A new species of Hyphessobrycon Durbin ( Characiformes : Characidae ) from the rio Juruena basin , Central Brazil , with notes on H . loweae Costa

A new species of Hyphessobrycon, H. peugeoti, is described from the middle portions of the rio Juruena drainage, upper rio Tapajós basin, Mato Grosso State, Brazil. It can be distinguished from all congeners, with the exception of H. loweae and H. heliacus, by a filamentous elongation of the dorsal fin and the approximately straight margin of the anal fin in adult males. It can be distinguished from both H. loweae and H. heliacus by an overall red coloration in life (vs. a golden coloration in life in the latter). Additionally, it can be distinguished from H. heliacus by the lack of chevron-like dark markings along the midline (vs. presence of chevron-like dark-markings in H. heliacus), and from H. loweae by the presence of only five horizontal scale rows between the dorsal-fin origin and the lateral line (vs. 6-7 in H. loweae), and the higher number of branched anal-fin rays (21-24, modally 22, vs. 17-21, modally 20, in H. loweae). Additional meristic, morphometric, and distributional data are provided for Hyphessobrycon loweae, including its first record in the rio Araguaia/Tocantins basin. Comments on a putative monophyletic group including H. peugeoti, H. loweae, H. heliacus, H. elachys, and H. moniliger are presented.

Collecting activities undertaken in the last few years in the rio Juruena (which along with the rio Teles Pires, forms the rio Tapajós) revealed a distinctive pretty Hyphessobrycon species with an overall reddish color pattern and a greatly elongated dorsal fin in adult males.This species closely resembles and is putatively related to H. loweae Costa & Géry, described from the upper rio Xingu basin in Brazil.The purpose of the present study is to describe the new species, and to provide additional information on the diagnosis and distribution of H. loweae.

Material and Methods
Counts and measurements were taken according to Fink & Weitzman (1974) and Menezes & Weitzman (1990), except for the number of horizontal scale rows below the lateral line, which were counted to the pelvic-fin insertion.The number of horizontal scale rows between dorsal-fin origin and lateral line does not include scales of the median predorsal series situated just anterior to first dorsal-fin ray.In the descriptions, the frequency of each count is given in parentheses after the corresponding count.An asterisk indicates counts of the holotype.Counts of supraneurals, vertebrae, procurrent caudal-fin rays, unbranched dorsal-and anal-fin rays, branchiostegal rays, gill-rakers, and dentary teeth were taken from cleared and stained paratypes (c&s), prepared according to Taylor & van Dyke (1985).Vertebrae of the Weberian apparatus were counted as four elements and included in the vertebral counts, and the compound caudal centrum (preural 1 + ural 1; Fink & Fink, 1981) was counted as a single element.Institutional abbreviations are as follows: ANSP, Academy of Natural Sciences of Philadelphia, Philadelphia; MNRJ, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro; MZUSP, Museu de Zoologia da Universidade de São Paulo, São Paulo; and ZUEC, Museu de Zoologia da Universidade Estadual de Campinas "Adão José Cardoso", Campinas.Specimens are grouped by state and hydrographic drainage and ordered from North to South in the lists of examined specimens.

Color in alcohol.
Ground color pale to light yellowish.Guanine pigmentation present on opercular and infraorbital series, and on few scales in some specimens.Body covered by scattered dark chromatophores, except at ventral regions of head and abdomen, which are clear.Dorsal surface of head and body, from snout to caudal fin, presenting dense concentration of dark chromatophores.Humeral region with vertically elongated, roughly rectangular dark blotch, tapering ventrally, at level of second and fourth lateral line scales.Blotch one and half scales wide, three to three and half scales high.Narrow midlateral stripe formed by chromatophores at myosepta between hypaxial and epaxial bundles of muscles, more conspicuous posteriorly to dorsal-fin base.Dark chromatophores distributed along myomeres junctions forming chevron marks, except at region immediately above anal-fin base, where dark chromatophores are uniformly scattered.Caudal peduncle blotch black, widely expanded in larger specimens, forming broad rectangular blotch occupying entire caudal peduncle surface.Dorsal, adipose, and caudal fins with considerable amount of dark chromatophores, imparting overall dark coloration to these fins.Dark chromatophores of dorsal fin more concentrated over its apical portion.Pectoral and pelvic fins hyaline, with few, scattered dark chromatophores.Anal fin hyaline, with some scattered dark chromatophores on interradial membranes.

