Taxonomy & naming
Paralithoxus planquettei was described by Marinus Boeseman in 1982, originally in the genus Lithoxus, and is recognised as valid by the Catalog of Fishes (Eschmeyer, CAS). It belongs to the Lithoxus group within subfamily Hypostominae, tribe Ancistrini, of the family Loricariidae.
The species honours Paul Planquette (1940-1996), a native of French Guiana associated with the INRA research station at Kourou. A complementary description and figures are provided by Le Bail et al. (2000:244) in their atlas of the freshwater fishes of French Guiana.
No aquarium L-number is associated with this species, and it is little known in the ornamental trade.
Morphology
Paralithoxus planquettei reaches approximately 3 in standard length, making it one of the larger members of its group described from the Guianas. As in other Lithoxus-group loricariids, the body is elongated and flattened, an adaptation to clinging to rock in strong current.
Detailed counts and proportional characters are given in Boeseman's original description and in the complementary account by Le Bail et al. (2000). No information on sexual dimorphism has been published for this species.
Habitat
Paralithoxus planquettei occurs in the Atlantic coastal drainages of French Guiana, from the Maroni to the Kaw river basins. It is a fish of stony rivulets, collected in small forest tributaries roughly three to four metres wide, of shallow depth, with rocky bottoms and strong current, often associated with cascades.
The species has been found during the dry season in nearly dry brooks alongside the killifishes Anablepsoides igneus and A. cladophorus (formerly Rivulus), an association that has led authors to characterise it as a pioneer species capable of colonising nutritionally poor environments. It is a freshwater, demersal, tropical fish and, like its congeners, a facultative air-breather — a useful adaptation in shallow brooks where oxygen and water levels fluctuate sharply through the season.
Feeding
No dedicated dietary study has been published for Paralithoxus planquettei. As a small, rasping, bottom-dwelling loricariid of stony brooks, it is presumed to graze the biofilm of algae, microorganisms and detritus that coats rocks in its habitat. Its reputation as a pioneer of nutritionally poor waters is consistent with an ability to subsist on sparse periphyton, but the specifics remain undocumented.
Mating
No data on courtship or mating behaviour have been published for this species.
Breeding
No data on reproduction, spawning mode or parental care have been published for Paralithoxus planquettei. It is not known to have been bred in captivity.
In the aquarium
Paralithoxus planquettei is not established in the aquarium hobby, and no husbandry experience has been documented. Its known ecology — shallow, rocky, fast-flowing forest brooks with cascades — implies that any attempt to keep it would call for strong current, high oxygenation, clean water and a rocky substrate. Beyond that general inference, no keeping recommendations can be made without inventing detail.
Conservation
Paralithoxus planquettei was assessed by the IUCN Red List as Least Concern on 19 October 2020. It is Not Evaluated under CITES and CMS, and is harmless to humans. Its relatively wide distribution across the coastal drainages of French Guiana and its apparent tolerance of marginal, seasonally drying habitats underpin the Least Concern listing. As with other forest-stream fishes of the Guianas, localised threats from deforestation and watershed disturbance could affect populations, but the species is not presently considered threatened.