Map showing the localities of species Gymnotus with known cytogenetic formulas. Data are taken from a review of the cytogenetic literature by Milhomem et al. (2007), from Margarido et al. (2007) and Lacerda & Maistro (2007), and from the species discussed in this paper. See Table 4 for chromosome numbers of these species, and further locality information. At some localities the coordinates are approximate because detailed information was not available from the respective papers.