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Teleostei (teleosts) > Gymnotiformes (Knifefishes) > Gymnotidae (Naked-back knifefishes) > Gymnotinae
Etymology: Gymnotus: Greek, gymnos = naked (Ref. 45335); varzea: Named for the whitewater várzea floodplain, which this species is restricted to..

Environment: milieu / climate zone / depth range / distribution range Ecology

Freshwater; benthopelagic. Tropical

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South America: Amazon basin in Brazil and Peru.

Size / Weight / Age

Maturity: L_m ? range ? - ? cm
Max length : 28.5 cm TL male/unsexed; (Ref. 55508); max. published weight: 65.00 g (Ref. 55508)

Short description Identification keys | Morphology | Morphometrics

Dorsal spines (total): 0; Dorsal soft rays (total): 0; Anal soft rays: 230 - 310. Distinguished from its congeners endemic to the Amazon and Orinoco Basins and the Guyana Shield in having a color pattern of 16-22 oblique dark pigment bands with wavy and irregular margins in which the majority of bands at midbody form X-shaped patterns (resembling metaphase chromosomes) and in which the dark bands are about twice as broad as the pale interbands. Further differs from its congeners in having the following unique combination of characters: clear (unpigmented) patch at the caudal end of the anal-fin membrane in specimens 6.0-23.7 cm; and bands never divided to form band pairs (Ref. 55508).

Facultative air-breathing in the genus (Ref. 126274); Found in root mats of floating meadows in floodplains (Ref. 55508). Gulps atmospheric air into the hypervascularized posterior chamber of its gas bladder (Ref. 55508). Feeds on small aquatic invertebrates such as chironomid larvae, insect nymphs and microcrustaceans (Ref. 55508).

Life cycle and mating behavior Maturities | Reproduction | Spawnings | Egg(s) | Fecundities | Larvae

Main reference Upload your references | References | Coordinator : Campos-da-Paz, Ricardo | Collaborators

Crampton, W.G.R., D.H. Thorsen and J.S. Albert, 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. Copeia 2005(1):82-99. (Ref. 55508)

IUCN Red List Status (Ref. 130435)

Least Concern (LC) ; Date assessed: 14 August 2020

CITES

Not Evaluated

CMS (Ref. 116361)

Not Evaluated

Threat to humans

Harmless

Human uses

FAO - Publication: search | FishSource |

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Estimates based on models

Phylogenetic diversity index (Ref. 82804): PD₅₀ = 0.5000 [Uniqueness, from 0.5 = low to 2.0 = high].

Bayesian length-weight: a=0.01000 (0.00244 - 0.04107), b=3.04 (2.81 - 3.27), in cm total length, based on all LWR estimates for this body shape (Ref. 93245).

Trophic level (Ref. 69278): 3.2 ±0.40 se; based on food items.

Resilience (Ref. 120179): High, minimum population doubling time less than 15 months (Preliminary K or Fecundity.).

Fishing Vulnerability (Ref. 59153): Low vulnerability (19 of 100).

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Gymnotus varzea Crampton, Thorsen & Albert, 2005