Journal of Fish Biology (2017) doi:10.1111/jfb.13405, available online at wileyonlinelibrary.com A new species of Astyanax (Characiformes: Characidae) from Dolina Água Milagrosa, Rio Paraguai basin, Mato Grosso, Brazil W. J. da Graça*†, C. A. M. Oliveira‡, F. C. T. Lima§, H. P. da Silva‖ and I. M. Fernandes¶ *Universidade Estadual de Maringá, Departamento de Biologia e Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Av. Colombo, 5790, Bloco G-80, Sala 7, 87030-230, Maringá, Paraná, Brazil, ‡Universidade Estadual de Maringá, Departamento de Biologia, Programa de Pós Graduação em Ecologia de Ambientes Aquáticos Continentais e Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Av. Colombo, 5790, Bloco G-80, Sala 5, 87030-230, Maringá, Paraná, Brazil, §Universidade Estadual de Campinas, Instituto de Biologia, Museu de História Natural Prof. Adão José Cardoso, Rua Albert Einstein, s/n, Barão Geraldo, 13083-863, Campinas, São Paulo, Brazil, ‖Universidade Estadual de Maringá, Programa de Pós Graduação em Biologia Comparada, Av. Colombo, 5790, Bloco G-80, Sala 5, 87030-230, Maringá, Paraná, Brazil and ¶Universidade Federal de Rondônia, Campus Universitário de Rolim de Moura, Av. Norte Sul, 730, Morada Nova, 78060-900, Rolim de Moura, Rondônia, Brazil urn:lsid:zoobank.org:pub:D90C4200-85AB-4E73-AA3E-7B70A00D0DA9 (Received 24 June 2016, Accepted 31 July 2017) A new species of Astyanax is described from the upper Rio Paraguai basin, Mato Grosso State, Brazil. The new species can be distinguished from congeners by having the body intensely yellowish in life (v. silvery, reddish or lightly yellow) and by morphometric and meristics traits. Astyanax dolinae n. sp. cannot be assigned to any of the Astyanax species complex currently recognized for the genus. It is only known from the Dolina Água Milagrosa, a karstic sinkhole lake, entirely fed by groundwater, surrounded by Cerrado, the savannah-like vegetation of central South America. © 2017 The Fisheries Society of the British Isles Key words: endemism; karstic sinkhole; Neotropical region; Río de La Plata; taxonomy. INTRODUCTION Astyanax Baird & Girard 1854 is the second most species-rich genus of Characidae, currently comprising 148 valid species (Eschmeyer et al., 2017). Astyanax is widely distributed throughout the southern United States (Page & Burr, 2011) to the Río Colorado–Río Negro basins in northern Patagonia, Argentina (Casciotta et al., 2005). The revision of Astyanax by Eigenmann (1921, 1927) remains the only complete taxonomic appraisal of the genus. As remarked by Weitzman & Fink (1983) and †Author to whom correspondence should be addressed. Tel.:+ 55 4430115309; email: weferson@nupelia.uem.br 1 © 2017 The Fisheries Society of the British Isles