Editorial Type:
Article Category: Research Article
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Online Publication Date: 01 Feb 2005

Three New Species from a Diverse, Sympatric Assemblage of the Electric Fish Gymnotus (Gymnotiformes: Gymnotidae) in the Lowland Amazon Basin, with Notes on Ecology

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Page Range: 82 – 99
DOI: 10.1643/CI-03-242R2
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Abstract

Three new sympatric species of the Neotropical electric fish Gymnotus (Gymnotidae) are described from the lowland Amazon Basin at localities near Tefé (Brazil) and Iquitos and Jenaro Herrera (Peru). These taxa are described using features of external morphology, meristics, pigmentation, osteology, electric organ morphology, and the electric organ discharge. This paper concludes the documentation of the diversity of Gymnotus from the region of Tefé, near the confluence of the Rio Solimões (Amazon) with the Rio Japurá. The three new species described here bring to eight the number of species of Gymnotus originally described from the Tefé region, and to 11, the total number of species of Gymnotus in this region. Two of the new species described here, Gymnotus obscurus n. sp. and Gymnotus varzea n. sp., are known only from the Quaternary whitewater floodplain (várzea) of the Rio Amazon and/or Río Ucayali. The third new species reported, Gymnotus curupira n. sp., is restricted to the terra firme Tertiary peneplain and mainly inhabits isolated swamp pools in the rain forest, which it can reach by moving over-land through moist leaf litter.

Três espécies novas, e simpátricas, são descritas do gênero de peixes elétricos Neotropicais, Gymnotus (Gymnotidae). Estas espécies, provenientes de localidades próximas às cidades de Tefé (Brasil) e de Iquitos e Jenaro Herrera (Perú) na Bacía Amazônica, são descritas com base em características de morfologia externa, dados merísticos, pigmentação, osteologia e propriedades das descargas do órgão elétrico (DOE). Este artigo conclui a documentação da diversidade de Gymnotus da região de Tefé, próxima à confluência dos Rios Solimões e Japurá. Onze espécies de Gymnotus têm sido encontrada na região de Tefé, das quais oito foram descritas com base em material desta própria região. Duas das espécies descritas aqui, Gymnotus obscurus n. sp. e Gymnotus varzea n. sp., ocorrem exclusivamente em várzeas (planícies sazonalmente alagáveis de rios de água branca) do Rio Solimões e/ou do Río Ucayali. A terçeira espécie, Gymnotus curupira n. sp., é encontrada exclusivamente em sistemas de terra firme e é comum em poços isolados de água na floresta. Gymnotus curupira é capaz de percorrer distâncias pequenas entre igarapés e tais poços por terra, através de liteira húmida.

Copyright: The American Society of Ichthyologists and Herpetologists
 Fig. 1. 
 Fig. 1. 

Map of Tefé area, Brazil showing positions of the holotype localities of 1, Gymnotus curupira n. sp.; 2, Gymnotus obscurus n. sp.; 3, Gymnotus varzea n. sp. Areas exposed to an annual flood regime are stippled. Quaternary floodplain systems: (A) whitewater floodplain (várzea) lake; (B) seasonally inundated forest; (C) cano (seasonally flowing channel draining várzea); (D) paraná (channel connected at both ends to main river channel). Tertiary terra firme systems: (E) terra firme streams, (F) ephemeral rain-forest swamps. See Crampton (1998b) for detailed description of habitats A–E. MSDR = Mamirauá Sustainable Development Reserve. Base map traced from 1999 1: 150,000 Landsat TM5 images. Extent of annual flooding plotted from June 1995 NASDA JERS-1 image

 Fig. 2. 
 Fig. 2. 

Total length (TL) versus head length as a percentage of TL (HL%) for three species of Gymnotus from the Amazon Basin showing adult (solid symbol) and juvenile (open symbol) head proportions. Size of morphological maturity (adult size) is inferred from the inflection of these plots, which is in all species 120 mm TL. Most individuals achieved reproductive maturity at a larger size. Gymnotus curupira n. sp. = squares, solid line; Gymnotus obscurus n. sp. = circles, long dashes; Gymnotus varzea n. sp. = triangles, short dashes

 Fig. 3. 
 Fig. 3. 

Diagrammatic representation of body outlines and squamation of the holotypes of three new species of Gymnotus: (A) Gymnotus curupira n. sp., MZUSP 60607; (B) Gymnotus obscurus n. sp. MZUSP 60604; (C) Gymnotus varzea n. sp. MZUSP 60601. Arrows indicate position of anus. Scale bars = 10 mm

 Fig. 4. 
 Fig. 4. 

Gymnotus curupira n. sp. A1 (head) and A2 (body), MZUSP 75150; B, MZUSP 60609, WGRC 01.191199. Scale bars = 10 mm

 Fig. 5. 
 Fig. 5. 

Electric Organ Discharge (EOD) waveforms of sexually immature adult specimens of three new species of Gymnotus. EODs plotted head-positive upwards and scaled to the same peak-to-peak height and time base. Scale bar = 5 mm. (A) Gymnotus curupira n. sp. MZUSP 75145; (B) Gymnotus obscurus n. sp. UF 118836; (C) Gymnotus varzea n. sp. BMNH 1998.3.12.11

 Fig. 6. 
 Fig. 6. 

Part of South America showing collection records of three new species of Gymnotus: Gymnotus curupira n. sp. = squares; Gymnotus obscurus n. sp. = circles; Gymnotus varzea n. sp. = triangles. Open symbols are type localities. Some symbols represent more than one lot or locality. Base map by M. Weitzman

 Fig. 7. 
 Fig. 7. 

Gymnotus obscurus n. sp. A1 (head) A2 (body), MZUSP 75152; B, UF 118833, WGRC 11.030597. Scale bars = 10 mm

 Fig. 8. 
 Fig. 8. 

Gymnotus varzea n. sp. A1 (head) and A2 (body), INPA 18423; B, MZUSP 75160. Scale bars = 10 mm

Contributor Notes

Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611-7800. Present address: (DHT) Department of Zoology, Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, Illinois 60605-2496. E-mail: (WGRC) willc@flmnh.ufl.edu Send reprint requests to WGRC.

Accepted: 09 Sept 2004
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