Color in life.
Based on photograph of freshly collected holotype (Fig. 4).Top of head and dorsal portion of body dark red.Lateral and ventral portions of body silvery, suffused with red  chromatophores which impart overall carmine red coloration.Dorsal, pectoral, pelvic, and anal fins carmine red.Caudal peduncle blotch dark.Caudal fin hyaline, with some diffuse dark and reddish pigmentation.Female coloration in life not recorded.
Sexual dimorphism.Adult males of Hyphessobrycon peugeoti are readily discernible from females by presenting an elongation of the dorsal fin that becomes filamentous, reaching, when depressed, the caudal-fin basis in fully grown specimens, and an approximately straight margin, and thickened rays in the anal fin.This fin morphology contrasts with the normally developed dorsal fin and the lobed anal fin of females (compare Figs. 1 and 2).The caudal peduncle blotch is also more developed in adult males.These dimorphic features are also found in H. heliacus and H. loweae.Fin hooks, a common feature of mature characid males (Malabarba & Weitzman, 2003) are absent (see Discussion, below).
Habitat and ecological notes.Specimens of Hyphessobrycon peugeoti was collected in shallow areas (less than 1 m deep) in the early dry season.The type locality of H. peugeoti was a swampy deforested area, alongside a detour of road MT-208 (old road BR-80) immediately downstream from a preserved tract of native forest; the water flow was choked with grasses and small shrubs.Sample MNRJ 29609 was collected downstream where the stream crossed the dry and muddy bottom of a dam that was burst open by heavy rains about two months earlier.The single specimen MNRJ 29503 was collected in a flowing stream with sandy bottom, transparent water, and poorly-developed aquatic vegetation.Paratypes ANSP 190999, MZUSP 77734, and ZUEC 6362 were collected in a flooded area adjacent to the rio Juruena.
Etymology.Hyphessobrycon peugeoti is patronymic to the Peugeot family, who invented the Peugeot pepper mill mechanism in 1842 and whose manufacturing business led to the establishment of a carbon sink reforestation project in the fazenda São Nicolau, in central Brazil, and eventually to the discovery of this new species.dark chromatophores.Anal fin hyaline, with some scattered dark chromatophores over its interradial membranes.

Color in life.
Based on photographs of two mature males (MZUSP 97435, one depicted in Fig. 9), and the holotype (Costa & Géry, 1994: 72, fig.1), and cursorial examination in the field of freshly collected specimens from lots MZUSP 97435 and MZUSP 95611 by the second author.Overall coloration (including all fins) golden-yellow; some specimens presenting a large amount of silvery pigmentation, apparently a consequence of infestation by trematodes ("brass-tetras"; cf.Géry & Delage, 1963).Upper portion of eye red.
Sexual dimorphism.Hyphessobrycon loweae presents the same type of sexual dimorphism as observed in H. peugeoti, i.e., mature males with an elongated, filamentous dorsal fin, anal fin with all fin rays with approximately the same size and relatively enlarged, resulting into a straight fin margin, and a more developed caudal-fin blotch.As in Hyphessobrycon peugeoti, mature males of H. loweae lack fin hooks.
Habitat and ecological notes.Hyphessobrycon loweae inhabits streams with clear water, slow current and abundant submerged vegetation.This is the type of habitat found at the type locality, the córrego Xavante (C.R. Moreira, pers. comm.;Costa & Géry, 1994), as well as at the upper rio das Mortes (J.L. Birindelli, pers.comm.) and tributaries of the rio Culuene at Gaúcha do Norte (F. C. T. L., pers.obs.)."Lago do Leo" at the rio Suiazinho, where some paratypes of Hyphessobrycon loweae were collected, is a small lake with dense aquatic vegetation (Lowe-McConnell, 1991: 71).
Distribution and biogeography.Hyphessobrycon loweae was originally described from tributaries of the rio Culuene and rio Suiá-Missú in the upper rio Xingu basin, Mato Grosso, Brazil.The species is herein recorded from the upper rio das Mortes, a tributary of the rio Araguaia-Tocantins basin (Fig. 5).The species is known from adjacent (less than 20 km apart) headwaters of the rio Culuene and rio das Mortes, and presumably may have been transposed across the water divide via stream capture events.Several fish species are known to occur in adjacent river systems across the southern tributaries of the Amazon basin flowing through the Brazilian shield, presumably due to river capture events resulting from neotectonic reactivation of ancient faults of the Transbrasiliano lineament, which transverses the region (Lima & Ribeiro, 2011).

