Taxonomy & naming
Aphanotorulus phrixosoma was first described by Henry Weed Fowler in 1940. The species was later moved into Aphanotorulus as a new combination by Isbrücker and Nijssen in 1992, and the genus itself was revised by Ray and Armbruster in 2016 (Zootaxa 4072(5): 501–539, 'The genera Isorineloricaria and Aphanotorulus, with description of a new species'). The Catalog of Fishes (Eschmeyer, CAS) recognises Aphanotorulus phrixosoma (Fowler, 1940) as a valid name, with the authority placed in parentheses to reflect the change of genus from its original placement.
The species belongs to subfamily Hypostominae (tribe Hypostomini) within the armoured catfish family Loricariidae. No L-number or LDA code is associated with it, and it has no widely used common name in the hobby — consistent with a fish that is essentially a museum and ichthyological taxon rather than an aquarium import.
Morphology
The largest measured specimen recorded on FishBase is 4 in in standard length. Beyond overall size, no detailed published description of the live coloration or fin counts is summarised in the sources available here. As a member of Aphanotorulus, it shares the heavily armoured, depressed body and ventral suckermouth typical of the Hypostominae, and the genus as a whole is noted for facultative air-breathing — individuals can gulp atmospheric air to supplement gill respiration in low-oxygen water. A full morphological account would require consulting Ray and Armbruster's 2016 revision directly.
Habitat
Aphanotorulus phrixosoma is recorded from the upper Amazon drainage of Peru. FishBase characterises the species as a freshwater, demersal (bottom-associated), tropical fish. Specific data on the water chemistry, current, substrate, or seasonal conditions of its habitat have not been published in the sources available here. The facultative air-breathing reported for the genus is consistent with occupying warm lowland waters where dissolved oxygen can fall seasonally.
Feeding
No diet study specific to Aphanotorulus phrixosoma has been published. Like other Hypostominae, it is presumed to be a benthic grazer, rasping biofilm, algae, and fine organic detritus from submerged surfaces with its suckermouth, but this is inference from the subfamily rather than a documented observation for this species.
Mating
No data has been published on courtship or mating behaviour in Aphanotorulus phrixosoma.
Breeding
No data has been published on the reproduction of Aphanotorulus phrixosoma. Its spawning mode, clutch size, and any parental care remain undocumented in the sources available here.
In the aquarium
Aphanotorulus phrixosoma is not a fish of the ornamental trade, and no aquarium husbandry information has been published for it. Any keeping notes would be speculation; the species is best regarded as a wild taxon known chiefly from scientific collections rather than a hobby subject.
Conservation
The IUCN Red List assessed Aphanotorulus phrixosoma as Data Deficient (DD) on 3 December 2020, meaning there is insufficient information on its distribution, population, and threats to evaluate its extinction risk. No species-specific conservation measures are in place, and the principal need is basic field and population research.