New species of Gymnotus (Gymnotiformes, Teleostei) from southeastern Brazil: Toward the deconstruction of Gymnotus carapo

A new species of Gymnotus is described from Atlantic and Rio Parana drainag es of Sao Paulo State, Brazil. The new species inhabits small creeks with m urky, slowly moving water, and grows to about 300 mm in length. The new spe cies is diagnosed by the presence of 21 or 22 pairs of obliquely oriented d ark pigment bands with wavy margins in which the dark bands are more narrow than the white interband regions. The new species also differs from other members of Gymnotus in features of body proportion, electric organ discharg e (EOD), karyotype, and microsatellite DNA. The color pattern of the new sp ecies most closely resembles the sympatric G. inaequilabiatus. Together, th ese two species share three features with G. carapo, the type species of th e genus: a relatively deep body, wavy margins of the pigment bands, and a c lear patch at the caudal end of the anal fin. Based on these three characte rs specimens collected from as far apart as Argentina and Colombia have bee n referred to the nominal species "G. carapo," despite sizable variation in color pattern and body proportions. A result of this coarse taxonomy is th at "G. carapo" is thought to have the most extensive geographical range of any gymnotiform species. Identifying the new species from within this range documents a previously overlooked component of diversity in the group. The data also demonstrate that genetic differences accompany morphological var iation in a widespread assemblage of Neotropical fishes.