Remarks. Comparisons between Hyphessobrycon loweae
specimens from the rio Culuene (rio Xingu basin) and rio das Mortes (rio Tocantins-Araguaia basin) did not reveal any features that might distinguish these different populations, and thus they are herein considered to represent a single species.The vertically-elongated, curved dark bars in the posterior portion of body (Fig. 7) are present in some mature male specimens from both the rio das Mortes (MZUSP 101404) as well as from the rio Culuene (MZUSP 95611) drainages.

Discussion
As remarked in the Introduction, the genus Hyphessobrycon does not constitute a monophyletic entity.Pending further studies on the phylogenetic relationships of Hyphessobrycon and related genera, the new species described herein is provisionally assigned to this genus, following the traditional diagnosis of the genus.Based on the color pattern, Géry (1977) distinguished six admittedly artificial species groups within the genus.One of these groups, referred to as "Hyphessobrycon callistus-group" by Géry (1977), partly corresponds to the "rosy tetra clade", hypothesized by Weitzman & Palmer (1997) to be a monophyletic entity.Hyphessobrycon loweae was listed among the species considered by Weitzman & Palmer (1997: 223) as being "possible rosy tetras", probably due to the elongation of the dorsal fin in mature males, a feature shared with some species of the group, such as H. bentosi (Durbin), H. epicharis Weitzman & Palmer, and H. erythrostigma (Fowler) (Weitzman & Palmer, 1997).However, the elongation of the dorsal fin in H. loweae, as well as in H. elachys, H. heliacus, and H. peugeoti is formed by the extreme extension of the last unbranched, and two or three anteriormost branched dorsal-fin rays, forming a filamentous prolongation in fully mature males.This contrasts with the condition found in species belonging to the rosy tetra clade, such as H. bentosi, H. epicharis, and H. erythrostigma, in which the last unbranched and the anteriormost four branched dorsal-fin rays, though elongated, are not considerably longer than the remaining dorsal-fin rays, and are not long enough to form a filamentous prolongation (Weitzman, 1977;Weitzman & Palmer, 1997).Although Moreira, Landim & Costa (2002: 431) stated that H. loweae does not possess a filamentous dorsal fin, fully mature males of the species do have this condition (Figs. 6 and 9).We consider this condition as nonhomologous to that found in H. erythrostigma and related species within the "rosy tetra clade" and reject the hypothesis of a close relationship between H. loweae and the species of that clade.
In most species of Hyphessobrycon and other tetras the posteriormost unbranched and the anteriormost branched anal-fin rays are more elongate than the remaining rays, forming a pointed, generally short, anterior fin lobe.The anal-fin rays of mature males of a few species of Hyphessobrycon, however, have approximately the same size, forming a straight margin.Within the genus this unusual condition is only known in H. bifasciatus, H. heliacus, H. loweae, and H. peugeoti.Mature males of H. bifasciatus are distinct in possessing numerous small hooks along the anal-fin rays.Hooks are absent in H. heliacus, H. loweae, and H. peugeoti mature males, suggesting that H. bifasciatus is closely related to other tetras with sexual hooks in the anal fin.In fact, in Mirande's (2010) phylogenetic hypothesis of the family Characidae, H. bifasciatus belongs to the Hyphessobrycon luetkenii clade and is closely related to the Astyanax clade, both clades composed almost exclusively by species displaying bony fin hooks.Mature males of H. heliacus, H. loweae, and H. peugeoti share a large, elongated dark blotch on the caudal peduncle, which extends across most of caudal peduncle's surface, including its upper and lower portions in H. loweae and H. peugeoti.As remarked by Moreira, Landim & Costa (2002), mature males of H. elachys also possess a similar broad dark blotch on the caudal peduncle, which typically extends into the middle caudal-fin rays.Hyphessobrycon elachys