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Tridensimilis magnus Canto, Datovo, Ohara, Pinna, & Ribeiro. 2026

Image contributors to this species:

Canto, A. L. C et al 2026 (1)

ScotCat Sources:

Other Sources:

Relevant Information:

Abstract: A new species of translucent catfish of the genus Tridensimilis is described from the upper and middle Rio Tapajós basin, states of Pará and Mato Grosso, Brazil. In addition, we redefine the taxonomic limits of the genus Tridensimilis and present evidence that questions the current generic placement of Tridentopsistocantinsi. The new species is distinguished from congeners by a set of morphological features, in combination: number of vertebrae, anal-fin rays, opercular and interopercular odontodes; eyes positioned laterally and oriented ventrally, slightly more visible in ventral than in dorsal view; and basipterygia fused at midline. Live specimens of the new species display ex situ atmospheric air capture at the water surface, resulting in the filling of the digestive cavity with air bubbles, a behavior recorded for the first time in any representative of Tridentinae. The new species is the largest currently known of the subfamily Tridentinae, with analyzed specimen reaching 34 mm of standard length. The new taxon likely increases the list of endemism in the Rio Tapajós basin. Habitat: Known from the upper and middle Rio Tapajós basin, including Rios Teles Pires, Jamanxim, das Tropas, and Pacu, and small left-bank tributaries (igarapés da Montanha, Limão, and Miaçu). Aquarium Care: Seldem kept in the Aquarium due to their plain appearance and there preference to hide. Needs a substrate of fine gravel or mulm. Diet: Daphnia and mosquito larvae. Etymology: The specific name magnus: Latin meaning “large” or “great”, in allusion to the longer length of the species in comparison to its congeners, emphasising one of the distinctive morphological traits that diagnose the species. An adjective.

Common Name:

None

Synonyms:

None

Family:

Trichomycteridae

Distribution:

South America: igarapé Branco, tributary to Rio Aruri Grande, Rio Jamanxim drainage, Rio Tapajós drainage, Pará State, Brazil.

Size:

3.5cm. (1½ins)

Temp:

24-27°c (75-81°f.)

p.H.

6.0-7.0.

IUCN Red List

Not Evaluated.

Reference:

Canto, A. L. C., Datovo, A., Ohara, W. M., Pinna, M. C. C. de ., & Ribeiro, F. R. V. (2026). A new species of Tridensimilis (Siluriformes: Trichomycteridae) from Tapajós basin: the largest translucent catfish species of Tridentinae. Neotropical Ichthyology, 24(2), e250209.
Fish in the News 2026.

Family: Trichomycteridae Back to Ident-A-Cat Click on Thumbnails

Tridensimilis magnus
Lateral view-igarapé Branco, tributary to Rio Aruri Grande, Rio Jamanxim drainage, Rio Tapajós drainage, Pará State, Brazil

Tridensimilis magnus
Dorsal view-igarapé Branco, tributary to Rio Aruri Grande, Rio Jamanxim drainage, Rio Tapajós drainage, Pará State, Brazil

Tridensimilis magnus
Ventral view-igarapé Branco, tributary to Rio Aruri Grande, Rio Jamanxim drainage, Rio Tapajós drainage, Pará State, Brazil

Tridensimilis magnus
Arrows indicate swallowed air bubbles in stomach and intestines

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