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Ben Lee (2)

Description: Ageneiosus intrusus differs from its congeners, except A. pardalis and A. ucayalensis, by having an upper jaw that overhangs the lower jaw by a distance greater than the hor-izontal eye diameter (v. less than the horizontal eye diameter). Ageneiosus intrusus differs from A. pardalis by having a reduced and ossified gas bladder (v. large, non-ossfied gas bladder) and by having epaxial musculature that covers the tympanic region (v.tympanic region translucent, not concealed by epaxial musculature). Ageneiosus intrusus differs from A. ucayalensis by having a robust pectoral spine, rigid and sharp(v. pectoral spine slender, becoming progressively segmented in individuals larger thanabout 100 mm LS) and fewer vertebrae (49 v. 53–55). Ageneiosus intrusus differs from A. lineatus by having more anal-?n rays (37– 46, mode=42 v. 32 –38, mode =34–35). Ageneiosus intrusus differs from A. inermis, A. magoi, A. polystictus and A. vittatus by having a deeply forked caudal ?n (v. caudal ?n strongly emarginate to truncate). Ageneiosus intrusus differs from A. apiaka by having more gill rakers on the firstbranchial arch (15– 20, mode =18 v. 13–16, mode =14) and by usually having a dark band on the distal margin of the caudal fin rays (v. distal margin of caudal fin rays hyaline). Specimens from the Orinoco River have an elongate premaxilla, but it overhangs the dentary by a distance slightly shorter than that of specimens from the Amazon River basin. These specimens are designated as non-types and no other differences in morphometric or meristic features were found when compared with specimens from the Amazon River basin. Sexual Differences: Males posses a genital papilla and when sexually mature have an enlarged and curved extension to the dorsal fin spine. They also grow thickened barbels to grasp the females with. These differences revert back to normal when not in season. Aquarium Care: As per this genera they will be fine as juveniles, but as they mature they become predatory so would need to be kept with fish that are not too small. A large tank would be needed with plenty of swimming space. Diet: Meat based. Etymology: The genus name Ageneiosus: beardless, pertaining to the very small maxillary barbels. The specifc epithet intrusus, from Latin, meaning intruded, in reference to the pre-maxilla projecting beyond the dentary, a distinctive character of the new species. Remarks: This genus was previously placed in its own family of Ageneiosidae and you can still find some publications that still follow this line.

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Auchenipteridae

South America: Middle and lower Amazon River and probably the Orinoco River. Type Locality: Rio Solimões, Paraná do Rei, Amazonas, Brazil.

15.0cm. (6ins)

23-26°c (73-79°f.)

6.5-7.2.

Mesa-Salazar, L. 2022. Ageneiosus intrusus. The IUCN Red List of Threatened Species 2022.
Ribeiro, Frank Rapp Py-Daniel, Lúcia Walsh, Stephen 2017/02/01. Taxonomic revision of the South American catfish genus Ageneiosus (Siluriformes: Auchenipteridae) with the description of four new species: taxonomic revision of ageneiosus 90 10.1111/jfb.13246 Journal of Fish Biology.