A new Gymnotus (Teleostei: Gymnotiformes: Gymnotidae) from the Pantanal Matogrossense of Brazil and adjacent drainages: continued documentation of a cryptic fauna

Abstract

Here we describe a new species of Gymnotus, G. pantanal n. sp., from the Pantanal Matogrossense of Brazil, using morphological, cytogenetic, and molecular data. Specimens ascribed to the new species are also known from areas downstream in Paraguay, and from the adjacent Guaporé basin of Bolivia. The new species most closely resembles G. anguillaris in possessing an elongate body, slender profile, long body cavity, and shorter head than other congeners. The new species also resembles G. anguillaris in the presence of pale narrow bands restricted to the area below the lateral line on the anterior half of the body. The new taxon differs from G. anguillaris in possessing more narrowly set eyes, a wider and deeper head, a larger branchial opening, longer pectoral fins with more fin rays, and fewer pored posterior lateral-line scales. The new species inhabits rooted grasses and floating macrophytes in small creeks and along the banks of larger blackwater rivers. Populations are found syntoptically with G. inaequilabiatus and G. sylvius. Compared with these species, the new species exhibits a distinct combination of microsatellite DNA amplification patterns, and chromosomal and external features. These results confirm earlier studies showing the power of a multidisciplinary approach to characterizing the enormous and often cryptic diversity of Neotropical fishes.

A massive invasion of fish species after eliminating a natural barrier in the upper rio Paraná basin

“…The only gymnotid genus recorded in the upper rio Paraná basin is Gymnotus, monophyletic and the most diverse and widespread of South American electric fishes (Fernandes et al, 2005), with a single species previously found in this basin: G. carapo. Electrobiological, cytogenetic and molecular studies have shown that Gymnotus currently encompasses numerous different species throughout the Neotropical region, some of which are still undescribed (Campos-da-Paz, 2003).…”

A new species of Gymnotus (Gymnotiformes: Gymnotidae) from the Fitzcarrald Arch of southeastern Peru

“…Materials examined are listed in Campos-da-Paz & Costa (1996), Albert (2001), Albert & Crampton (2001, Campos-da-Paz (2002), Crampton et al (2003, Maldonado-Ocampo & Albert (2003), Fernandes et al (2005), Cognato et al (2007), and Richer-deForges et al (2009 …”

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

“…Counts and measurements followed Albert (2001) and Fernandes et al (2005). When referring to Gymnotus pantanal sensu stricto or typical color pattern we followed Fernandes et al (2005), who found a color pattern of obliquely-oriented thin pale pigment bands.…”

“…Gymnotus pantanal was described by Fernandes et al (2005) in the Paraná-Paraguay system, in Brazil and Paraguay, and in the River Chapare-Mamoré, in Bolivia. Fernandes et al (2005) used morphological, cytogenetic, and molecular data to describe that species; in their diagnosis color pattern was the main morphological trait: 'Gymnotus pantanal differs from other members of the G. pantherinus Steindachner speciesgroup (except G. anguillaris Hoedeman) in possessing a color pattern composed of thin obliquely-oriented pale pigment bands (about one third the width of the dark bands) with wavy margins restricted to the ventral portion of the body (rarely extending above the lateral line) on the anterior half of the body'. Later, Graça & Pavanelli (2007) and Margarido et al (2007) reported this species for the upper Paraná River basin.…”

“…Despite the high diversity of this genus, only eight species of Gymnotus have been cytogenetically analyzed: G. paraguensis Albert & Crampton, 2003, G. pantherinus (Steindachner, 1908, G. inaequilabiatus (Valenciennes, 1839) G. sylvius Albert & Fernandes-Matioli, 1999(FernandesMatioli et al, 1998), G. pantanal Fernandes, Albert, DanielSilva, Lopes, Crampton & Almeida-Toledo, 2005(Fernandes et al, 2005Silva & Margarido, 2005), G. mamiraua Albert & Crampton, 2001(Milhomem et al, 2007, Gymnotus sp. (Lacerda & Maistro, 2007) and G. cf.…”