Rio Juruena Research Articles

A new species of Moenkhausia Eigenmann (Characiformes: Characidae)from the upper rio Juruena basin, Central Brazil.

Moenkhausia lineomaculata, new species, is described herein from the upper rio Juruena, upper rio Tapajós basin. The new species seems to be part of a monophyletic group formed by M. cosmops, M. cotinho, M. diktyota, M. forestii, M. oligolepis, M. sanctaefilomenae, and M. pyrophthalma, the Moenkhausia oligolepis/M. sanctaefilomenae complex, by sharing a reticulated color pattern on body and the presence of a light area preceding a wide, dark caudal-peduncle blotch. The new species is distinguished from these species, except M. cotinho, by the presence of longitudinal series of dark dots on body, and from M. cotinho by the humeral blotch evenly pigmented along its length and by having the dark line along horizontal septum starting approximately at the vertical through dorsal-fin origin. The new species presents intraspecific variation in lateral-line scales perforation, a feature often present in species of the aforementioned group.

Moenkhausia rubra, a new species from rio Juruena, upper rio Tapajós basin, Brazil (Characiformes: Characidae)

Moenkhausia rubra, new species, is described from the upper rio Juruena, rio Tapajós basin, Mato Grosso, Brazil. The new species is distinguished from its congeners, except M. hemigrammoidesand M. nigromarginata, by the dark pigmentation on the anteriormost rays of both dorsal and anal fins. Moenkhausia rubrais distinguished from the aforementioned species by the number of branched anal-fin rays 17-20 (vs. 20-25), presence of a dark blotch on the caudal peduncle extending to middle caudal-fin rays, absence of longitudinal black zigzag stripes between longitudinal rows of scales on body, and other details of coloration.

A new species of Utiaritichthys Miranda Ribeiro (Characiformes: Serrasalmidae) from the Serra dos Parecis, Tapajós drainage

Utiaritichthysesguiceroi is described from the upper portion of the rio Juruena, rio Tapajós drainage, Mato Grosso State, Central Brazil. The new species distinguished from its two congeners, U. sennaebragai Miranda Ribeiro and U. longidorsalis Jégu, Tito de Morais & Santos, by having 99 to 101 perforated scales on lateral line (vs. 69 to 83), presence of 17 to19 prepelvic spines (vs. 9-13 in U. sennaebragai and 28-31 in U. longidorsalis), 20 to 21 postpelvic spines (vs. 15 to 19 in U. sennaebragai, and 14 in U. longidorsalis), and 23 to 25 circumpeduncular scales (vs. 30-48 in U. sennaebragai, and 33-35 in U. longidorsalis). Furthermore, the new species differs from U. longidorsalis by having larger interdorsal width, and adipose-fin base length (11.8-15.6 vs. 7.1-7.9% of SL, and 4.2-5.8 vs. 3.7-3.8% of SL, respectively).

New species of Creagrutus Günther (Characiformes: Characidae) from rio Tapajós basin, Brazil, with comments on its phylogenetic position.

Creagrutus nigrotaeniatus n. sp. is described from the rio Juruena basin, upper rio Tapajós system, Mato Grosso State, Brazil. Creagrutus nigrotaeniatus differs from its congeners by having the dentigerous surface of the premaxilla longitudinally elongate from ventral view, 4-5 post-anal scales and 2-4 maxillary teeth. The new species also has the anterior margin of hyomandibula straight or slightly concave which is a unique condition within the genus, and possesses a series of non-exclusive osteological modifications (e.g. medial opening of the dentary foramen located distinctly anteroventral to the tip of Meckel's cartilage; anterior portion of the laterosensory canal segment in first infraorbital terminating distinctly posterior to the anterior margin of this bone; presence of the third posttemporal fossa within the epioccipital; one epural present). A comparison with Caiapobrycon tucurui is provided and the placement of the new species within Creagrutus and its close relationship with C. cracentis, C. gephyrus, and C. maxillaris are discussed.

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

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.

Two new Amazonian species of armored catfishes (Siluriformes: Loricariidae): Ancistrus verecundus and Ancistrus parecis

Two new species Ancistrus are described: A. verecundus from the upper rio Madeira basin and A. parecis from the upper rio Juruena, rio Tapajós basin, Brazil. The two species differ from all congeners except A. jataiensis, A. reisi, and A. tombador in the absence of an adipose fin which is replaced by a series of median platelets forming a low postdorsal ridge. Ancistrus verecundus is further distinguished from these species, except A. tombador by the broad naked margin of the snout and reduced tentacle development. Ancistrus verecundus differs from A. tombador in various morphometric features, and in having the base of the first anal-fin pterygiophore covered by skin (vs. base of the first anal-fin pterygiophore exposed and forming a platelet-like element). Ancistrus verecundus and A. tombador have two or more dermal plates of the dorsal plate series between the end of the postdorsal ridge and the origin of the first plate-like procurrent caudal-fin ray, whereas the other species of the genus that lack an adipose fin, including A. parecis, have one or none. Ancistrus parecis is further distinguished from A. tombador and A. verecundus by the presence of tentacles in adults. It also differs from A. tombador in morphometric and meristic features and from A. jataiensis and A. reisi in the length of the mandibular tooth row, the number of teeth on dentary and premaxillary, and the caudal-peduncle depth. A key is provided for the identification of species of Ancistrus lacking an adipose fin.

A NEW SPECIES OF NEUSTICOMYS (ICHTHYOMYINI, SIGMODONTINAE) FROM CENTRAL BRAZILIAN AMAZONIA

The known species of genus Neusticomys occur from the Colombian and Ecuadorian Andes southward to the Amazonian lowlands of Peru and eastward to Venezuela, Guyana, French Guiana, and Amapa, Brazil. In this study we describe a new species, Neusticomys sp. nov., from the Rio Juruena on the Central Brazilian shield, extending the distributional range of the genus and placing it in the center of South America. Neusticomys sp. nov. is defined and diagnosed by a unique combination of character states: ears and feet covered by dark brown hairs; size small; inferior zygomatic root anterior to 1st upper molar; orbicular apophysis absent; M3 present; m3 frequently present; posteroloph absent on M2 and M3; reduction of posterior lobe relative to the anterior lobe on M2; and 2n = 92, FN = 98.