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

Abstract

Herein Gymnotus chaviro is described from the Alto Yuruá (upper rio Juruá) of southeastern Peru, where it is locally abundant in terra firme streams and floodplain oxbow lakes, and occurs sympatrically and syntopically with the type species of the genus G. carapo. The new species is diagnosed by a unique combination of morphometric, meristic, and osteological traits, and a characteristic color pattern in which the dark band-pairs are unbranched and incompletely separated, and the pale inter-bands rarely reach to the dorsal mid-line on the anterior half of the body, being crescent-shaped in abdominal area. Gymnotus chaviro is a member of the G. carapo species group, with which it shares the presence of two pores in the dorsolateral portion of the preopercle, dark pigment bands with wavy margins that become broken and/or loose contrast with the ground color through growth, a clear patch at the caudal end of an otherwise darkly pigmented anal fin, and more than four arrowhead-shaped (anteroposteriorly compressed) teeth in the anterior portion of the dentary. Gymnotus chaviro is most similar in external appearance to G. curupira of lowland Western Amazonia in possessing a slender lateral profile (mean body depth less than 9% total length), a similar color pattern (median number of bands 19 with bands less distinct on dorsum), a large inter-orbital distance (mean greater than 41% head length), a broad head (mean head width greater than 65% head length) and a large mouth (mean mouth width greater than 43% head length). This new species can also be distinguished from G. curupira by the configuration of the preopercular pores, and by several meristic traits of squamation and fin rays. This is the first gymnotiform species described from the interior of the Fitzcarrald Arch, and the only gymnotiform species known to date that is endemic to this upland region of the western Amazon.En el presente trabajo se describe Gymnotus chaviro de Alto Yuruá (parte alta del Río Juruá) en el sureste de Peru. Esta especie es abundante en arroyos de tierra firme y llanuras con lagos en herradura, ocurre de manera sintópica y simpátrica con la especie tipo del genero, G. carapo. La nueva especie se diagnostica por una combinación única de rasgos morfométricos, merísticos y osteológicos, así como un patrón característico de bandas pares obscuras no ramificadas e incompletamente separadas, alternando con bandas claras que raramente alcanzan el centro de la línea dorsal en la mitad anterior del cuerpo adquiriendo forma de media luna en la parte abdominal. Gymnotus chaviro es un miembro del grupo de especies de G.carapo, con quien comparte la presencia de dos poros en la porción dorso lateral del preopérculo, bandas con pigmentos obscuros con márgenes ondulados que se parten y/o pierden el contraste con el color de fondo a medida que crece, aleta anal obscura con un claro parche de un pigmento obscuro en borde caudal y más de cuatro dientes en forma de punta de flecha (anteroposteriormente comprimidos) en la porción anterior del dentario. Gym...

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

“…Females had 7 meta-submetacentric chromosome pairs and 13 acrocentric chromosome pairs; males had 7 metasubmetacentric chromosome pairs plus a large metacentric chromosome (chromosome Y), and 11 acrocentric chromosome pairs plus two non-homologous medium sized acrocentric chromosomes (chromosomes X Maxime & Albert, 2009;Richer-de-Forges et al, 2009). Therefore, we thought at first that the atypical color pattern might suggest the existence of a new species.…”

“…The genus Gymnotus Linnaeus comprises 35 valid species of electric fishes, including aggressive and nocturnal gymnotiform eels of shallow freshwaters distributed from southern Mexico to Argentina (Cognato et al, 2007;Maxime & Albert, 2009;Richer-de-Forges et al, 2009). 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.…”

A New Species of Gymnotus (Gymnotiformes: Gymnotidae) from Rio Tiquié in Northern Brazil

“…G YMNOTUS is the most species-rich genus of Neotropical electric fishes (Gymnotiformes), with 35 species currently recognized and many additional undescribed species known from museum collections (Albert, 2001;Albert et al, 2004;Albert and Crampton, 2005;Maxime and Albert, 2009;Richer-de-Forges et al, 2009). Species of Gymnotus exhibit considerable morphological and ecological diversity, ranging in mature body size over an order of magnitude (approx.…”

“…Gymnotus also has the widest geographic range of all gymnotiform genera, from southern Mexico (Albert and Miller, 1995) south to the pampas of northern Argentina (Casciotta et al, 1989). Gymnotus exhibits its highest diversity in the lowlands of western Amazonia from where 16 valid species are known Maxime and Albert, 2009). The diversity of Gymnotus in adjacent upland areas of the Andean Piedmont is less well known, due in part to logistic difficulties of sampling these remote regions, and perhaps also to more restricted range distributions in upland areas (Albert et al, 2011).…”

The Fitzcarrald Arch: A Vicariant Event for Chaetostoma (Siluriformes: Loricariidae) Speciation?

“…In the context of baseline studies, southeastern Peru has received special attention because of the presence of important oil and natural gas reservoirs in South America (Espurt et al, 2007). Based on the current taxonomic knowledge of the Peruvian fish fauna, researchers have suggested the possibility of finding undiscovered and undescribed species of freshwater fishes in remote and isolated highland areas (Ortega and Hidalgo, 2008), such as the slopes of the Fitzcarrald Arch (Maxime and Albert, 2009;Espurt et al, 2010), an elevational feature (400 to 600 m asl) that separates the foredeeps of the northern and southern Amazonian foreland basins (Regard et al, 2009).…”