Gymnotus arapaima Albert & Crampton, 2001

Family:  Gymnotidae (Naked-back knifefishes), subfamily: Gymnotinae
Max. size:  55 cm TL (male/unsexed); max.weight: 450.0 g
Environment:  demersal; freshwater; pH range: 6.30000019073486 - 7.19999980926514
Distribution:  South America: Mamirauá lake system, Lago Tefé, and terra firme swamps near the town of Tefé in Central Amazonia.
Diagnosis:  Possess reverse counter shading (lighter on top) in which the dark bands are interrupted dorsally and the pale interband regions merge on the dorsum and in which the dorsum has a silver-blue sheen in life, and very large anterior nares (diameter about that of eye), associated with a large cleft in the anterolateral margin of the ethmoid region resulting in a square anterior margin of snout between the anterior nares. With deep body (body depth 11-13% TL versus 6-10): long head (head length 12.7-13.6% TL versus 8.8-12.6), and depressed head (head depth 53-57% TL versus 58-64) (Ref. 41292).
Biology:  Juveniles commonly collected in várzea floating meadows, adults in várzea flooded forest but rarely caught in floating meadows where they are presumed to spawn.
IUCN Red List Status: Least Concern (LC); Date assessed: 12 August 2020 Ref. (130435)
Threat to humans:  harmless


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