Taxonomy & naming
Paralithoxus stocki was described by Nijssen and Isbrücker in 1990. The species was originally placed in the genus Lithoxus; the parentheses around the authority reflect its subsequent transfer to the genus Paralithoxus, the combination now accepted by the Catalog of Fishes (Eschmeyer, CAS).
The genus belongs to the subfamily Hypostominae (the Lithoxus group, part of the former Ancistrinae) within the family Loricariidae. A complementary description with notes on biology and distribution was provided by Le Bail et al. (2000: 246). The specific name honours Dr Jan Hendrik Stock (1931–1997), a carcinologist at the Zoologisch Museum, Amsterdam.
Morphology
Paralithoxus stocki is a small loricariid, reaching about 2.5 in standard length (SL). The body is strongly depressed (flattened), a form characteristic of the Lithoxus group and well suited to life pressed against the substrate in flowing water.
Finer morphological diagnostics are given in the original description by Nijssen & Isbrücker (1990) and in Le Bail et al. (2000). No data on sexual dimorphism specific to this species has been published in the sources available here.
Habitat
The species occurs in South America, in the Maroni and Mana River basins of French Guiana. It is a tropical freshwater, demersal fish, and its flattened, rheophilic body form indicates an association with flowing, well-oxygenated water over a firm substrate.
Detailed water-chemistry measurements for its localities are not published in the sources available here.
Feeding
No data on the diet of Paralithoxus stocki has been published in the sources available here. Members of the Lithoxus group are small benthic loricariids generally understood to graze biofilm and small invertebrates from rocky surfaces, but specific feeding studies for this species are lacking.
Mating
No data on the courtship or mating behaviour of Paralithoxus stocki has been published in the sources available here.
Breeding
No data on the reproduction or breeding of Paralithoxus stocki has been published in the sources available here.
In the aquarium
Paralithoxus stocki is not established in the aquarium trade, and no husbandry data specific to it has been published in the sources available here. As a small, flattened, current-loving fish, it would by analogy with related rheophilic loricariids require cool, fast-flowing, highly oxygenated water, but this remains untested for the species.
Conservation
The IUCN Red List assessed Paralithoxus stocki as Least Concern (LC), with the assessment dated 19 October 2020 (IUCN Red List version 2025-2). The species occurs in the Maroni and Mana basins of French Guiana, and the assessment did not identify a level of threat warranting a higher category.