A new species of Hemiancistrus from the rio Araguaia basin , Goiás state , Brazil ( Siluriformes : Loricariidae )

Hemiancistrus cerrado is described from the tributaries of rio Araguaia, rio Tocantins basin. Hemiancistrus cerrado has external similarities with H. megalopteryx and H. punctulatus from coastal streams of southern Brazil, and can be distinguished by having a larger internarial width, 15.9-21.1% of head length (vs. 11.2-14.0% in H. megalopteryx and 11.2-13.9% in H. punctulatus) and, with little overlap, by the larger adipose-fin spine length, 9.4-13.6% of standard length (vs. 7.1-8.7% in H. megalopteryx and 7.4-10.0% in H. punctulatus). Hemiancistrus cerrado further differs from H. megalopteryx by having the pectoral-fin spine reaching maximally to the middle of the pelvic-fin spine when adpressed in adult males (vs. reaching tip). Hemiancistrus cerrado differs from other members of Hemiancistrus by color and numerous morphometric and meristic data.


Introduction
The Cerrado region of central Brazil, is a biologically rich savanna and currently one of the most threatened biomes of South America (Oliveira & Marquis, 2002).With the increasing expansion of agricultural activities, there has been a rapid reduction of the biodiversity in this unique ecosystem (Klink & Moreira, 2002).The 1.2 million km 2 area contain tributaries of three of the major river basins in South America: the Amazon, Paraná-Paraguay and São Francisco rivers.In 2005 an expedition was taken to the Cerrado region of Brazil to explore the freshwater fish diversity, as part of the All Catfish Species Inventory Project.The focus was in the tributaries of the rio Araguaia in Goiás State.A new species of loricariid catfish was discovered and is being described in this issue, Hemiancistrus cerrado.
The genus Hemiancistrus Kner includes 15 valid species and is found in most tropical cis-Andean regions of South America and in Pacific coast drainages in Ecuador.Armbruster (2008) completed a phylogeny with representatives of all species groups of Hemiancistrus and found the genus to be paraphyletic; and he moved Peckoltia sabaji to Hemiancistrus.Armbruster (2008) defines Hemiancistrus phenetically as those species in his Panaque clade lacking the synapomorphies of the other genera and by having the dentaries meet at an angle greater than 120° (vs.<90° in Peckoltia).In addition to the 15 species currently recognized in Hemiancistrus, Armbruster (2004Armbruster ( , 2008) ) H. sabaji, H. snethlageae, H. spilomma and H. spinosissimus. Hemiancistrus micromattos, H. spilomma, and H. spinosissimus are also found in the Tocantins basin.Hemiancistrus cerrado is described herein from the rio Vermelho and rio Crixás-Açu, tributaries of rio Araguaia in the rio Tocantins basin.

Materials and Methods
Counts and measurements follow Armbruster (2003).Institutional abbreviations are as listed at http://www.asih.org/codons.pdf.Specimens were cleared and stained for examination of bone and cartilage following the methods of Taylor & Van Dyke (1985).Names of plate rows follow Schaefer (1997).The following are abbreviations used in the text: CS = cleared and stained, D = distance, Dia = diameter, Dp = depth, dr = drainage, HL = Head length, L = length, W = width.All specimens were measured and examined for meristics.

Hemiancistrus cerrado, new species
Figs Eyes moderately sized, dorsal rim of orbit forming tall crest that continues forward to area just anterior of nares as low, rounded ridge.Interorbital space largely flat, but with slight, rounded, median hump contiguous with rounded ridge on snout formed from mesethmoid.Slight ridge formed between anterodorsal margin of orbit and nares.Supraoccipital pointed posteriorly with posterior point raised above nuchal region in small crest.Infraorbitals, frontal, nasal, pterotic, and supraoccipital supporting odontodes.Preopercle and opercle not supporting odontodes.Opercle sickle shaped.
Lips covered with short, wide papillae.Size of papillae decreasing towards posterior margin of lower lip, bucal central papillae present and well developed.Lower lip wide, upper lip narrow.Edge of lower lip with small crenulae.Maxillary barbel reaching about one-third of distance to gill opening.
Median plates 24-27 (mode 25).Plates unkeeled, but first four or five plates of mid-ventral series bent to form slight ridge.Five caudal peduncle plate rows.Plates on all dorsolateral surfaces of body except for extreme edge of snout that only has narrow column of platelets on either side of snout tip.Throat mostly covered in platelets except for area right below lower lip.Abdomen naked or sparsely covered in platelets over and slightly posterior to pectoral bridge, laterally between pectoral and pelvic fins, and small region around anus.Cheek plates supporting hypertrophied odontodes evertible perpendicular to head.Cheek odontodes nine to 29 (mode 15).Longest evertible cheek odontode reaching middle of lateral process of cleithrum.Hypertrophied cheek odontodes relatively weak.Slightly longer odontodes present along dorsal-, adipose-, pelvic-, caudal-, and pectoralfin spines; larger individuals with hypertrophied odontodes at tip of pectoral spine.Dorsal fin II,7; dorsal-fin spinelet V-shaped, dorsal-fin locking mechanism present, last ray of dorsal fin almost reaching adipose-fin base when adpressed.Adipose fin with single preadipose plate and moderately long spine.Caudal fin I,14,I; caudal fin slightly emarginate, ventral lobe longer than dorsal lobe; dorsal and ventral procurrent caudal rays four to five (mode four).Pectoral fin I,6; pectoral-fin spine Color.Base color brown or gray in preserved specimens.Head and nape almost completely dark brown with large dark spots sometimes becoming mottled distally.Pectoral fin brown with dark brown large oblong spots on fin membranes and rays.Pectoral, pelvic, dorsal, anal and caudal fins slightly lighter than body, with dark, large oblong spots on fin membranes and rays.Spots in caudal fin arranged in three to five regular (contiguous along height of fin) or irregular (ventral and dorsal parts offset) bands; lighter interspaces light gray, usually slightly narrower than spots.Largest individual examined with light interspaces much narrower than spots, spots very irregular.Body with four saddles slightly darker than intervening areas, first below anterior end of dorsal fin, second with anterior half below posterior end of dorsal fin and posterior half behind dorsal fin, third beginning one to two plates anterior of preadipose plate to about posterior third of adipose-fin membrane, and fourth beginning just posterior to adipose fin to end of caudal peduncle.Ventral surface uniformly light except for blotches from anterior insertion of anal fin to caudal fin.Color in life similar to preserved coloration except base light brown and spots on body more intense.Distribution and habitat.Known from rio do Bugre, rio Vermelho and probably rio do Peixe, tributaries of rio Araguaia in Goiás State, Tocantins Basin (Fig. 3).Collected in second order streams in swift rocky riffles (Fig. 4).
Etymology.Named after the Brazilian Cerrado, where the species is found.A noun in apposition.

