Rio Juruena Research Articles

Phylogenetic relationships, distribution, and conservation of Roosmalens' dwarf porcupine, Coendouroosmalenorum Voss & da Silva, 2001 (Rodentia, Erethizontidae).

The New World porcupines of the genus Coendou comprise 16 species of arboreal nocturnal rodents. Some of these species are poorly known and have not been included in phylogenetic analyses. Based on recently collected specimens with associated tissue from the Brazilian Amazonia, we investigate the distribution and phylogenetic relationships of Roosmalens' dwarf porcupine, Coendouroosmalenorum, using an integrative approach using mitochondrial gene sequences and morphological data from new specimens and localities. Our results recovered C.roosmalenorum in the subgenus Caaporamys. However, analyses of our molecular and combined datasets produced different topologies. The new record shows the presence of C.roosmalenorum 480 km to the southeast of the Rio Madeira and 95 km away from Rio Juruena in Mato Grosso state, indicating a wider distribution in southern Amazonia than suspected. All known records of C.roosmalenorum are in the Madeira biogeographical province, to which it might be endemic.

On a new colorful species of Moenkhausia (Characiformes: Characidae) from the upper rio Madeira basin at the Chapada dos Parecis, Brazil, with comments on its conservation and putative biogeographic history.

A new species, Moenkhausia iris, is described from the upper rio Madeira basin, Mato Grosso State, Brazil. The new species is unique among congeners by its color in life, which is the dorsal half of body blue or green and ventral half red, more intense above the anal fin. Additionally, it can be distinguished by having a single, vertically elongated humeral spot, a lateral surface of body, caudal peduncle, and anal fin without distinct blotches or oblique marks and 18-19 branched anal-fin rays. The new species is endemic from a small tributary of the Rio Guaporé, rio Madeira drainage at Chapada dos Parecis. Its putatively close relatives are endemic to the upper rio Juruena located at the same shield. Both headwaters are very close to each other, sharing other restricted range species, and their hydrogeological topography indicates the upper rio Juruena stretch was captured by the rio Guaporé through a headwater capture event. Moenkhausia iris is much appreciated in the international aquarium trade, as well as many other tetras endemic from the same area. Exportation is based on the capture of wild individuals so sustainable exploitation is necessary for its conservation.

A new rheophilic species of Knodus Eigenmann (Characiformes: Characidae: Stevardiinae) from the upper rio Juruena, rio Tapajós basin, Chapada dos Parecis, Mato Grosso, Brazil

Knodus ytuanama, new species, is described from the upper rio Juruena, rio Tapajós drainage, Amazon basin, Mato Grosso, Brazil. The new species differs from its congeners by presenting the interradial membranes of the caudal fin thickened, forming folds, and also differs from most congeners by the presence of a dark, wide midlateral stripe extending from the posterior margin of opercle to the middle caudal-fin rays, the absence of a humeral blotch in adults, and by having four rows of scales between the lateral line and the pelvic-fin origin, among another features. We also provide a discussion on the presence of membranous flaps on the fins as an adaptation for living in fast-water environments in Knodus ytuanama n. sp. as well as in a congener, K. tiquiensis.

The emerald green tetra: a new restricted-range Hyphessobrycon (Characiformes: Characidae) from the upper rio Juruena, Chapada dos Parecis, Brazil

ABSTRACT A new species of Hyphessobrycon is described from the rio Mutum, a tributary of the rio Juruena, rio Tapajós basin, Brazil. The new taxon can be distinguished from its congeners by the presence of a well-defined and relatively narrow dark midlateral stripe on body, extending from head to the middle caudal-fin rays, presence of a humeral blotch, distal profile of the anal fin falcate in males, 13-16 branched anal-fin rays (vs. 17-26), and 11 or 12 horizontal scale rows around caudal peduncle. The new species shows polymorphism regarding the presence of the adipose fin, and a discussion on this type of polymorphism across the family and its systematic implications is presented.

