All FishesAuchenipteridaeAuchenipterinaeAgeneiosus

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Scientific Name Ageneiosus inermis  (Linnaeus, 1766)
Common Name Slopehead Catfish
Type Locality Suriname.
Synonym(s) Ageneiosus armatus, Ageneiosus axillaris, Ageneiosus barranquenensis, Ageneiosus brevifilis, Ageneiosus dawalla, Ageneiosus gabardinii, Ageneiosus ogilviei, Ageneiosus sebae, Ageneiosus therezinae, Davalla schomburgkii, Hypothalmus dawalla, Silurus inermis
Pronunciation ah genie OH sus
Etymology Ageneiosus, from the Greek a, meaning without and genias, meaning beard in reference to the apparent lack of barbels. In fact, catfish of this genus have very short maxillary barbels that are almost indistinguishable to the human eye. 
Hop to next section Species Information
Size 590mm or 23.2" SL. Find near, nearer or same sized spp.
Identification Ageneiosus differs from other Auchenipteridae, except Tympanopleura, by having: 1, long bony process, narrowing distally on anterolateral border of sphenoid; 2, longitudinal groove on posterior margin of anterior fontanel (also present in Pseudepapterus); 3, dorsal portion of posttemporal-supracleithrum divided into two prominent branches; 4, internal and external processes of epioccipital sutured to parapophyses of fifth and sixth vertebrae; 5, bony process on posteromedial border of first infraorbital bone (also present in Tetranematichthys); 6, anterior or posterior region of second infra-orbital very curved; 7, bony expansion on laterodorsal margin of premaxilla; 8, operculum with spongy ossification; 9, bone projections on posterior extreme of the parurohyal; 10, seventh vertebra not fused to complex vertebrae (also present in Pseudepapterus); 11, well-developed crown of spines in proximal region of anterior margin of dorsal-fin spine of mature males; 12, short maxillary barbel, not extending posteriorly beyond snout (also present in Tetranematichthys); 13, mental barbels absent; 14, bony spines on maxillary barbel of mature males; 15, posterior lobes of testes reduced or absent (also present in Auchenipterus). Ageneiosus differs from Tympanopleura by having: 1, reduced and completely ossified gas bladder in adults, except Ageneiosus pardalis Lütken 1874 (v. large, non-ossified gas bladder during all phases of ontogenetic development); 2, posterior diverticula on the gas bladder absent (v. having paired posterior diverticula on the gas bladder, except T. piperata); 3, epaxial muscles almost completely covering the tympanic region in adults, except A. pardalis (v. tympanic region translucent, not covered by epaxial muscles); 4, dorsal process on the base of pectoral fin weakly developed, loosely articulating with cleithrum (v. dorsal process on the base of pectoral fin well developed, strongly articulating with cleithrum); 5, fenestra on the lateral wall of cleithrum (v. lateral wall of cleithrum completely ossified).

A key to the species of Ageneiosus is located here.

Body naked and elongated. Head is pointed and depressed at the top. Mouth is big and wide. The lateral eyes are situated along the level of the mouth, ensuring a vision above and below. Exhibits sexual dimorphism, like A. dentatus. The first ray of the dorsal fin is very long and has pointed spines
Sexing Observed in nuptial males. Predorsal profile distinctly more acutely angled upward than in females, juveniles and non-nuptial males. Maxillary barbel entirely ossified, forming a rigid, thickened, elongate barbel that may reach beyond the anterior eye margin when adpressed to the side of the head. Two rows of sharp recurved hooks on dorsal margin of barbel. Articular surface of maxilla expanded for contact with autopalatine. Dorsal-fin spine elongate, rigid, aculeiform, straight to strongly arched. Anterior margin of the dorsal-fin spine with pungent, unicuspid serrae, closely spaced proximally, recurved laterally, forming an enlarged, ossified protuberance at the anterior base of the spine; serrae distally arranged in a row, sometimes absent along middle quarter to third of spine. Dorsal-fin spine of nuptial males may be hyperextended anteriorly to approximately a 45∘ dorso-anterior angle, instead of the near-vertical limit of females and juveniles. The first branched dorsal-fin ray is much longer than in non-breeding males and females. Unbranched and first few branched anal-fin rays thickened and elongate to form a tubular intromittent organ bound by integument to the anterior margin of the anal fin. Urogenital opening of nuptial male displaced as a simple pore at the distal tip of intromittent organ.
Hop to next section Habitat Information
Distribution South America.
Amazon (click on these areas to find other species found there)
La Plata (click on these areas to find other species found there)
Amazon, Middle Amazon (Solimoes), Purus, Macap√° (click on these areas to find other species found there)
Guyana Waters, Coastal Rivers of Guyanas, Essequibo, Rupununi (click on these areas to find other species found there)

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IUCN Red List Category Not Evaluated
pH 6.5 - 7.8
Temperature 22.0-24.0°C or 71.6-75.2°F (Show species within this range)
Other Parameters dH 20.
Hop to next section Husbandry Information
Feeding Feeds on crustaceans and fishes.
Breeding Unreported in the aquarium.
Breeding Reports There is no breeding report.
Hop to next section Further Information
Reference Systema naturae sive regna tria naturae v. 1 (pt 1), pp 503.
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Last Update 2020 Sep 28 05:40 (species record created: 2003 Oct 08 00:00)