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.
Highlights
Gymnotus Linnaeus is the most species-rich genus of Neotropical electric fishes (Gymnotiformes) with 34 species currently recognized, and many additional undescribed species known from museum collections (Albert, 2001; Albert et al, 2004; Albert & Crampton, 2005; Lovejoy et al, 2009)
Gymnotus chaviro is described from the Alto Yuruá 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
Summary
Gymnotus Linnaeus is the most species-rich genus of Neotropical electric fishes (Gymnotiformes) with 34 species currently recognized, and many additional undescribed species known from museum collections (Albert, 2001; Albert et al, 2004; Albert & Crampton, 2005; Lovejoy et al, 2009). This park is located in poorly known region of high species endemism in southeastern Peru that straddles the headwaters of four of the largest tributary basins in the western Amazon; the Ucayali, Juruá (Yuruá), Purús and Madeira rivers. The upper reaches of these rivers are hydrologically isolated from one another across their watershed divides, and are at least partially isolated from the rest of lowland Amazonia by rapids and by distance This whole upland region is known as the Fitzcarrald Arch, and is thought to have been uplifted in association with Miocene-Pliocene rise of the Peruvian Andes (Westaway, 2006; Espurt et al, 2007). The description of the new species provided here is based on features of external morphology, pigmentation and osteology, and brings one more species to the G. carapo species group, and the total number of Gymnotus species to 35 (Table 1)
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