Two new species of Moenkhausia Eigenmann (Characiformes: Characidae) from Serra do Cachimbo, Pará, Northern Brazil

Two new species of Moenkhausia, one from the rio Tapajós and the other from the rio Xingu basins are described as apparently endemics of the Serra do Cachimbo. Both species, along with M. petymbuaba, share a distinct color pattern composed of large conspicuous dark blotches on the base of the body scales. Moenkhausia chlorophthalma, from rio Treze de Maio, a tributary to rio Curuá (rio Xingu basin), is distinguished by the presence of a proximal well delimited black area on the adipose fin and a green eye in life. Moenkhausia plumbea of the headwaters of tributaries of the rio Braço Norte, rio Tapajós basin is diagnosed by the presence of a dark longitudinal stripe across the eye and six branched pelvic-fin rays (vs. seven). Relationships of the new species with other Moenkhausia are discussed.


Introduction
In the first attempt to group the species of Moenkhausia into subunits, Géry (1977) recognized three assemblages within the genus based on Eigenmann's (1917: 66-69) key to the species of Moenkhausia: the M. lepidura-group (shallow-bodied species with relatively few horizontal scale rows on the body); the M. grandisquamis-group (deepbodied species with relatively few horizontal scale rows); and the M. chrysargyrea-group (deep-bodied species with relatively numerous horizontal scale rows).Géry (1992) later focused his analysis to the M. lepidura-group especially to those species having a distinct dark mark on the upper lobe of caudal fin, independent of body depth or number of horizontal scale rows.Lucinda et al. (2007) recently described M. hysterosticta as a possibly member of that group.Costa (1994) did not follow Géry's (1977) grouping, suggesting instead a new assemblage comprising M. oligolepis, M. pyrophthalma, and M. sanctaefilomenae.This group was defined by the presence of a distinct reticulate color pattern and a "black bar over the terminal portion of caudal peduncle and basal portion of caudal fin that is preceded by a light area on the caudal peduncle".Lima & Toledo-Piza (2001) described M. dyktiota as possibly related to this assemblage, and more recently two species were added to Costa's (1994) group: M. cosmops (Lima et al., 2007), and M. forestii (Benine et al., 2009).Lima & Birindelli (2006) described Moenkhausia petymbuaba, based on specimens collected in Serra do Cachimbo, which is the main geographical barrier between the middle courses of the rio Xingu and the rio Tapajós, where the headwaters of those drainages lie close to each other and are in some cases only separated by a few meters.Goulding et al. (2003) suggested a high level of endemism for the species from the Serra do Cachimbo, suggestion confirmed by subsequent collections (Birindelli et al., 2009a;Sabaj Pérez, 2009).The description of Jupiaba kurua (Birindelli et al., 2009b), and Leporinus guttatus (Birindelli & Britski, 2009) from the rio Curuá provided evidence that the fish fauna upstream of the falls at Cachoeira da Serra was isolated from the rest of the drainage and is apparently highly endemic.
Two undescribed species of Moenkhausia, one from the rio Tapajós and another from the rio Xingu basins were discovered in small creeks located near the headwaters of the rio Curuá, with these portions isolated by large waterfalls from downstream portions of those systems.We herein describe both new species, discuss their possible relationships with congeners, and contribute to the understanding of the endemism in the Serra do Cachimbo.

Material and Methods
Counts and measurements follow Fink & Weitzman (1974), Menezes & Weitzman (1990) and Lima & Birindelli (2006).All measurements were made point-to-point on the left side of the specimens whenever possible with dial calipers and data recorded to tenths of a millimeter.Standard length is presented in mm, all other measurements are presented as proportions of standard length, except subunits of head wich are presented as proportions of head length.Meristic data are given in the description and are followed by the frequency for each count in parenthesis with an asterisk indicating counts of the holotype.Vertebrae, supraneurals, procurrent caudal-fin rays, branchiostegal rays, gill-rakers, teeth counts and numbers of teeth cusps were taken from cleared and stained paratypes (c&s) prepared according to Taylor & van Dyke (1985).Vertebrae of the Weberian apparatus were included in the precaudal counts as four elements, and the fused PU1+U1 was counted as a single element.Pattern of circuli and radii was defined on scales taken from the region between the lateral line and the dorsal-fin origin.Institutional abbreviations follow Ferraris (2007).
Dentary and premaxillary bones for Scanning Electron Micrographs (SEM) images were prepared by the following procedure: they were removed from cleared and double stained specimens, immersed in weak (less than 1%) sodium hypochlorite solution and dried using successively more concentrated solutions of alcohol and, subsequently, acetone.

