Color pattern is an important character in the systematics and alpha-taxonomy of electric fishes of the genus Gymnotus. This paper presents evidence of color variation in populations of G. pantanal found in the streams Jacutinga and Pinheirinho, in the upper Paraná River basin, southern Brazil. Color variations were corroborated for morphological and cytogenetic data. Our results show the importance of integrating morphologic and cytogenetic data in the taxonomy of the Gymnotus species.
Gymnotidae; Gymnotus pantherinus species-group; La Plata River basin; Karyotype
