Taxonomy & naming
Harttia merevari was described in 2005 by Francisco Provenzano, Antonio Machado-Allison, Barry Chernoff, Philip Willink and Paulo Petry, in Neotropical Ichthyology (volume 3, number 4, page 520, figures 1–2). It has no synonyms — it was named directly into Harttia and has remained there, with the Catalog of Fishes (Eschmeyer, CAS) recognising the valid combination.
The type locality is the Caura River at the top of the Salto Pará waterfalls, in Bolívar State, Venezuela. Within the family Loricariidae the species belongs to the subfamily Loricariinae, the slender, dorsoventrally flattened whiptail catfishes with a long caudal peduncle and a ventral suckermouth. Its description was part of the broader effort to document the fish fauna of the Caura, an Orinoco tributary whose upland reaches were comparatively poorly surveyed before the AquaRAP-era inventories of the late 1990s and early 2000s.
Morphology
Harttia merevari is a small loricariine, with the type material reaching about 4 in standard length — considerably smaller than larger congeners such as H. fowleri. It has the characteristic Loricariinae body plan: strongly flattened, tapering to a slender caudal peduncle, and armoured with overlapping bony scutes, with a ventral suckermouth adapted to substrate grazing and to maintaining position in current.
The diagnostic morphometric and meristic characters separating it from other Harttia are given in the 2005 original description; beyond that account, little additional morphological information is available in the accessible literature. No species-specific data on sexual dimorphism has been published, though enlarged head and pectoral odontodes in breeding males are a recurring feature across the genus.
Habitat
The species is known from the upper Caura River of the Orinoco basin in Venezuela, near the Salto Pará falls — an upland, clearwater habitat. The Caura above Salto Pará is a relatively pristine highland river system draining the Guiana Shield, characterised by clear, soft, mineral-poor water running over rock. The fish's flattened body and suckermouth are consistent with life in flowing water on hard substrates.
No specific physico-chemical field measurements for H. merevari are published in the accessible sources, so precise temperature, pH and conductivity values for its habitat are undocumented; Guiana Shield clearwater rivers, however, are typically warm, very soft and acidic. The species is so far known only from this restricted upland reach, which is part of why it has been difficult to assess.
Feeding
No dietary study of Harttia merevari has been published, and FishBase notes that its diet is not specifically documented. As a ventral-mouthed loricariine of clearwater uplands, it is presumed to graze aufwuchs — the algal and biofilm film with its associated micro-invertebrates — on rock and gravel surfaces, supplemented by fine detritus. This follows the general feeding ecology of the genus and is consistent with the fish's morphology, but it is inference rather than recorded observation for this species.
Mating
Mating behaviour for Harttia merevari has not been documented. Within the genus, several species are substrate spawners in which the male guards the eggs, and breeding males commonly develop hypertrophied odontodes, but whether H. merevari follows this pattern is unknown from the accessible literature. No data published.
Breeding
No breeding account for Harttia merevari exists in the accessible sources, from the wild or in captivity. Substrate egg-laying with male guarding of an adhesive clutch would be the expected mode by analogy with related Harttia, but this is extrapolation rather than recorded fact for this species. It is effectively absent from the aquarium hobby and its reproduction remains entirely undocumented.
In the aquarium
Harttia merevari is not a fish of the aquarium trade; it carries no L-number and is known essentially only from scientific collection. No husbandry information specific to the species exists. Were it ever maintained, its highland clearwater Caura origin would imply a need for very soft, acidic, well-oxygenated flowing water over a hard substrate, with scrupulously clean conditions — the demanding regime typical of upland Guiana Shield rheophiles. In practice it should be regarded as a wild species of scientific rather than hobby interest.
Conservation
The IUCN Red List assessed Harttia merevari as Data Deficient in 2020. It is known only from a restricted upland reach of the Caura River within the Orinoco basin, and there is insufficient information on its population size, trends and threats to assign a more specific category. The upper Caura has remained relatively intact, but the broader Caura basin has faced pressures from illegal gold mining, which causes sedimentation and mercury contamination — a potential concern for a fish with such a narrow known range. Resolving its status will require targeted survey work in the upland Caura.