Moenkhausia chlorophthalma, new species
Figs. 1-3 Diagnosis.Moenkhausia chlorophthalma is distinguished from all congeners, except M. petymbuaba and M. plumbea by the presence of large dark blotches on the anterior to central portions of the scales forming the seven dorsalmost longitudinal series (vs.pigmentation absent or, when present, concentrated posteriorly along the border of the scales, and forming a reticulate pattern on the body).Moenkhausia chlorophthalma can be differentiated from both M. petymbuaba and M. plumbea by the possession of a proximal well-delimited black area on the adipose fin (vs.adipose fin with uniformly scattered dark chromatophores), 7 longitudinal rows of large dark blotches (vs.8-9), 25-28 lateral line scales (vs.33-36), 4 scales between the lateral line and the dorsal-fin origin (vs.5), and 7-12 scales covering the anal-fin base (vs.[4][5][6][7][8][9].Moenkhausia chlorophthalma can be further separated from M. petymbuaba by lacking a conspicuous midlateral dark stripe (vs.presence of  Description.Morphometric data presented in Table 1.Overall size small (largest examined specimen 67.4 mm SL).Body compressed, moderately elongate.Greatest body depth located slightly anterior to dorsal-fin origin.Dorsal profile of head slightly convex from upper lip to vertical through nares; mostly straight from latter point to tip of supraoccipital spine; convex from tip of supraoccipital spine to dorsal-fin origin, straight from near of dorsal fin base to adipose fin; slightly concave between latter and origin of anteriormost dorsal procurrent caudal-fin ray.Ventral profile of head and body distinctly convex from lower lip to anal-fin origin; straight along anal-fin base, and concave between terminus of analfin and anteriormost procurrent caudal-fin ray.Mouth terminal.Posterior limit of maxilla almost reaching vertical through middle of orbit.Premaxillary teeth in two rows (Fig. 3).Outer row with four (1) or six (1), relatively compressed, tricuspid teeth.Inner row with five (2) bulky tri-to pentacuspid teeth.Symphyseal tooth largest, asymmetrical, with single lateral cusp on anteromedial margin.Maxilla with three equal-sized tricuspid teeth.Dentary with four anteriormost teeth large, robust, pentacuspid, followed by a series of distinctly smaller, conic or tricuspid teeth.First gill arch with 1(2) hypobranchial, 8(2) ceratobranchial, 1(2) on cartilage between ceratobranchial and epibranchial, and 5(1) or 6(1) epibranchial gill-rakers.Branchiostegal rays 4(2), three originating on anterior ceratohyal and one on posterior ceratohyal.Adipose fin with proximally well-delimited dark area (Fig. 1).
Color in life.Ground color of dorsal portion of body yellow to greenish, with iridescent midlateral yellow stripe and large, dark, ventrally curved longitudinal stripe immediately ventral to it, stripe extending from humeral region to caudal peduncle.
Abdominal region white to light yellow.Eye bright green.
Middle caudal-fin rays with dark mark, anteriorly delimited by dorsal and ventral yellowish areas (Fig. 2).
Etymology.From the Greek chloros, meaning green, and ophthalmos, meaning eye, in reference to the iridescent green eyes in live specimens.An adjective.
Color in life.Ground color yellowish, with distinct clear midlateral yellow stripe and large, dark, ventrally curved longitudinal stripe immediately ventral to it.Stripes run from humeral region to caudal peduncle.Abdomen white to light yellow.Eye clear, with longitudinal dark stripe.Caudal fin with middle dark stripe delimited anteriorly by upper and lower yellowish areas.Specimens kept in captivity for several months have dorsal and anal fins lightly pigmented with gradients of green, yellow and red (Fig. 7).Etymology.From the Latin plumbum, meaning lead, in allusion to the color of the midlateral stripe below the unpigmented stripe in live specimens.An adjective.
Distribution.Known from headwaters of tributaries of the rio Braço Norte (rio Tapajós basin) in the Serra do Cachimbo (Figs. 4 and 5).osteological characters for grouping M. levidorsa, M. sanctaefilomenae, M. oligolepis, M. cotinho, and M. grandisquamis.Those expansions are variably developed in the two new species described herein, M. petymbuaba and all other species of Moenkhausia examined (see "examined material").Thus, such a range of variation of those characters may constitute synapomorphies for a broader group within Moenkhausia.
As discussed by Lima & Zuanon (2004), the dark midlateral stripe in small characids can be categorized (without implied homology) as narrow and straight (e.g., Hyphessobrycon cachimbensis Travassos and Moenkhausia petymbuaba); broad and straight (e.g., Moenkhausia phaenota Fink, and Moenkhausia heicoi Géry & Zarske), or broad and curved (e.g., Nematobrycon and Inpaichthys).Moenkhausia plumbea and M. clorophthalma have a broad and ventrally curved dark midlateral stripe somewhat similar to Nematobrycon and Inpaichthys except in being more diffuse.Mirande (2009) recently criticized the uncritical acceptance of the taxonomic scheme for characids, based on Eigenmann's (1917) criteria and perpetuated by Géry (1977).Although a few species of Moenkhausia were included in Mirande's phylogenetic study, both analyses performed by the author refute the monophyly of the genus.In the weighted parsimony hypothesis, Moenkhausia is paraphyletic, with Bario as sister taxon to M. sanctaefilomenae, occupying the distalmost position in the clade.In the unweighted hypothesis, the species of Moenkhausia are recovered in two clades included in a large policotomy, with M. sanctaefilomenae as the sister taxon of Bario in one of the clades, corroborating Benine (2004).However, the synapomorphies of this and all the clades located distally to node 203 (except node 220, the "Jupiaba clade") are not listed in his appendix 3, due to a composition error in the final version of the manuscript (Mirande, pers. comm.).Our examinations suggest that Moenkhausia clorophthalma and M. plumbea appear to be closely related to M. petymbuaba based on the shared presence of dark blotches on the base of body scales.Nevertheless, the relationships between these species and congeners are obscure, and the group proposed herein does not conform to any previously proposed species group within the genus.
The discovery of related species of Moenkhausia endemic to tributaries of both the rio Xingu and rio Tapajós basins on the highest portion of the Serra do Cachimbo highlights the complexity of the river drainages in the area.Apparently, M. clorophthalma, M. petymbuaba and M. plumbea have rather restricted distributions, and do not occur sympatrically.This scenario indicates that the increase in collection efforts, especially in similar creeks of isolated drainages, may result in the discovery of additional endemic species of Moenkhausia and other genera.

