New species of Moenkhausia Eigenmann (Characiformes: Characidae) from Rio Xingu and Rio Tapajós basins, Brazil, with comments on a putative case of polymorphic Batesian mimicry

A new Moenkhausia (Characiformes: Characidae) from rio Brao Norte, rio Tapajs basin, with comments on the fish endemism of Serra do Cachimbo plateau

A new species of Moenkhausia is described from the rio Brao Norte, a tributary of Rio Teles Pires draining the Serra do Cachimbo, rio Tapajs basin, Par, Brazil. The new species is diagnosed from all congeners, except M. moisae and M. pirauba, by having a high number of scales in the longitudinal series (4346 vs. 2341 in other Moenkhausia species). It can also be distinguished from the aforementioned species based on the combination of the following characters: a single humeral blotch, 2125 branched anal-fin rays, and a round and symmetrical caudal blotch not continuous anteriorly with the dark midlateral stripe. The new tetra herein described represents an additional, possibly endemic, taxon from the headwaters draining from Serra do Cachimbo, in the Brazilian Shield.

Stream ichthyofauna of the Tapajós National Forest, Pará, Brazil

The fish fauna of freshwater streams in the Tapajos National Forest was surveyed and a list of species is presented. The sampling was conducted from 2012 to 2013 during the dry season. Fish were collected with dip nets and seine nets in 22 streams of 1(st) to 3(rd) order. Sampling resulted in 3035 specimens belonging to 117 species, 27 families and six orders. The most abundant species were Bryconops aff. melanurus, Hemigrammus belottii, and Hemigrammus analis. Four undescribed species were recognized, one of which is known only from the area of this study. A significant dissimilarity was observed in fish species composition among drainage systems. This is the first survey of the stream ichthyofauna in the Tapajós National Forest, and it presents relevant information for future studies and decision-making in the management and conservation of fish fauna in this conservation unit.

Ichthyofauna of the upper Juruena river on Chapada dos Parecis, Mato Grosso, Brazil

Abstract The fishes herein included were collected in four small streams of the upper rio Tapajós basin. Through fieldwork carried out in 2011, 2013 and 2014 during the low water season 1.728 specimens belonging to 22 species distributed in 11 families, and five orders were captured. Characidae was the most representative family both in number of species and specimens captured. The most abundant species were Hyphessobrycon melanostichos, H. hexastichos, and H. notidanos. Five species are recognized as new, and four as endemic to the upper rio Tapajós basin. This study represents the first fish inventory for the region and will provide valuable information for the conservation of the poorly known diversity of fishes of the Chapada dos Parecis, in the headwaters of the upper rio Tapajós basin.

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.

Redescription of Astyanax multidensEigenmann, 1908 (Characiformes: Characidae), a small characid of the Brazilian Amazon

Astyanax multidensis redescribed based on syntypes and additional specimens from the rio Amazonas at Silves, Amazonas State and Óbidos, Pará State, and the rios Trombetas, Tapajós, Xingú, and Araguaia.Astyanax multidensis distinguished from congeners by the unique combination of five to seven maxillary teeth, 31 to 34 pored lateral-line scales, 20 to 23 branched anal-fin rays, and a dark triangular blotch restricted to the middle caudal-fin rays. Astyanax multidens was collected syntopically with Jupiaba paranatinga in the rio Tapajós basin and with Jupiabacf. essequibensis in the rio Xingu basin, which have paired anteriorly oriented pelvic-fin spines, a antipredatory mechanism. Based on the external morphological similarity betweenAstyanax multidens and the two species ofJupiaba, their sympatric occurrence, and their distinct phylogenetic position, we interpret this a case of Batesian mimicry.

Centromochlus meridionalis, a new catfish species from the southern Amazonian limits, Mato Grosso State, Brazil (Siluriformes: Auchenipteridae)

Centromochlus actually comprises eleven species, being the most problematic genus among the Centromochlinae, including morphologically heterogeneous taxa. The Centromochlus species have a wide distributional area on northern South America. Centromochlus meridionalis, new species, is described from headwaters of rio Teles Pires, contributor of rio Tapajós, Mato Grosso State, Brazil, and represents one of the southernmost records of a centromochlin catfish for Meridional Amazon rivers. Centromochlus meridionalis is promptly distinguished from its congeners by the small orbital diameter (relative to head length), and also by the combination of absence of first nuchal plate, anterior margin of dorsal-fin spine smooth, six branched rays in anal fin, seven pairs of ribs and 34 vertebrae. They are small sized catfishes with adults between 33 to 61 mm in standard length. The modified male anal fin is conspicuous, with the third unbranched ray enlarged, about twice the width of first unbranched ray. The new species inhabits a region strongly endangered by environmental changes due to expansion of agropecuary activities on Brazilian Amazon, which include this species in an uncertain situation regarding the conservation status of its natural population.