Taxonomy & naming
Isorineloricaria acuarius was formally described by Ray and Armbruster in 2016, in their revision of the genera Isorineloricaria and Aphanotorulus published in Zootaxa (volume 4072, number 5, pages 501–539). The holotype was collected in the Río Portuguesa, part of the Orinoco drainage of Venezuela. The Catalog of Fishes (Eschmeyer, CAS) recognises the name as valid, with a species link present.
The species sits within the subfamily Hypostominae of the family Loricariidae, following the placement adopted by FishBase. Its description was part of a broader effort to clarify the limits of a group of loricariids whose generic assignment had long been unstable.
No data on indigenous or hobby common names has been published; the species is not a regular feature of the ornamental trade.
Morphology
Adults reach approximately 8 in standard length (SL) per the type series. Like other members of the genus, the body is encased in the overlapping bony scutes characteristic of loricariid catfishes.
The most notable morphological feature described for this species is found in nuptial males, which bear hypertrophied breeding odontodes — enlarged, spine-like dermal teeth. It is this dense, needle-bearing condition that gives the species its name. Detailed published colour and finer meristic descriptions beyond the original revision are sparse, and no living-specimen photographs were available in the consulted sources.
Habitat
Isorineloricaria acuarius is a freshwater, demersal, tropical species. It appears to be restricted to white waters within the Orinoco drainage of Venezuela. The holotype was collected on a sandy run with moderate flow, suggesting an association with current-swept sand substrates rather than still backwaters.
Beyond the type-locality conditions, no quantitative water-chemistry data (temperature, pH, hardness, depth) has been published for this species.
Feeding
No detailed dietary data has been published for Isorineloricaria acuarius. As a hypostomine loricariid it is presumed to graze biofilm, algae, and associated detritus from submerged surfaces in the manner typical of the subfamily, but this has not been confirmed by published gut-content or field observation for this species. Data is sparse.
Mating
Published reproductive information is limited. The presence of hypertrophied breeding odontodes on nuptial males indicates that males develop seasonal nuptial ornamentation, as is typical of the family. January appears to fall within the spawning period, inferred by analogy with the related Aphanotorulus ammophilus. No direct observations of courtship behaviour have been published.
Breeding
No spawning has been documented in captivity, and no clutch size, egg description, or parental-care details have been published for Isorineloricaria acuarius. As with many loricariids, paternal cave-brooding would be a reasonable expectation, but this is not confirmed for this species. Data is sparse.
In the aquarium
Isorineloricaria acuarius is not a species of the ornamental trade and no aquarium husbandry has been documented. Any keeping notes would be speculative. Given its origin in white-water rivers with moderate flow over sand and an adult size around 8 in SL, an aquarist encountering it would reasonably aim for warm, well-oxygenated water with strong current and a sand substrate, but no published care record exists to confirm these requirements.
Conservation
The IUCN Red List assessed Isorineloricaria acuarius as Least Concern, with the assessment dated 17 August 2020. No specific threats have been highlighted in the consulted sources. As a Venezuelan white-water endemic, it would share in the general pressures facing the Orinoco basin — agricultural runoff, sedimentation, and hydrological alteration — but at present it is not considered threatened.