Taxonomy & naming
Hemiancistrus chlorostictus was described by Cardoso and Malabarba in 1999 in Comunicações do Museu de Ciências da PUCRS, Série Zoologia (volume 12, pp. 144, figures 2–3), from specimens collected at the Passo Fundo dam (Gerasul UHPF, Ronda Alta, Rio Grande do Sul, Brazil; approximately 27°40'S, 52°45'W). The Catalog of Fishes (Eschmeyer, CAS; species ID 65564) recognises Hemiancistrus chlorostictus Cardoso & Malabarba, 1999 as the valid name.
The species belongs to the genus Hemiancistrus within tribe Ancistrini, subfamily Hypostominae. Molecular work on the group — mitochondrial D-loop sequences incorporated into a phylogeny of Hypostomus and related genera by Montoya-Burgos and Weber (GenBank AJ318350) — has placed H. chlorostictus within a broader Hypostominae context, though a comprehensive revision of Hemiancistrus remains in progress in the broader systematic literature.
H. chlorostictus is closely related to H. punctulatus and H. megalopteryx, with which it forms a morphological cluster of southern Brazilian Hemiancistrus. No L-number has been assigned, and the species has no established common name in the trade.
Morphology
Adults reach a maximum recorded size of 6 in standard length (SL) — a mid-range size for Hemiancistrus, smaller than the congener H. punctulatus (7.5 in SL) but similar in general body plan. Total length would add approximately 20% to the SL figure.
The genus-level body form is a depressed, dorsoventrally flattened loricariid with overlapping bony scutes covering the flanks and dorsal surface. In H. chlorostictus the ground colour is described as bearing a green-spotted pattern — the feature directly encoded in the species name (chloro = green; stictus = spotted). This coloration distinguishes it externally from the pale-spotted H. punctulatus, which has whitish rather than greenish spots against a dark body.
Sexual dimorphism follows the general Hemiancistrus pattern: adult males and females can be distinguished by body width (females are broader-bodied when gravid) and differences in the genital papilla. Males do not develop the elaborate branched rostral tentacles seen in Ancistrus.
Habitat
Hemiancistrus chlorostictus is known only from the Passo Fundo reservoir in the upper Uruguay River drainage, Rio Grande do Sul, Brazil. FishBase explicitly notes that the species is known only from the type locality, and this is corroborated by PlanetCatfish, which lists no additional collection localities. The reservoir was created by the Passo Fundo hydroelectric dam (operated by Gerasul) on the upper Uruguay tributary system.
The upper Uruguay River flows through the subtropical Planalto Sul-Riograndense, a highland plateau landscape with mixed Araucaria forest. Waters in this system tend toward cooler temperatures than Amazonian rivers, with seasonal variation driven by the region's subtropical climate. The conversion of the original river section into a reservoir has fundamentally altered the physical habitat — replacing lotic (flowing) conditions with a lentic (still) impoundment — and this habitat transformation is directly relevant to the species' conservation status.
Feeding
No dietary data specific to Hemiancistrus chlorostictus are available in the published literature. Based on its genus placement, H. chlorostictus is expected to function as an algae and aufwuchs grazer, using its oral disc and fine teeth to rasp biofilm, epilithic algae, and periphyton from rock and wood surfaces. Some supplementation with detritus and small invertebrates is consistent with the feeding strategy of related Hemiancistrus species.
In a reservoir environment, substrate and food availability may differ substantially from the original riverbed habitat, potentially including softer sediment substrates and altered algal communities. How well H. chlorostictus has adapted to these conditions since impoundment is not documented.
Mating
No mating or courtship observations have been published for Hemiancistrus chlorostictus. The species is not represented in the aquarium hobby and has not been bred in captivity. Given the complete absence of observational data, reproductive behaviour can only be inferred at the genus level: Hemiancistrus species are broadly expected to exhibit cave-spawning behaviour with male site defence. No species-specific confirmation is available.
Breeding
No breeding data for Hemiancistrus chlorostictus exist in the scientific or hobbyist literature. PlanetCatfish records no spawning attempts, and there are no known aquarium imports. As with mating, only genus-level inferences are possible: Hemiancistrus species are presumed to be paternal cave-brooders following the widespread Hypostominae reproductive pattern, but clutch size, incubation duration, and fry development specifics are undocumented for this species.
In the aquarium
Hemiancistrus chlorostictus does not appear to have entered the ornamental fish trade at any point. PlanetCatfish records no keepers, no spotters, and no imports. Its geographic isolation at a single reservoir in interior Rio Grande do Sul effectively places it outside the collection routes used for ornamental exports.
Should specimens become available through conservation-minded captive-breeding efforts, the cool subtropical origin of the species would suggest that aquarium temperatures well below the tropical norm — perhaps 64–75 °F — would be appropriate. Hard substrates, driftwood, and cave structures would be expected requirements. These parameters are extrapolated from habitat data; no aquarium trials are documented.
Conservation
Hemiancistrus chlorostictus is assessed as Near Threatened (NT) under criterion B1b(iii) on the IUCN Red List, evaluated on 7 November 2018. The NT designation reflects the species' extreme range restriction: it is known from a single location, the Passo Fundo reservoir in the upper Uruguay River, and has not been recorded elsewhere despite the description dating to 1999.
The IUCN criterion B1b(iii) indicates that the species has a restricted extent of occurrence and that the quality of its habitat is subject to ongoing decline — in this case, driven by the management regime of the Passo Fundo hydroelectric dam. Dam operations control water level, flow, temperature regimes, and sediment dynamics within the reservoir, all of which influence habitat quality for a benthic loricariid. Any significant drawdown, alteration of operating rules, or dam infrastructure failure would represent a direct threat to the only known population.
The combination of a single-site range and dependence on dam-managed habitat makes H. chlorostictus one of the more conservation-sensitive members of its genus, even though it falls just short of the Vulnerable threshold under current data.