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Calegari, B. B. et al. 2026 (1)

Description: Trachelyichthys displicatus differs from all congeners except T. gaiophanes, by having four free pterygiophores supporting the dorsal fin (vs. three free pterygiophores supporting the dorsal fin). The new species differs from all congeners, except T. exilis, by having a long posterior process of the coracoid, distinctly surpassing the end of the pectoral-fin base, to approximately one-third of the adpressed pectoral-fin spine (vs. short posterior process of the coracoid reaching approximately to the end of the pectoral-fin base); and from T. exilis by having the transformator process of the tripus extending well past the end of the Müllerian-ramus base, reaching to the proximal portion of the parapophysis of the fifth vertebra (vs. transformator process reaching to the end or slightly surpassing the base of the Müllerian ramus, never reaching the parapophysis of the fifth vertebra. Trachelyichthys displicatus is also distinguished from congeners, except T. exilis, by having a deeper body (depth at anterior nuchal plate 22.9–27.9 vs. 16.7–20.2% SL; distance from dorsal-fin origin to pectoral-fin origin 26.0–30.7 vs. 21.5–25.6% SL). The new species further differs from T. decaradiatus, T. exilis, and T. varii, by having dorsal procurrent caudal-fin rays reaching anteriorly to the tip of the neural spine of the sixth vertebra anterior to the caudal complex centrum (vs. procurrent rays reaching anteriorly to the tip of the fourth vertebra anterior to the caudal complex centrum). Trachelichthys displicatus further differs from T. gaiophanes and T. epachrus by lacking a ventrolateral expansion of the posterior nuchal plate (vs. posterior nuchal plate ventrolaterally expanded); and by the colour pattern composed of a pale cream to light brown ground colour with large darker irregular spots on the body (vs. uniform brown colouration of the body), (Calegari, B. B. et al. 2026). Habitat: The new species is known from several blackwater tributaries along the main channel of the Rio Amazonas basin and lower portions of the Xingu, Tapajós, Negro and Tefé rivers, near their confluences with the Rio Amazonas. Colouration: Overall colouration pattern strongly contrasting dark spots and light colouration, similar to preserved specimens, but body somewhat translucent. Aquarium Care: Keeping this species is not too much of a problem as long as the water is kept clean and not too alkaline with a p.H.of between 6.5 and 7.0. They do like a planted aquarium where they like to hide out during the day. Diet: In the aquarium a good mixture of dry food such as flake and tablet. Worm food such as bloodworm, whiteworm and grindal. Etymology: Trachelyichthys: trachely, referring to close similarity to and relationship with Trachelyopterus; ichthys; fish. The specific name displicatus: From the Latin displicos, masculine, meaning spread, well distributed, in allusion to the wider distribution of the species compared to congeners. An adjective.

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Auchenipteridae

South America: Rio Amazonas, in Amazonas and Pará States of Brazil.

7.0cm (2¾ins)

22-25°c (71-77°f.)

6.5-7.0.

Calegari, B. B., Akama, A., Ferraris Jr., C., & Reis, R. E.. (2026). Hidden diversity of the catfish genus Trachelyichthys (Siluriformes: Auchenipteridae): a revisionary study with description of four new species from the Amazon basin. Neotropical Ichthyology, 24(2), e250200.
Fish in the News 2026.