Gymnotus chimarrao Cognato, Richer-de-Forges, Albert & Crampton, 2008
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 Family:  Gymnotidae (Naked-back knifefishes)
 Max. size:  23.7 cm TL (male/unsexed)
 Environment:  benthopelagic
 Distribution:  South America: Arroio Grande in the Rio Taquari drainage, Brazil.
 Diagnosis:  Anal soft rays: 180-213. Distinguished from all 32 congeners except for some specimens (over 30.0 cm) of Gymnotus ardilai from the Río Magdalena drainage in northwest South America in having a pigmentation pattern in which the oblique dark-pigmented bands are faint, and difficult to distinguish from the ground color. Diagnosed from Gymnotus ardilai in having a shallower body depth (7.4-9.1 % TL [mean 8.2] vs. 11.4-13.2 [12.3]). Differs also from all species in the Gymnotus pantherinus species-group (and is placed in the Gymnotus carapo species-group) by the presence of two (vs. one) laterosensory canal pores in the preopercular-mandibular series of the dorsoposterior portion of the preopercle. Can be differentiated from all species in the Gymnotus carapo species-group that occur south of the Amazon basin except Gymnotus inaequilabiatus in having a much shallower body depth (7.4-9.1 % TL [mean 8.2] vs. 8.9-11.6 [mean 11.1] in Gymnotus bahianus, 9.8-10.3 [mean 10.1] in Gymnotus paraguensis, and 10.3-13.1 [mean 11.7] in Gymnotus sylvius). Differs further from Gymnotus inaequilabiatus in possessing a substantially narrower head (53.1-59.3 % HL [mean 57.5] vs. 65.3- 72.0 [mean 67.8]) (Ref. 75065). Description: Pectoral fin with single large anterior unbranched rays and 13-15 branched rays (Ref. 75065).
 Biology:  This species is known from a small stream, 1.5 m width, running through gallery forest in low hills, with altitude 54 m above mean sea level; substrate is mud and sand. All captured specimens were from marginal grasses rooted to the bottom of the stream in areas sheltered from the stream flow (with negligible current); dark-stained water; conductivity 107 ?S·cm-1, temperature 24.1 °C (Ref. 75065)
 IUCN Red List Status: Not Evaluated  (Ref. 96402)
 Threat to humans:  harmless
 Country info:   

 Entered by: Torres, Armi G. - 04.05.08
 Modified by: Bailly, Nicolas - 30.04.09

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