Moenkhausia andrica (Characiformes: Characidae): a new species from the rio Tapajós basin, Brazil, with minute fin hooklets in females.

In this study, a new species of Moenkhausia is described from the upper rio Juruena, rio Tapajós basin, Brazil. It is distinguished from all congeners by the presence of minute bony hooks in all fins of both mature females and males and combination of a prepelvic region flattened, dorsal portion of the humeral blotch extending two scales horizontally and vertically, lateral line with 28-32 scales, five scale series above and below lateral line; circumpeduncular scales 13-14, anal-fin rays 16-19 and dorsal portion of eyes blue in live specimens. The new species is also supported by high divergence in the mitochondrial gene cytochrome c oxidase subunit I (COI). The presence of minute fin bony hooks in both females and males, population variations and late development of the lateral line in Moenkhausia andrica are discussed.

A new species of Amazonian bluntnose knifefish Brachyhypopomus (Gymnotiformes: Hypopomidae), with comments on its phylogenetic position

A new species of the bluntnose knifefish genus Brachyhypopomus Mago-Leccia is described from headwaters of upper Rio Juruena, and upper Rio Machado, Amazon basin, Brazil. The new species differs from all congeners by the absence of a small independent ossification of the Weberian complex located posterodorsally to the supraoccipital. It can be additionally distinguished from its congeners by a set of characters in combination that includes: absence of accessory electric organ over the opercular region, absence of a prominent pale uninterrupted middorsal stripe on body, presence of scales on the entire middorsal region of body, dorsal rami of the recurrent branch of anterior lateral-line nerve not externally visible, presence of a dark suborbital stripe, and possession of 8–10 scale rows above the lateral line. The phylogenetic position of the new species is inferred by its inclusion in a total-evidence matrix with data from morphology, mitochondrial genes, and nuclear genes of all species. The new species is apparently restricted to upland tributaries of the Chapada dos Parecis, more than 500 m high. Comments on the occurrence of fish species in multiple independent basins at Chapada dos Parecis are also provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:620C58EB-4DA7-4322-9E2D-ACF4152DB0C7

A new rheophilic South American darter (Crenuchidae: Characidium) from the rio Juruena basin, Brazil, with comments on morphological adaptations to life in fast-flowing waters.

Characidium iaquira, a new species from the upper rio Juruena, rio Tapajós basin, Brazil, is described. The new species can be promptly distinguished from all congeners by having a unique v-shaped dark mark lying along the caudal-fin extension, in medium- and large-sized specimens, and a remarkable iridescent green colouration in life. Characidium iaquira is closely related to Characidium crandellii and Characidium declivirostre by sharing unambiguous synapomorphies such as branchiostegal membranes united to each other across the isthmus, a scaleless area extending from the isthmus to the pectoral girdle, and dermal flaps surrounding anterior and posterior naris independent, but touching each other distally. Morphological specializations of the paired fins in the three riffle-dwellers species are discussed, including the wing-like shape, robustness, and inclination of the pectoral fin.

A new Corydoras (Ostariophysi: Siluriformes: Callichthyidae) with an unusual sexual dimorphism from the rio Juruena basin, Brazil.

A new Corydoras is described from the rio Juruena system, upper rio Tapajós drainage, Amazon basin, Brazil. The new Corydoras is distinguished from all congeners by presenting a combination of a conspicuous broad vertical dark bar on head, at the level of the eye (mask), an overall light background color without large blotches or stripes on body or fins, the presence of two to four small dark blotches along the midline, and pectoral spine with antrorse serrations on its posterior margin. Males of the new species possess numerous, well-developed odontodes over the lateral portions of head, pectoral girdle, and pectoral spines, an uncommon feature for the genus. The new species is hypothesized to belong, within the genus Corydoras, either to Lineage 6 or Lineage 9.

A new species of Eigenmannia Jordan & Evermann (Gymnotiformes: Sternopygidae) from rio Tapajós, Brazil, with discussion on its species group and the myology within Eigenmanniinae.

