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DoNascimiento et al 2026 (2)

Abstract: Among vertebrates, specialised scale-feeding occurs almost exclusively in tropical freshwater fishes, with the Amazon basin having the richest regional assemblage of such specialists. With 28 valid species and 11 valid genera, 10 of which are ectoparasitic scale and mucus-feeders, the Neotropical trichomycterid subfamily Stegophilinae is the only fish lineage to have significantly diversified within this niche. Stegophilines are widespread and ubiquitous throughout the lowland freshwaters of South America, east of the Andes. Description: We describe Arhinoglanis gen. nov. and Arhinoglanis reticulatus sp. nov., the first Stegophilinae from west of the Andes, from the upper Cauca River drainage, Colombia. At 26.4 mm maximum standard length, the new genus and species is also the first miniature Stegophilinae. Using diaphanization, light microscopy, and micro-computed tomography imagery, we coded 534 morphological characters for 50 terminal taxa to recover the new taxon as sister to the exclusively cis-Andean clade of Homodiaetus + Schultzichthys. A single unique synapomorphy unites these genera: proximal tip of ceratobranchial 5 wider than proximal tip of ceratobranchial 4. Five autapomorphies diagnose the new genus, the most notable of which is a paedomorphically unossified dorsal lamina of the mesethmoid (DoNascimiento et al. 2026). Habitat: Colombia, Risaralda Department, Río Risaralda, La Virginia Municipality, 1.3km downstream of confluence with quebrada Totui and 7.6km from mouth of Río Cauca, 04°53'38''N 75°53'12''W. Etymology: The genus name Arhinoglanis: From the Greek rhinos (snout) and glanis (catfish), in allusion to the missing bony dorsal lamina of the mesethmoid, distinguishing this genus from all other Trichomycteridae. Gender masculine. The specific name relictus: From the Latin relictum (relic) in reference to the isolated geographic distribution of this species as the sole member of Stegophilinae present in a trans-Andean River basin (west of the Andean Central cordillera). The specific epithet is used as an adjective (DoNascimiento et al. 2026).

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Trichomycteridae

South America: Colombia, Risaralda Department, Río Risaralda, La Virginia Municipality, 1.3km downstream of confluence with quebrada Totui and 7.6km from mouth of Río Cauca, 04°53'38''N 75°53'12''W.

2.0cm. (¾ins)

24 -27°c (75-81°f.)

6.0-7.0.

Carlos DoNascimiento, Armando Ortega-Lara, Juan G Albornoz-Garzón, César Román-Valencia, Nathan K Lujan, Phylogenetic assessment and taxonomic description of the first scale-feeding candiru from west of the Andes (Siluriformes, Trichomycteridae), Zoological Journal of the Linnean Society, Volume 206, Issue 3, March 2026, zlag002.
Fish in the News 2026.