Saturday, August 5, 2017

[Ichthyology • 2017] Hyphessobrycon pinnistriatus • A New species of Hyphessobrycon (Ostariophysi, Characiformes) from the Rio Teles Pires, Rio Tapajós basin, Brazil


Hyphessobrycon pinnistriatus 
Carvalho, Cabeceira & Carvalho, 2017

 DOI: 10.1111/jfb.13362  

Abstract

A new species of Hyphessobrycon from the upper Rio Tapajós basin, in the Tapajós–Juruena ecoregion, is described. Hyphessobrycon pinnistriatus n. sp. is distinguished from its congeners by having a black, oblique stripe extending from the origin of the second branched ray to the distal end of the third branched anal-fin ray, lacking a conspicuous black midlateral stripe on the body, inner premaxillary teeth with up to seven cusps, and fins normally hyaline or with scattered chromatophores. The description of a new species that is restricted to the Tapajós–Juruena ecoregion is consistent with this region being an area of high endemism of freshwater fishes.


Figure 4.  Hyphessobrycon pinnistriatus, live specimen (same locality as holotype), not preserved (c. 26·0 mm standard length).

Hyphessobrycon pinnistriatus new species
Hyphessobrycon sp. 1 (Buckup et al., 2011: 243; list of species).
 Hyphessobrycon sp. n. (Battirola et al., 2015: 477 citation); Cabeceira et al. (2015: 199, 204; list of species and photo).

Diagnosis: Hyphessobrycon pinnistriatus differs from all congeners by having a black, oblique stripe that is largely parallels and covers the second and third anal-fin rays (Fig. 1), extending from the origin of the second branched ray to the distal end of the third branched anal-fin ray (v. anal fin hyaline, with uniformly distributed chromatophores, or margin blackish in all other species of Hyphessobrycon). Additionally, the new species can be distinguished from other congeners by lacking a conspicuous black midlateral stripe on the body, inner premaxillary teeth with up to seven cusps and from Hemigrammus unilineatus (Gill 1858), a non-congener but similar species, by having 20–23 branched anal-fin rays (v. 24–25), maxilla with two or three tetra to heptacuspidad maxillary teeth (v. three to seven tricuspidad maxillary teeth) and caudal fin lacking scales (v. caudal-fin lobes scaled).

Etymology: The species name is a combination of the Latin pinna, meaning fin and striatus, meaning stripe and is in reference to the black stripe on its anal fin. An adjective in apposition.

Ecological notes: The type locality of Hyphessobrycon pinnistriatus is a second order stream (sensu Strahler, 1957), known as an igarapé, surrounded by secondary forest in regeneration. The bottom of the stream is mainly composed of silt, with litter on the margins and few branches and trunks of a diameter greater than 10 cm. In the pools, there is flocculant sediment that is easily disturbed from submerged litter and macrophytes were found at sites with a little more water flow (Fig. 6). Most individuals of H. pinnistriatus were only observed in more lentic environments, swimming in small schools of five to 20 individuals. Individuals were also observed swimming alone and together with other species of Characidae, such as Moenkhausia phaeonota Fink 1979 and Hyphessobrycon heliacus Moreira, Landim & Costa 2002 near igarapé margins with depth ranging from 20 to 40 cm. Individuals were sometimes also observed foraging among the submerged litter in the igarapé margins (F. G. Cabeceira, pers. obs.). This species has also been found in habitats with faster water, no vegetation and substrata consisting of sand and mud.

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F. R. Carvalho, F. G. Cabeceira and L. N. Carvalho. 2017. New species of Hyphessobrycon from the Rio Teles Pires, Rio Tapajós basin, Brazil (Ostariophysi, Characiformes).  
 Journal of Fish Biology. DOI: 10.1111/jfb.13362 

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