Taxonomy & naming
Hypostomus ericius was described by Jonathan W. Armbruster in 2003 in Zootaxa (No. 249), as part of his revision of the Hypostomus cochliodon group. The type locality is in the Río Marañón drainage, approximately 1 mi upstream of Caterpiza, Peru. The Catalog of Fishes (Eschmeyer, CAS) recognises Hypostomus ericius Armbruster, 2003 as valid, placed in subfamily Hypostominae.
H. ericius is one of four new species erected in the 2003 revision alongside H. hemicochliodon, H. pagei, and H. sculpodon. It belongs to the H. cochliodon group, a clade of Hypostomus characterised by progressive spatulation of the teeth associated with a wood-eating habit. Within that group, H. ericius is diagnosed from all other members by its distinctive coloration: light tan-gray with well-separated spots and no stripes. The absence of a buccal papilla and the strongly developed sharp keels on the lateral plates further distinguish it. No L-number has been assigned.
Morphology
H. ericius reaches a recorded maximum of 7.5 in standard length (SL). The body follows the typical Hypostomus pattern — dorsoventrally compressed, with a broad, depressed head, a large triangular dorsal fin, and the trunk encased in bony scutes arranged in regular longitudinal rows. The defining external characteristic is the keels on the lateral plates: these are described as strong and sharp, projecting noticeably from the body surface and giving the fish the spiny, hedge-hog-like texture that inspired the species name.
Coloration in life is light tan-gray with well-separated, rounded darker spots distributed across the body and fins. Crucially, no stripes are present — an absence that distinguishes H. ericius from several sympatric Hypostomus species. The buccal papilla, a fleshy projection inside the mouth present in some related species, is absent in H. ericius.
The teeth are spatulate to a degree consistent with cochliodon group membership, enabling some wood-rasping capacity. Dimorphism is consistent with the genus: breeding males develop elongated odontodes on the interopercular region and pectoral fin spines; females show a broader body profile when gravid.
Habitat
H. ericius is known from the upper Río Amazonas drainage in Peru, specifically the Marañón drainage, with additional specimens recorded from the Ucayali Department (Río Breu basin). Its range is therefore restricted to the western Peruvian Amazon, making it considerably more geographically constrained than the wide-ranging H. hemicochliodon described in the same revision.
The Marañón and its tributaries in this region carry clear-to-turbid water depending on season, with water parameters influenced by Andean inputs. The species is demersal and freshwater, inhabiting the river bottom. As a facultative air-breather it can supplement aquatic respiration with atmospheric oxygen, an advantage during seasonal low-water periods when dissolved oxygen in still or slow water may decline. Precise microhabitat data (current speed, substrate type, depth range) have not been published for this species.
Feeding
As a member of the H. cochliodon group, H. ericius is expected to have some capacity for rasping wood and the biofilm communities colonising submerged surfaces. Its spatulate teeth permit this mode of feeding, though the degree of xylophagous specialisation relative to other group members is not precisely characterised in the available literature.
In the aquarium, a diet similar to that appropriate for other mid-sized cochliodon group Hypostomus is recommended: algae wafers, spirulina-based foods, blanched vegetables (courgette, sweet potato, cucumber), and access to softwood driftwood for grazing. Protein supplementation via frozen invertebrates can be offered in moderation. The distinctive keeled body form does not have feeding implications but does reflect a potentially more active, current-adapted lifestyle than smoother-bodied Hypostomus.
Mating
No published observations of courtship behaviour specific to H. ericius are available. General Hypostomus biology applies: males become territorial during the breeding season, defending cave sites or sheltered depressions, and develop more prominent interopercular odontodes as secondary sexual ornamentation. Rival males are repelled by fin-spreading displays and, if necessary, physical contact.
Given the species' moderate adult size (up to ~7.5 in SL), breeding-condition adults are potentially manageable in a large home aquarium with appropriate cave structures, though no captive breeding accounts are on record.
Breeding
No captive breeding records for Hypostomus ericius appear in the available literature or hobbyist sources. Based on the reproductive mode consistent across Hypostomus and the cochliodon group, cave-spawning with paternal brood care is the expected strategy: the male selects a sheltered cavity, spawning occurs on the cave walls, and the male fans and guards the adhesive egg clutch through hatching.
The maximum SL of 7.5 in places this species in a size class where breeding in a suitably equipped home aquarium would be theoretically feasible. No data on clutch size, incubation duration, or fry development are available for this species.
In the aquarium
H. ericius is an uncommon species in the ornamental trade and is unlikely to be encountered except as an incidental wild-caught import from Peru. Its maximum size of around 7.5 in SL (total length typically somewhat larger) places it in a manageable but not small category — a tank of at least 55 US gal with good filtration and flow is appropriate for an adult.
Water parameters matching its upper Amazonian origin are suitable: a temperature range broadly consistent with lowland Peruvian rivers, slightly acidic to neutral pH, and soft to moderately hard water. Driftwood should be provided both as enrichment and dietary supplement. Flat stones and PVC pipes or ceramic caves round out the furnishings.
The sharp lateral keels make handling with a net more difficult than with smoother loricariids — a sock-net or container is preferable when transfers are necessary, both to protect the fish and to avoid the keels catching net fibres. The species should be compatible with peaceful mid-water fish of appropriate size; cohabitation with other large loricariids in the same territory should be avoided.
Conservation
The IUCN Red List assessed Hypostomus ericius as Least Concern in April 2014. The species is known from the upper Río Amazonas drainage in Peru and no population declines triggering a threatened category have been identified at the time of assessment.
Its somewhat restricted range within the Peruvian Amazon — primarily the Marañón and Ucayali sub-drainages — means that localised threats such as deforestation, alluvial gold mining, and agricultural sedimentation in those river systems could have relevance for long-term population status. The Peruvian Amazon has experienced increasing land-use pressure in recent decades. At present, however, insufficient evidence of decline exists to move the species beyond Least Concern, and the 2014 assessment stands as the most recent evaluation.