Abstract
ABSTRACT A new species of Moenkhausia is described from the rio Arinos drainage, rio Tapajós basin, Mato Grosso, Brazil. The new species is diagnosed from all congeners, except M . hemigrammoides , M . nigromarginata , and Moenkhausia rubra by having intense diffuse dark pigmentation on the dorsal and anal fin-rays. The new species can be distinguished from the above mentioned species by the combination of 20-23 branched anal-fin rays, presence of a vertically elongate roughly rectangular humeral spot surpassing the lateral line ventrally, absence of a well-defined black spot on the distal portion of the dorsal fin and lack of a series of longitudinal dark zigzag stripes on body. The new species is herein described along with a report and discussion of a possible connection between the rio Tapajós and rio Paraguay basins, near Diamantino Municipality, Mato Grosso.
Highlights
Moenkhausia Eigenmann currently includes about 80 valid species (Eschmeyer, 2016) widely distributed in South American freshwaters
Species of the “Moenkhausia oligolepis/M. sanctaefilomenaespecies complex” (Costa, 1994; Lima & Toledo-Piza, 2001; Lima et al, 2007; Benine et al, 2009) have a characteristic reticulated color pattern on body, red eye and a light area followed by a large dark caudal-peduncle blotch, Moenkhausia browni Eigenmann, M. comma Eigenmann, and M. levidorsa Benine are relatively large species with deep body, M. ceros Eigenmann, M. collettii Steindachner and M. lopesi Britski & de Silimon are small and shallow-bodied forms as well as Moenkhausia bonita Benine, Castro & Sabino and M. hemigrammoides Géry, which are Hemigrammus-like species very similar to H. marginatus Ellis and H. unilineatus Gill, respectively, and M. agnesae Géry and Moenkhausia cosmops Lima, Britski & Machado, with colorful bodies, appreciated as ornamental species
A notable condition present in Moenkhausia mutum is the concentration of dark chromatophores at the distal portions of pelvic, dorsal, and anal fins
Summary
Moenkhausia Eigenmann currently includes about 80 valid species (Eschmeyer, 2016) widely distributed in South American freshwaters It is a Characidae genus defined by a combination of the presence of teeth arranged in two rows in the premaxilla, with five teeth in the inner row, lateral line complete, and small scales partially covering the caudal-fin lobes (Eigenmann, 1903, 1917). None of these characters are unique for the genus and all are known to be highly homoplastic within the Characidae (Mirande, 2010). Species of the “Moenkhausia oligolepis/M. sanctaefilomenaespecies complex” (Costa, 1994; Lima & Toledo-Piza, 2001; Lima et al, 2007; Benine et al, 2009) have a characteristic reticulated color pattern on body, red eye and a light area followed by a large dark caudal-peduncle blotch, Moenkhausia browni Eigenmann, M. comma Eigenmann, and M. levidorsa Benine are relatively large species with deep body, M. ceros Eigenmann, M. collettii Steindachner and M. lopesi Britski & de Silimon are small and shallow-bodied forms as well as Moenkhausia bonita Benine, Castro & Sabino and M. hemigrammoides Géry, which are Hemigrammus-like species very similar to H. marginatus Ellis and H. unilineatus Gill, respectively, and M. agnesae Géry and Moenkhausia cosmops Lima, Britski & Machado, with colorful bodies, appreciated as ornamental species
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