Taxonomy & naming
Harttiella pilosa was described by Raphaël Covain and Sonia Fisch-Muller in 2012 in the journal Cybium (volume 36, number 1, pages 115–161, Ref. 90209), as part of a broader revision of the genus Harttiella in the Guianas. The species is placed in the subfamily Loricariinae of the armoured catfish family Loricariidae. FishBase records it under SpecCode 66580, and the Catalog of Fishes (Eschmeyer, CAS) is the authority for the valid binomial.
The genus Harttiella comprises small, slender loricariins of the Guiana Shield, several of which are narrow-range endemics tied to individual upland streams. Harttiella pilosa is diagnosed from its congeners primarily by its distinctive hispid — literally 'hairy' — appearance, contrasting with the smooth to velvety body surface of related species, together with a shorter head, a deeper body, and diagnostic DNA barcode sequences reported in the original description.
Morphology
Harttiella pilosa is a small loricariin reaching only about 1.5 in standard length (the largest measured specimens are male or unsexed). The body is elongate and depressed, in the typical Loricariinae fashion, encased in rows of bony scutes. Fin-ray counts recorded in the original description are 7 dorsal soft rays, and an anal fin with 1 spine and 5 soft rays.
The defining feature is the hispid or 'hairy' texture — most pronounced on the male head — that sets the species apart from the smoother-bodied members of the genus and gave rise to the epithet pilosa. Relative to its congeners, H. pilosa also has a comparatively shorter head and a deeper body. No data on live coloration beyond the preserved type material is published.
Habitat
The species is known only from its type locality: Crique Grillon, a small tributary of the Orapu River in the Tortue Mountains of French Guiana. It was collected just downstream of a roughly 98 ft waterfall, in a stream about 33 ft wide carrying shallow, clear water. The substrate is a mix of gravel, pebbles, boulders, bedrock, and iron-hydroxide-stained sand.
FishBase characterises the species as freshwater and demersal, living in tropical conditions of about 75 °F and warmer, with a pH of roughly 6.5 and above. Its entire documented distribution is this single upland drainage — a degree of localisation that is central to its conservation status.
Feeding
No direct dietary study of Harttiella pilosa has been published. FishBase assigns a modelled trophic level of 2.8, consistent with the small loricariins of clear upland streams that graze biofilm, periphyton, and fine detritus from hard surfaces. Like other members of the subfamily, it is presumed to rasp the gravel, boulder, and bedrock surfaces of its stream for the algal and microbial film that coats them, but specific feeding observations remain undescribed.
Mating
No data on the courtship or mating behaviour of Harttiella pilosa has been published. The pronounced hispid texture of the male head suggests sexually dimorphic odontode development, a common feature in loricariids where males develop enhanced bristling during the reproductive season, but no breeding observations exist to confirm its function.
Breeding
No reproductive data for Harttiella pilosa has been published — there are no documented spawnings in the wild or in captivity, and clutch size, spawning site, and parental care are all unknown. Loricariins typically deposit adhesive eggs that are guarded by the male, but in the absence of direct observation this cannot be asserted for the species.
In the aquarium
Harttiella pilosa has no aquarium presence. As a Critically Endangered single-locality endemic of an upland French Guiana stream, it is not collected for the ornamental trade, and no husbandry information exists. Were it ever maintained, its native conditions point to cool, clear, well-oxygenated water over hard substrates at around 75 °F and a near-neutral to slightly acidic pH — but in practice this is a fish for conservation and scientific attention rather than the hobby.
Conservation
Harttiella pilosa is assessed by the IUCN Red List as Critically Endangered (CR) under criteria B2ab(iii), with the assessment dated 14 January 2021. The listing reflects an extreme restriction of range: the species is known only from Crique Grillon in the Tortue Mountains (Orapu drainage) of French Guiana, a single tiny locality. With such a confined distribution, any localised disturbance — habitat degradation, alteration of the stream, water-quality decline, or upstream mining and deforestation pressures common in the Guiana Shield — could threaten the entire known population at once. This is among the most precarious conservation statuses of any loricariid covered here, and the species warrants strict protection of its sole known stream.