A new species of Eigenmannia is described from the rio Mutum, tributary of upper rio Juruena, rio Tapajós basin, Comodoro, Mato Grosso, Brazil. The new species is distinguished from all congeners by coloration pattern, position of the mouth, number of scales rows above lateral line, number of premaxillary and dentary teeth, number of precaudal vertebrae, orbital diameter, mouth width, relative depth of posterodorsal expansion on infraorbitals 1+2 and relative size of coronomeckelian bone. Comments on potentially useful characters in phylogenetic studies derived from musculature, discussion on Eigenmannia species-group and the first dichotomous key for Eigenmannia are provided.

Hemiodus bimaculatus, a new species of Hemiodontidae from the Rio Tapajós drainage, Brazil (Ostariophysi: Characiformes).

Hemiodus bimaculatus sp. nov., is described from tributaries of the Rio Juruena and Rio Teles Pires in the upper Rio Tapajós basin. The new species is diagnosed from most congeners, except Hemiodus jatuarana, by having a conspicuous circular or horizontally elongate dark blotch on the caudal peduncle (v. inconspicuous in H. iratapuru and absent in the other species). The new species differs from H. jatuarana by having a round midlateral spot on the flank (v. absent in H. jatuarana), 98-121 perforated scales in the lateral line (v. 66-72 in H. jatuarana), 23-28 scale series above and 14-19 below lateral line (v. 12-13 above and 6-7 below in H. jatuarana). Hemiodus bimaculatus is hypothesised to be related to species of the H. microlepis group, from which it also differs by having 11-25 epibranchial (v. 26-34 in H. argenteus, 29-39 in H. microlepis, 21-42 in H. orthonops and 27-35 in H. parnaguae) and 18-31 ceratobranchial (v. 38-50 in H. argenteus, 43-58 in H. microlepis, 32-52 in H. orthonops and 34-48 in H. parnaguae) gill rakers in the first arch.

A new species of Bryconops (Characiformes: Iguanodectidae) from the Rio Tapajós basin, Brazil.

A new species of Bryconops is described from upper rio Juruena drainage, rio Tapajós basin, Amazon basin, state of Mato Grosso, Brazil. The new species is hypothesized as belonging to the subgenus Creatochanes by presenting the posterior extension of maxilla reaching to the junction of second and third infraorbital bones, and the ventroposterior margin of second infraorbital forming a complete border with third infraorbital, resulting in the lack of a naked area between them. The new species is easily distinguished from other species of the subgenus Creatochanes by the color pattern of the caudal fin, which consists of the dorsal lobe conspicuously dark pigmented on its distal half and the ventral lobe dark gray pigmented along its ventral portion below the horizontal through the ventral margin of the caudal peduncle.

New remarkable sexually dimorphic miniature species of Hyphessobrycon (Characiformes: Characidae) from the upper Rio Tapajós basin.

A new miniature species of Hyphessobrycon is described from an affluent of the Rio Papagaio, tributary of the Rio Juruena, upper Rio Tapajós basin, Mato Grosso State, Brazil. The new species can be distinguished from its congeners by having a remarkable secondary sexual dimorphism in its live colouration (males are red and females yellow), well-defined and relatively narrow dark midlateral stripe extending from tip of snout to tip of middle caudal-fin rays, absence of humeral blotch, 15-18 branched anal-fin rays and five or six branched pelvic-fin rays. The sexually dimorphic colouration of the new species is briefly discussed regarding its temporal variation.

Crenicichla ploegi, a new species of pike-cichlid of the C. saxatilis group from the Rio Juruena and upper Rio Paraguai basins in Brazil, with an updated diagnosis and biogeographical comments on the group (Teleostei: Cichlidae).

