Abstract
Two new species of Astyanax are described from eastern Brazil: A . microschemos from the córrego Palmital, rio Itapemirim drainage, Espírito Santo, and A . pelecus from the rio Pardo drainage, Bahia. Astyanax microschemos differs from its congeners by its shallower body depth, 26.9-29.7% of standard length, the presence of one vertically elongate humeral spot that extend above and below the lateral line, smaller interorbital width, 26.9-30.4% of head length, and the possession of 14-18 branched anal-fin rays. Astyanax pelecus differs from its congeners in the possession of only one humeral spot limited to the region dorsal to the lateral line, conspicuous, dark, midlateral body stripe extending from the upper margin of the opercle to the caudal-fin base, a shallower body depth, 26.7-34.8% of standard length, and the possession of 16-18 branched anal-fin rays, 38-39 scales in the lateral-line series, and four scales between the lateral line and the pelvic-fin origin. Astyanax microschemos has a massive head, short snout, usually smaller than the orbital diameter, shallow body depth, and vertically-elongate humeral spot that serve to include it in the A . scabripinnis species complex. A comparative synopsis of this complex is provided.
Highlights
Astyanax Baird & Girard, 1854 is a speciose genus of Neotropical characid fishes, comprising about 86 valid described species (Lima et al, 2003) and occurring in diverse habitats within freshwater drainages from southern United States to central Argentina
In order to focus the discussion of the species diversity to a limited number of similar species, we utilize the following combination of characters that include those of Eigenmann (1921:273) as diagnosing A. scabripinnis, to delimit the A. scabripinnis species complex: body deepest and heaviest in area proximate to middle of pectoral fins, head heavy, snout short and abrupt by tapering, body depth smaller than 41% of standard length (SL), reduced number of branched anal-fin rays (13-21, usually 17-18, rarely 22 or 23), presence of one or two humeral spots, and a dark, midlateral, body stripe extending to the tip of the middle caudal-fin rays
A. pelecus differs from other members of the genus in its distinctive color pattern: it possesses only one humeral spot limited to the region above lateral line series, and has a conspicuous midlateral body stripe extending from the upper margin of the opercle to the caudal-fin base, a putative autapomorphy of this species
Summary
Astyanax Baird & Girard, 1854 is a speciose genus of Neotropical characid fishes, comprising about 86 valid described species (Lima et al, 2003) and occurring in diverse habitats within freshwater drainages from southern United States to central Argentina. The examination of Astyanax samples reveals two undescribed species from the rio Pardo and rio Itapemirim, coastal drainages of Bahia and Espírito Santo states, respectively, which are described. This region possesses an endemic ichthyofauna that is presently suffering large anthropogenic impacts. In order to focus the discussion of the species diversity to a limited number of similar species, we utilize the following combination of characters that include those of Eigenmann (1921:273) as diagnosing A. scabripinnis, to delimit the A. scabripinnis species complex: body deepest and heaviest in area proximate to middle of pectoral fins, head heavy, snout short and abrupt by tapering, body depth smaller than 41% of SL (mean 30-33% of SL), reduced number of branched anal-fin rays (13-21, usually 17-18, rarely 22 or 23), presence of one or two humeral spots, and a dark, midlateral, body stripe extending to the tip of the middle caudal-fin rays
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