Gymnotus obscurus Crampton, Thorsen & Albert, 2005
No Picture Available

 Family:  Gymnotidae (Naked-back knifefishes)
 Max. size:  21.5 cm TL (male/unsexed)
 Environment:  benthopelagic
 Distribution:  South America: varzea floodplain at the conflluence of the Rio Solimoes (Amazon) and the Rio Japura in Mamiraua Reserve near the Tefé, Amazonas, Brazil.
 Diagnosis:  Dorsal spines (total): 0-0; Dorsal soft rays (total): 0-0; Anal soft rays: 210-250. Distinguished from its congeners endemic to the Amazon and Orinoco Basins and the Guyana Shield in having many pectoral-fin rays 20-22; and a color pattern of oblique and undivided thin pale bands, less than one-quarter width of dark bands, with straight high-contrast margins, which extend to the dorsal midline on the anterior half of the body, and of which many are interrupted at the ventral margin of the hypaxial muscles along the anterior two-thirds of the body. Differs further from congeners endemic to the Amazon-Orinoco basins and the Guyana Shield in having the following unique combination of characters: clear (unpigmented) patch at the caudal end of the anal-fin membrane in specimens 6.0-23.5 TL; and bands never divided to form band pairs (Ref. 55508).
 Biology:  Inhabits root mats of floating meadows in floodplains. In the whitewater floodplain, juveniles are encountered in patches of floating macrophytes along lakes margins and along the edge of canos (drainage channels from lakes to the main river channels) and paranás (channels connected at both ends to the main river channel that transport whitewater through the floodplain). Floating macrophytes form extensive floating meadows. Undertakes aerial respiration by gulping atmospheric air into the hypervascularized posterior chamber of the gas bladder. Feeds primarily on chironomid larvae, small insect nymphs and small crustaceans (Ref. 55508).
 IUCN Red List Status: Not Evaluated  (Ref. 96402)
 Threat to humans:  harmless
 Country info:   
 

 Entered by: Torres, Armi G. - 26.09.05
 Modified by: Torres, Armi G. - 28.09.05

Source and more info: www.fishbase.org. For personal, classroom, and other internal use only. Not for publication.


Page created by Jen, 05.08.02, php script by kbanasihan 06/09/2010 ,  last modified by dsantos, 20/08/10