Crenicichla ploegi, new species, is described based on material from the Rio Juruena (Rio Papagaio, Rio do Sangue, Rio Arinos, and Rio Juruena itself) and from tributaries of the upper Rio Paraguai (upper Rio Jauru, upper Rio Cabaçal and upper Rio Sepotuba) in Mato Grosso, Brazil. Crenicichla ploegi is the twenty-third species of the C. saxatilis group. It is distinguished from all other species of the group by the presence of dark spots and vermiculations on snout, interorbital area and dorsally on head in adults vs. dark markings absent or present only in juveniles but absent in adults, and by the presence of a deep and strongly pigmented lateral band present in both juveniles and adults, occupying a depth of 4-6 horizontal scale rows vs. lateral band narrower, occupying a depth of 2-3 horizontal scale rows, and conspicuous only in juveniles and smaller specimens, faded or absent in larger specimens. Diagnostic characteristics of the C. saxatilis group proposed in previous studies were discussed to update the diagnosis of the group, and morphological comparisons among the species included in the group, with biogeographical comments, are provided. The presence of conspicuous dark markings dorsally on the head and the presence of a prominent midlateral band are hypothesized to be paedomorphic characteristics, retained from juvenile conditions in the context of the species of the C. saxatilis group.

Thayeria tapajonica (Characiformes: Characidae), a new species from rio Tapajós basin, Brazil.

A new species of penguin tetra, Thayeria tapajonica, is described from the rio Tapajós basin. It is most similar to T. boehlkei by presenting a straight midlateral stripe running anteriorly to immediately posterior to the head, while in T. ifati and T. obliqua the midlateral stripe is restricted to the caudal peduncle, merging with an anterodorsal oblique stripe. The new species is restricted to the rio Tapajós basin downriver of the confluence of the rio Juruena and rio Teles Pires, and lower rio Teles Pires, where its distribution overlaps with T. boehlkei.

A new sexually dichromatic miniature Hyphessobrycon (Teleostei: Characiformes: Characidae) from the Rio Formiga, upper Rio Juruena basin, Mato Grosso, Brazil, with a review of sexual dichromatism in Characiformes.

Hyphessobrycon myrmex sp. nov., is described from the Rio Formiga, upper Rio Juruena, upper Rio Tapajós basin, Mato Grosso, Brazil. The new species can be distinguished from congeners by having the lower half of the body deeply pigmented with dark chromatophores, chromatophores concentrated above the anal fin and forming a broad, diffuse, dark midlateral stripe and by having a dense concentration of dark chromatophores along unbranched dorsal-fin rays and distal portions of the two or three subsequent branched rays. In life, H. myrmex exhibits a conspicuous sexual dichromatism, with adult males red to orange and females and immatures pale yellow. A list containing 108 sexually dichromatic taxa in six families of Characiformes is provided and the distribution of this poorly known type of dimorphism across the Characiformes is discussed.

A new genus of Neotropical rheophilic catfishes, with four new species (Teleostei: Siluriformes: Pseudopimelodidae)

ABSTRACT Rhyacoglanis, a new genus of the South American freshwater catfish family Pseudopimelodidae is described from cis-Andean portions of the continent. Rhyacoglanis is distinguished from other genera of the family by three synapomorphies: presence of a light blotch on the cheek; a connection between the middle of the dark caudal-fin stripe and the dark caudal-peduncle pigmentation; and 30-35 total vertebrae. Species of Rhyacoglanis are rheophilic and strongly associated with rapids and other swift-flowing waters. A phylogenetic analysis based on 41 morphological characters yields a hypothesis of monophyly of the Pseudopimelodidae and Rhyacoglanis. Pimelodus pulcher Boulenger, 1887, from the western Amazon basin is designated as type-species of the new genus and redescribed. Four new species are described: Rhyacoglanis annulatus, from the río Orinoco basin, with a nearly ringed dark band on the caudal peduncle, and a larger distance between anus and anal-fin origin; R. epiblepsis, from the rio Madeira basin, with numerous dark spots scattered on the body, and rounded caudal-fin lobes; R. paranensis, from the upper rio Paraná basin, with three distinct dark bands on the body, and 31-33 total vertebrae; and R. seminiger, from the rio Juruena basin, with subdorsal and subadipose dark bands fused anteroposteriorly, and a separate dark band on the caudal peduncle.

