Taxonomy & naming
Otothyris juquiae was described by Garavello, Britski and Schaefer in 1998, one of the small-bodied members of the subfamily Hypoptopomatinae — the dwarf suckermouth catfishes that include the familiar otocinclus and their relatives. The genus Otothyris was erected for a handful of diminutive, broad-headed loricariids of the Atlantic coastal drainages of eastern Brazil.
The species epithet refers to the Rio Juquiá, a tributary within the Ribeira de Iguape river system from which the type material derives. The Catalog of Fishes (Eschmeyer, CAS) is the authority for the valid name; no junior synonyms of note are in circulation. The species sits within Hypoptopomatinae and is closely allied to the other two recognised Otothyris species, including the more widespread O. rostrata.
Morphology
This is a very small loricariid, reaching only about 1.5 in standard length. As in all Hypoptopomatinae, the body is encased in overlapping bony plates and the head is broad and flattened, with a ventral suckermouth adapted for clinging to substrate in flowing water. Detailed published colour and meristic descriptions are limited; the genus is characterised by a relatively short, deep body and the small adult size typical of the dwarf loricariid radiation.
No data on sexual dimorphism in this species has been published. In related dwarf loricariids, gravid females are typically broader-bodied when viewed from above, but this has not been documented specifically for O. juquiae.
Habitat
Otothyris juquiae is restricted to the Ribeira de Iguape River basin, including the Rio Juquiá, in southeastern Brazil. It is a freshwater, demersal species of tropical coastal drainages. Like other dwarf loricariids it is associated with the bottom and with submerged surfaces — rock, wood and vegetation — where the suckermouth allows it to graze and hold position in current.
Detailed water-chemistry measurements specific to its localities have not been published. The Ribeira de Iguape lies within one of Brazil's most heavily settled and industrialised coastal regions, and habitat condition is a central concern in the species' conservation assessment.
Feeding
No detailed feeding study has been published for Otothyris juquiae. By analogy with other Hypoptopomatinae, it is presumed to be a grazer of periphyton — the film of algae, diatoms, bacteria and fine detritus (aufwuchs) coating submerged surfaces — which it rasps with its ventral mouth. Specific dietary data for this species is not available.
Mating
No data on courtship or mating behaviour has been published for this species.
Breeding
No data on reproduction, spawning mode, clutch size or parental care has been published for Otothyris juquiae. Many dwarf Hypoptopomatinae deposit adhesive eggs on plant leaves or hard surfaces, but this has not been documented for O. juquiae, and no claims about its breeding can be made.
In the aquarium
Otothyris juquiae is essentially absent from the ornamental trade. There are no established aquarium husbandry reports, and given its Critically Endangered status and narrow range, it is not a species that should be targeted for collection. No reliable maintenance, water-parameter or breeding guidance specific to the species exists.
Conservation
The IUCN Red List assessed Otothyris juquiae as Critically Endangered in 2018 — among the most severe categories applied to any loricariid. The classification reflects a very restricted and fragmented distribution within the Ribeira de Iguape basin, a region subject to intense human pressure including urbanisation, agriculture, mining, water abstraction and pollution. A species in this category faces an extremely high risk of extinction in the wild.
Conservation of O. juquiae depends on protecting water quality and habitat integrity across the small set of drainages where it persists. Because the trade plays no meaningful role in its supply, the principal threats are environmental degradation of its native streams rather than collection. There is no captive-breeding programme to fall back on, which makes in-situ habitat protection the only realistic safeguard against loss of the species.