was considered by Moreira, Lima & Costa (2002) as related to H. moniliger Moreira, Lima & Costa due to the shared, derived condition of the anal fin in mature males, which presents a well-defined, rounded lobe formed by thickened anal-fin rays, and upwarddirected projections on the proximal portion of the anal-fin rays (Moreira, Lima & Costa, 2002: 78-79, figs. 4-5).Hyphessobrycon moniliger also possesses a welldeveloped caudal peduncle blotch in mature males, though not as developed as in the aforementioned species (Moreira, Lima & Costa, 2002: 78).In spite of the similarities of anal-and dorsal-fin morphology and caudal-peduncle pigmentation in mature males, Moreira, Landim & Costa (2002: 431-432) considered that accepting the monophyly of a group encompassing H. elachys, H. heliacus, and H. loweae would be premature at that time and that more studies on the phylogenetic relationships of Hyphessobrycon were needed to adequately address the issue.Although we understand the reasoning which prompted that cautionary note, the sum of similarities of anal-and dorsal-fin morphology and caudal-peduncle pigmentation shared by mature males of H. elachys, H. heliacus, H. loweae, H. moniliger, and H. peugeoti suggests a close relationship among these species.
Hemigrammus filamentosus Zarske was described from specimens from the aquarium hobby said to have been collected at the rio Araguaia basin in Brazil.Hemigrammus filamentosus is distinctive in possessing the first anal-fin rays elongated, a feature not observed in any of the aforementioned species.Zarske (2011) considered He.filamentosus as possibly related to He. taphorni Benine & Lopes, due to the elongation of the dorsal fin in the latter.However, the elongation of the dorsal fin in He. taphorni apparently does not present the ribbon-like aspect present in He. filamentosus, Hyphessobrycon elachys, Hy. heliacus, Hy. loweae, and Hy.peugeoti, although this is an inference since the dorsal fin of the holotype of He. taphorni is not perfectly preserved (Benine & Lopes, 2007: fig.1).On the other hand, the dorsal fin in mature males of He. filamentosus is as elongate as in Hy. elachys, Hy. heliacus, Hy. loweae, and Hy.peugeoti, and the pelvic fins are elongated and similar to the pelvic fins of Hy. elachys and Hy.heliacus.Hemigrammus filamentosus and, perhaps, He. taphorni may belong to a monophyletic clade encompassing species currently assigned to the genera Hyphessobrycon and Hemigrammus, possessing sexually dimorphic males with modified fins.A proper evaluation of this hypothesis, however, will have to await a broader phylogenetic analysis encompassing species currently assigned to Hyphessobrycon, Hemigrammus and related genera, a task which has become more feasible after the recent publication of a phylogenetic analysis of the Characidae by Mirande (2010).

Table 1 .
Morphometric data of Hyphessobrycon peugeoti new species from rio Juruena drainage, based on holotype (MNRJ
Diagnosis.Hyphessobrycon loweae can be distinguished from all congeners, with the exception of H. elachys, H. heliacus, and H. peugeoti, by the conspicuously elongated and filamentous dorsal fin in mature males (vs.dorsal and pelvic fins, when elongated, never filamentous).Hyphessobrycon loweae can be distinguished from H. elachys and H. peugeoti by its overall golden color in life (vs.a general clear/silvery color in H. elachys, and reddish color in H. peugeoti).Hyphessobrycon loweae can be distinguished from H. heliacus by the shorter pelvic-fins in fully mature males, reaching only the first anal-fin branched ray (vs.pelvic-fins filamentous, reaching up to the sixth anal-fin branched ray in H. heliacus), and by lacking chevron-like dark markings along the midline (vs.chevron-like dark markings along the midline present in H. heliacus).Additionally, H. loweae can be distinguished from H. elachys by possessing an anal fin with a straight margin in mature males (vs. a distinctly rounded anal-fin lobe present in H. elachys mature males); and from H. peugeoti by possessing a higher number of horizontal scale