A new Otocinclus (Siluriformes: Loricariidae: Hypoptopomatinae) from the Rio Juruena Basin, central Brazil.

A new species of Otocinclus (Loricariidae) is described from the Rio Juruena, a right bank tributary of the Rio Tapajós system in Mato Grosso State, central Brazil. The new taxon can be distinguished from its congeners by the possession of an ocular operculum and by a complete lateral line. Additionally, the new species is distinguished by having a dorsal trunk coloration composed of a set of distinct oval dark blotches and by a caudal spot.

Description of a New Species ofMoenkhausia(Characiformes, Characidae) from the Upper Rio Tapajós Basin, Brazil

A new species of Moenkhausia is described from the upper Rio Juruena, Rio Tapajos basin, Mato Grosso, Brazil. The new species is diagnosed from all congeners, except M. eurystaenia, M. heikoi, and M. phaeonota, by the presence of a dark, straight, broad stripe extending from the opercle to the middle caudal-fin rays. The new species can be distinguished from M. heikoi and M. phaeonota by having 18–20 branched anal-fin rays and from M. eurystaenia by having a narrow longitudinal dark line along the horizontal septum, starting at the vertical through the pelvic-fin origin. The presence of a conspicuous dark blotch on the ventral portion of the opercle and on the ventral portion of the vertical arm of the preopercle is also useful to distinguish the new species from most congeners.

A New Species ofHyphessobrycon(Characiformes: Characidae) from the Upper Rio Juruena Basin, Central Brazil, with a Redescription ofH. cyanotaenia

A new species of Hyphessobrycon is described from the Rio Papagaio, a tributary of the Rio Juruena, Rio Tapajos basin, Brazil. The new taxon can be distinguished from its congeners by having a well-defined and relatively narrow dark midlateral stripe on body extending from the upper half of the posterior margin of the eye to the middle caudal-fin rays, absence of a humeral blotch, 16–19 branched anal-fin rays, 2–4 maxillary teeth, six branched pelvic-fin rays, and the absence of dark pigmentation crossing the eye. Hyphessobrycon cyanotaenia, a species described from few specimens from the aquarium trade without precise locality, is redescribed herein based on extensive material, and its known distribution is discussed and rectified from the original description.

Diet and ecomorphology of Leporinus reticulatus (Characiformes: Anostomidae) from the upper Rio Juruena, MT, Brazil: ontogenetic shifts related to the feeding ecology

The conservation of diverse and well-distributed fish taxa, as the genus Leporinus, relies intrinsically on the knowledge of the ecological attributes of its representatives. Aiming to increase this knowledge, studies on diet and ecomorphology are ideal to provide important information about species ecology. Thus, this study aimed to analyze aspects of feeding ecology of L. reticulatus, from the upper Rio Juruena, Mato Grosso State, Brazil. The diet of specimens in different ontogenetic stages was compared, as well as their teeth morphology and ecomorphological attributes. Leporinus reticulatus presented omnivorous diet, with higher consumption of invertebrates by smaller specimens (younger ones), and gradual introduction of plant items in larger specimens (older ones). The items consumed by the individuals and the ecomorphological attributes indicated that the species is generalist and opportunistic, besides its association with the river bottom, evidencing a benthic feeding behavior. This species presents a gradual ontogenetic modification in teeth shape and mouth positioning, ranging from a terminal mouth with tricuspid teeth, in smaller specimens, to an inferior mouth with spatula shaped teeth with no cusps, in larger specimens.The ecomorphological attributes indicate an increasing swimming efficiency, and ability for performing vertical displacements, along the ontogenetic development, which in addition to the morphological ontogenetic alterations in the buccal apparatus, contributes to a better ability to explore another niches.