Two new species of Hemibrycon tetras have been described in a review of the species found east of the Andes in the most recent issue of the journal Neotropical Ichthyology.
Vinicius Bertaco and Luiz Malabarba recognise nine species in their study, of which two species from Peru: Hemibrycon inambari from the upper Madre de Dios river drainage and H. mikrostiktos from the Ucayali River drainage are described as new species.
Hemibrycon mikrostiktos (pictured top) differs from congeners in having a small humeral spot covering only 2–3 scale rows, 40–42 lateral-line scales, 3–4 scale rows below the lateral line, seven pelvic-fin rays, and 18–21 branched anal-fin rays.
This species is named after the small humeral spot (Greek mikros=small and stiktos=spot).
Hemibrycon inambari (above) is distinguished from congeners in having 41–44 lateral line scales, 13–16 predorsal scales, 6–10 scales along the anal-fin base, 17–18 rakers on the first gill arch, 41–43 vertebrae, 5–7 cusps on the inner teeth of the upper jaw, five cusps on the front three lower-jaw teeth, the absence of bony hooks in the caudal-fin rays of males, seven pelvic-fin rays, the absence of a wide black asymmetrical spot on the base of the caudal fin, and humeral spot covering 7–8 scale rows.
This species is named after its type locality (the Inambari River).
The other seven species regarded as valid in the study are: H. beni from the Beni River drainage, Bolivia; H. helleri from the upper Ucayali River drainage, Peru; H. huambonicus from the Huallaga and Marañon river drainages, Peru; H. jeslkii from the upper Marañon, Ucayali and Madeira river drainages, Bolivia, Brazil, and Peru; H. metae from the Orinoco River drainage, Colombia and Venezuela, and the Caribbean coastal drainages of Venezuela; H. polyodon from the Pastaza River drainage, Ecuador; H. surinamensis from the coastal drainages of French Guiana and Suriname, and from the lower Tapajós, Tocantins and Xingu river drainages, Brazil; H. taeniurus from the river drainages on Trinidad Island, Trinidad and Tobago, and H. tridens from the upper Ucayali River drainage, Peru.
For more information, see the paper: Bertaco, VA and LR Malabarba (2010) A review of the Cis-Andean species of Hemibrycon Günther (Teleostei: Characiformes: Characidae: Stevardiinae), with description of two new species. Neotropical Ichthyology 8, pp. 737–770.