Taxonomy & naming
Curculionichthys insperatus was originally described by Heraldo A. Britski and Júlio C. Garavello in 2003 in Copeia (volume 2003, number 3, pp. 562–571) as Hisonotus insperatus, with accompanying comments on the genus Hisonotus and on the related genus Microlepidogaster. The Catalog of Fishes (Eschmeyer, CAS; genus id 11408, species id 67514) recognises the current valid combination Curculionichthys insperatus (Britski & Garavello, 2003), with the parenthetical authority reflecting the post-description generic transfer.
The transfer to Curculionichthys was effected by Fábio F. Roxo, Gleison S. C. Silva, Luz E. Ochoa, and Cláudio Oliveira in 2015 in ZooKeys (volume 534, pp. 103–134). Their phylogenetic analysis of Hypoptopomatinae demonstrated that the species previously lumped within Hisonotus sensu lato formed several distinct, non-monophyletic lineages; Curculionichthys was erected as a new genus to accommodate a clade sharing a distinctive elongated snout. The genus name compounds the Latin curculionem (weevil or elongated snout) with the Greek ichthys (fish), translating approximately as 'weevil-fish' or 'long-snouted fish'. The species epithet insperatus is Latin for 'unexpected', reflecting the authors' surprise at finding a morphologically distinctive new species within material previously considered to belong to known Hisonotus taxa.
Morphology
Curculionichthys insperatus is a miniature loricariid, reaching a maximum recorded standard length of 1 in. The body is stocky by Hypoptopomatinae standards, covered in bony scutes arranged in the overlapping rows typical of the subfamily. The snout is elongated — the trait that anchors the genus name — and the rostral plate pair covers the snout tip, a diagnostic character of the genus.
From its original description, C. insperatus is distinguished from all other members of the Hisonotus complex (now reassigned across several genera) by a combination of features: the rostral plate pair covering the snout tip; the lateralis canal present in almost every plate along the body length; a lateral line that is almost complete and largely uninterrupted, with approximately 22 perforated plates plus one to three plates lacking the canal; a smooth pectoral spine lacking odontodes on the posterior dorsal margin for more than half of its width; and a scapular bridge that is completely exposed or bears only a very reduced median arrector fossae. Dorsal soft rays number 8 and anal soft rays 6. Coloration in life is not fully characterised in the available literature but is presumed to be the typical mottled brown of hypoptopomatine catfishes.
Habitat
Curculionichthys insperatus is known from the upper Rio Paraná drainage of Brazil. Within the Paraná basin it inhabits streams where banks are covered by partially submerged vegetation — a microhabitat description that places it in the marginal zone of small to medium watercourses, clinging to root tangles, submerged grasses, and low branches trailing into the current.
This vegetation-bank association is characteristic of many small hypoptopomatine catfishes, which exploit the dense surface area offered by root systems and submerged plant material as both refuge from predators and rich grazing ground for the algal and detrital films that form there. Water conditions in upper Paraná streams are tropical, typically soft to moderately hard, and clear to slightly turbid depending on season and local geology.
Feeding
Like other members of Hypoptopomatinae, C. insperatus is an aufwuchs and biofilm grazer. Its ventral sucking disc and fine teeth are adapted for scraping the thin layer of algae, diatoms, bacteria, and fine organic matter from hard and semi-hard surfaces — roots, submerged stems, smooth stones, and woody debris.
In the aquarium, small sinking algae wafers, spirulina-enriched foods, and the natural biofilm of a mature, well-lit tank provide appropriate nutrition. Soft blanched vegetables such as cucumber and courgette may be accepted. At 1 in maximum length, the mouth is very small and food particle size must be matched accordingly. This species will not compete effectively for food against larger, more aggressive catfishes.
Mating
No specific courtship observations for C. insperatus are recorded in the available literature. By analogy with other small hypoptopomatine catfishes, males are likely distinguished by the development of odontodes on the snout, cheeks, or pectoral spines during the breeding season, which may function in male-male competition or female assessment. The elongated snout of this genus may play a role in close-range signalling, though this is speculative.
Given the species' small size and its association with vegetation banks, spawning likely occurs in sheltered microhabitats within dense root or plant matrices.
Breeding
No breeding records for Curculionichthys insperatus in captivity are documented in the available literature. The species is essentially unknown in the hobby. By inference from related hypoptopomatine genera, a cave or crevice-spawning strategy with paternal or biparental guarding of a small adhesive egg clutch is plausible, but nothing specific can be stated with confidence.
Successful captive breeding of this species, should it ever become available, would likely require a species tank with fine, mature substrate, dense plant or root structure mimicking its natural bank habitat, soft and slightly acidic tropical water, and a diet of quality fine-particle algae and biofilm.
In the aquarium
Curculionichthys insperatus is not established in the ornamental trade and is effectively unknown to hobbyists. At a maximum of 1 in SL it is among the smallest loricariids, and any captive maintenance would require conditions tailored to its tiny size and vegetation-bank ecology.
If specimens were to be obtained, a small, heavily planted or well-structured aquarium with soft water, tropical temperatures, and an established biofilm would be the appropriate environment. Competition from larger or more assertive tankmates would likely prevent the species from feeding adequately. A biotope or species setup oriented around the upper Paraná riparian zone — fine substrate, trailing plant roots, gentle flow — would best replicate its wild conditions.
Conservation
The IUCN Red List assessed Curculionichthys insperatus as Least Concern in November 2018. The assessment reflects the species' presence within the upper Paraná drainage and no documented population-level threats at the time of evaluation.
The upper Paraná basin has been heavily altered by dams, water extraction, agriculture, and urbanisation, and the vegetation-bank microhabitat on which small hypoptopomatines depend is particularly vulnerable to riparian deforestation and stream bank clearing. The small size and apparent habitat specificity of C. insperatus could make local populations vulnerable to such changes even where the broader assessment status remains favourable.