Discussion
Hemiancistrus cerrado, H. micromattos, H. spilomma, and H. spinosissimus are species known from the rio Araguaia-Tocantins basin.Hemiancistrus cerrado is distinguishable from H. micromattos, H. spilomma and H. spinosissimus by having an emarginate caudal fin (vs.forked).In addition, the dentaries of H. cerrado form almost a straight line, whereas the dentaries in H. micromattos, H. spilomma, and H. spinosissimus form a distinct angle approaching 90° in some specimens.Morphologically Hemiancistrus cerrado is most similar to H. punctulatus, which is found in laguna dos Patos drainage in Southern Brazil.Considering the great distance between the drainages systems of Southern Brazil and the Cerrado region, it is extremely unlikely that these two populations are conspecific; however, only one difference (internareal width) was found to distinguish them.
All specimens of Hemiancistrus cerrado were found in the Araguaia drainage in close proximity of each other.Their range is in the central region of the Cerrado, which is being heavily impacted by the rapid destruction of the Cerrado biome (Cavalcanti & Joly, 2002).Threats to the Araguaia drainage include agricultural erosion, pesticide runoff and mercury in the tributaries from gold mining.The uniqueness of the region as well as the fauna of the Araguaia is in urgent need of protection.Oliveira & Marquis (2002) recognized this region to be a priority for conservation and urged for a proactive conservation approach.Table 1.Selected morphometrics of Hemiancistrus cerrado.Numbers in parentheses refer to landmark numbers in Armbruster (2003).Measurements are ratios of SL (predorsal length to pelvic-dorsal length) or head length (head-eye length to premaxillary tooth cup length).
removes several species to what he calls the Hemiancistrus annectens group; these species of trans-Andean fishes are unrelated to true Hemiancistrus and may represent an undescribed genus of the Pterygoplichthyini.Reviews of Hemiancistrus sensu stricto and the H. annectens group are under way by JWA, and morphometric data is based on that study.Five other species are known from the Amazon basin, H. micromattos, and eye); and from H. sabaji by having the spots on the sides all about the same size (vs.gettinglargerposteriorly) and the spots separate on the caudal fin (vs.combining to form bands on the lower lobe in adults).Hemiancistrus cerrado is very similar to H. megalopteryx and H. punctulatus but can be distinguished by having a larger internares W/HL (15.9-21.1% vs. 11.2-14.0% in H. megalopteryx and 11.2-13.9% in H. punctulatus), can usually be distinguished by having a larger adipose-fin spine L/SL ratio (9.4-13.6% vs. 7.1-8.7% in H. megalopteryx and 7.4-10.0%inH.punctulatus); and from H. megalopteryx by having the pelvic-fin spine reaching maximally to the middle of the pelvic fin spine when adpressed in adult males (vs.reaching the tip).Morphometrics in Table1.Largest specimen examined 170.3 mm SL.Counts and measurements based on 13 specimens.Head and nape forming arc from tip of snout to insertion of dorsal fin.Dorsal slope decreasing in straight line to insertion of dorsal procurrent caudal rays then ascending to caudal fin.Ventral profile flat to caudal fin.Caudal peduncle triangular in cross section with dorsal surface flattened.Body widest at insertion of pectoral fins, narrowest insertion of caudal fin.Snout rounded.