-fin origin when adpressed.Pelvic fin with one spine and five branched rays, not reaching or almost reaching to anal-fin origin when adpressed.Pelvic-fin spine depressed, covered with minute odontodes ventrally and laterally; dermal flap on its dorsal surface present and developed, extending to tip of spine.Pelvic-fin flap distinctly higher near fin base.Anal fin with one unbranched and five branched rays; passing adipose-fin origin when adpressed.Caudal-fin forked; lower lobe slightly longer than upper; 14 branched rays.Upper caudal-fin lobe with five and lower lobe with four ventral plate-like procurrent rays, posteriormost elongate.Odontodes on principal and procurrent rays small and irregurlarly arranged.

Coloration in alcohol.
Ground color of dorsal surface of head and body grayish or sometimes light brown (dark gray in living specimens), whitish or light yellowish ventrally.Dorsum and flanks mostly plain, neither males nor females with small dark spots or saddles on dorsum and flank.Spines and branched rays of dorsal, anal, and caudal fins plain grayish.Caudal fin sometimes with one or two diffuse narrow bands.Paired fins uniformly grayish, occasionally posterior margin of pectoral fin slightly whitish.Spines of pectoral and pelvic fins uniformly grayish dorsally and ventrally.Fin membranes hyaline.Ventral margin of head, outer portion of upper lip, and ventral portion of caudal peduncle dusky.
Distribution.Pareiorhaphis nasuta is known from three localities in Minas Gerais State, the type-locality in the ribeirão Areia Branca, tributary to the rio Matipó, and two sites in the rio Matipó itself.These sites are located in the upper rio Doce basin and are separated by a maximum of 14 km.
Ecology.The ribeirão Areia Branca, type locality of Pareiorhaphis nasuta, is a small (about three to four meters wide), shallow river with very clear, transparent water, and slow to moderate current.The bottom has rocks, loose stones, and sometimes gravel.Grass or other vegetation is present on the margins.Rapids and small pools were found along the stream, but specimens were captured in areas of rapids among loose stones and pebbles.Nuptial males and larger specimens are usually captured among the larger stones and on the stronger current.
Two other populations were sampled on the main channel of the rio Matipó, at Raul Soares (MCP 38808, ANSP 187153, and MZUFV 2567) in 1997 by Jorge Dergam and at Abre Campo (MCP 38809) in 2002 by F. Vieira.The river was 20 to 25 meters wide, one to two meters deep, and with strong rapids.The water was nearly transparent and slightly black, with fast current.The bottom consisted mostly of large stones and boulders.In this area, the new species was syntopic with Astyanax cf.taeniatus, Hypostomus affinis, Harttia sp., Neoplecostomus sp., Trichomycterus spp., Rhamdia quelen, and Geophagus brasiliensis.
Sexual dimorphism.As usual for Pareiorhaphis (e.g.Reis & Pereira, 1999, fig. 2;Pereira & Reis, 2002, fig. 6;Pereira, 2005, fig. 1), nuptial males of Pareiorhaphis nasuta have a slightly thickened pectoral-fin spine with somewhat enlarged odontodes and hypertrophied odontodes on the lateral margins of head.Odontodes also occur in females and juveniles, but are much smaller.Also, nuptial males of most species are distinguished from females by having a dermal flap on the dorsal surface of the pelvic-fin spine, which is absent or very reduced in females.In addition to that, and contrary to most other Pareiorhaphis species, fully developed males of the P. nasuta have a well-developed fleshy flap along the entire length of the posterodorsal margin of the pectoral-fin spine.
Etymology.The specific epithet of Pareiorhaphis nasuta is from the Latin nasutus, meaning long-nosed, in allusion to the long snout, diagnostic of this species.An adjective.

Discussion
The diagnosis of Pareiorhaphis presented above is based on our ongoing phylogenetic studies of the neoplecostomines which encompass most of the neoplecostomine species, including several undescribed, and will be published elsewhere.
Pareiorhaphis is distinguished from Isbrueckerichthys by having the infraorbital series of plates forming the lateral edge on the nasal opening and by having a predorsal spinelet.Pereira (2005) described a new species of Pareiorhaphis, P. parmula, that has one, or rarely two, platelets on each side of the pectoral girdle, just posterior to the gill openings.Pareiorhaphis nasuta shares this feature with P. parmula and have two or three small plates in the same region.Both P. nasuta and P. parmula can be easly distinguished from Isbrueckerichthys by lacking plates on the central region of the abdomen, as seen in Isbrueckerichthys and by having a predorsal spinelet.Furthermore, P. nasuta can be distinguished from P. parmula by the smaller orbital diameter (8.6-11.3vs 12.7-15.9%HL).Finally, the most distinctive feature of P. nasuta is the larger snout length that diagnoses it from all remaining congeners (71.1-75.6 vs 52.8-69.9%HL).
The distribution of Pareiorhaphis is herein extended to include the headwater streams of the rio Doce drainage (Fig. 2), suggesting that the species-level diversity among catfishes of the genus Pareiorhaphis is significantly higher than as previously defined by Pereira & Reis (2002) and Pereira (2005).The occurrence of P. nasuta in the rio Doce basin suggests that the distribution of the genus may be still broader than is presently known.
Hemipsilichthys gobio and H. papillatus and some loricariines.(4) Lateroventral portion of preopercle deeply rugose due to the implantation of hypertrophied odontodes in nuptial males.Present in all Pareiorhaphis species and shared with H. gobio and H. papillatus.The characters shared with the groups above are most parsimoniously interpreted as independently derived according to the discussion of relationships in nuptial males.This character is shared with delturines, Isbrueckerichthys duseni, and some loricariines and hypostomines.(2) Opercle with hypertrophied odontodes in nuptial males.Present in all Pareiorhaphis and shared with Hemipsilichthys and some loricariines.(3) Exposed lateral process of cleithum with hypertrophied odontodes in nuptial males.Present in all Pareiorhaphis species and shared with

Table 1 .
Morphometric and meristic data of Pareiorhaphis nasuta.Values are given as percent of standard length or head length.SD = standard deviation, n = number of specimens, H = holotype.