Discussion
Even though the monophyly of Moenkhausia is yet to be demonstrated, the species described herein display the features proposed by Eigenmann (1917) to define that genus.Among their congeners, M. chlorophthalma, M. plumbea, and M. petymbuaba are the only species with a color pattern composed of large dark blotches on the scales of seven to nine dorsalmost longitudinal scale series.Pigmented scales are also observed in species currently assigned to the M. oligolepis/M.sanctaefilomenae group and M. diamantina.However, in those species, the pigmentation is concentrated on the distal border of the scales, thereby forming a dark reticulate pattern on the body.Benine (2002) states that M. nigromarginata also has a reticulate pattern, but Costa (1994) did not consider the species as demonstrating this feature.Examination of type specimens of M. nigromarginata similarly failed to confirm Benine's (2002) observation.Moenkhausia cotinho, which was nested within the M. oligolepis/M.sanctaefilomenae group by Benine (2002), also has blotches at the bases of the scales, but differs from M. chlorophthalma, M. plumbea, and M. petymbuaba by having small dark patches on the third and fourth longitudinal series above the lateral line, and having a reticulate pattern on the scales below the lateral line series.Benine (2002) proposed the presence of laminar expansions of the ectopterygoid and the palatine as derived

Table 1 .
Morphometric data of Moenkhausia chlorophthalma.N = 31, SD = standard deviation.spine of 17 th (2) vertebra.Caudal-fin forked, lobes slightly rounded, similar in size.Principal caudal-fin rays i,9+8,i.Ground color tan, with chromatophores densely covering entire body, except for ventral portion.Lower lip, snout, top of head and dorsal portion of body darkly pigmented, resulting in overall countershaded color pattern.Edge of upper lip dark.Inconspicuous humeral blotch present, vertically elongated.Seven dorsalmost longitudinal scale rows with scales bearing large dark blotches anterior to center of each, with blotch fading towards scale border.Longitudinal, broad, dark midlateral stripe slightly curved ventrally, extending from pectoral girdle to tip of middle caudal-fin rays.Stripe diffuse, formed by scattered chromatophores.Dorsal, caudal, anal, and pectoral fins hyaline, with small scattered chromatophores.

Table 2
convex from upper lip to vertical through nares; somewhat straight from latter point to tip of supraoccipital spine; convex from tip of supraoccipital spine to dorsal-fin origin, straight from dorsal fin terminus to adipose fin; slightly concave between latter point and origin of anteriormost dorsal procurrent caudal-fin ray.Ventral profile of head and body distinctly convex from lower lip to pelvic-fin origin; straight from latter point to anal-fin origin, and