Evidence of the color pattern variation in populations of Gymnotus pantanal (Gymnotiformes) from three streams in the upper Paraná River basin, Brazil

Abstract

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.O padrão de colorido é um caráter muito importante na sistemática e alfa taxonomia de espécies do gênero Gymnotus. O objetivo deste trabalho foi apresentar evidências de variação no padrão de colorido em populações locais de Gymnotus pantanal encontrados nos córregos Jacutinga e Pinheirinho, bacia do alto rio Paraná, sul do Brasil. A variação no padrão de colorido foi corroborada por dados morfológicos e citogenéticos. Nossos resultados demonstram a importância da integração de dados morfológicos e citogenéticos na taxonomia de espécies de Gymnotus.

Gymnotus paraguensis, a Good Example of Phenotypic Plasticity in the Pantanal Biome, Brazil

“…However, considerable variation in the coloration pattern of G. pantanal has already been observed in local populations from the Jacutinga and Pinheirinho streams, located in the upper Paraná River basin. 55 G. paraguensis in the upper Paraguay River basin presents a wide polymorphism in the color pattern as mentioned above, with large numbers of oblique, alternating lighter and darker bands along the entire length of the body.…”

“…It would nevertheless appear to be most parsimonious to believe that these karyotypically diverse units represent distinct species, and that the variation in coloration patterns observed in G. paraguensis reflects the phenotypic plasticity of this species, a common phenomenon in fish. 55,72,73 What is clear is that the subspecies proposed by Craig et al 29 are not supported by the data, and Fricke et al, 8 for example, do not apply the subspecies category to G. carapo in their catalog of fishes (www.researcharchive.calacademy.org/research/ ichthyology/catalog/fishcatmain.asp).…”

“…Gymnotus pantanal. Twenty-one to twenty-five bands, obliquely oriented, with wavy irregular margins on ventrolateral surface, extending from tip of tail to pectoral-fin base; head not banded, spotted, or blotched; variable color pattern in subadults and adults were identified 55 ; straight body shape in the profile dorsal; overall body subcylindrical; anal fin with 180-233 rays (mode = 222, n = 13); karyotype 2n = 39 (15m-sm +24st-a) for male and 2n = 40 (14m-sm +26st-a) for female chromosomes. The range of analyzed specimens was 160-250 mm TL, mean 190.6 -27.6 mm TL.…”