Taxonomy & naming
Loricaria luciae was formally described by Thomas, Rodriguez, Carvallaro, Froehlich & Macedo Corrêa e Castro in 2013, published in Zootaxa 3745(3): 358–378 (accepted 11 November 2013, published 5 December 2013). The Catalog of Fishes (Eschmeyer, CAS) treats this as a valid species. The type locality is the left bank of the río Paraná, at a private park (Club San Martin) near the town of Perichon, north of Route 12, northeast of Corrientes city, Corrientes Province, Argentina; GPS coordinates approximately 27°25'6.94"S, 58°45'27.47"W.
The genus Loricaria, type genus of the family Loricariidae and the subfamily Loricariinae, contains thirteen accepted species as of the original description date. L. luciae is diagnosed within the genus principally by the combination of: (1) a pectoral girdle entirely naked or bearing only small isolated plates near the pectoral fin base; (2) large, tightly joined abdominal plates confined to the median space between the lateral abdominal plate rows; (3) 32–33 total lateral plates (modally 32); and (4) a large post-ural plate at the caudal-fin base (17.0–20.3% head length). This plate arrangement distinguishes it from the closely related L. coximensis, with which it is sympatric in parts of the Paraguay drainage.
GBIF lists the species at species ID 8323610 with full taxonomic attribution to Thomas et al. 2013.
Morphology
Adults reach 7.5 in standard length (SL) — FishBase records this as the maximum for the species, based on male or unsexed specimens. Aquarium Glaser sources note adults in the range 5–7.5 in SL, confirming L. luciae is larger than the closely related L. coximensis. The body plan is the classic depressed, elongate Loricaria profile: a broad, flat head with a large iris operculum (a mobile iris flap that regulates light entry to the eye), a widened snout, and a progressively narrowing caudal peduncle.
The pectoral girdle is completely naked — unplated — or carries only small isolated plates close to the pectoral fin insertion. This nakedness of the cleithrum region is a primary diagnostic character. The lateral abdominal plate rows are shorter and the central abdominal plates broader than in L. coximensis, contributing to the distinctive ventral plate geometry.
Sexual dimorphism is prominent and unusual: males display orange-coloured teeth along the front sides of the head. This orange dentition, visible when the fish opens its mouth, is a sexually dimorphic character not matched in females of the species. As in other Loricaria, males are also expected to develop odontodes on the snout and pectoral region during breeding condition, though the orange teeth represent the most striking external dimorphism.
Habitat
Loricaria luciae is distributed throughout the río Paraguay basin of Bolivia, Brazil, and Paraguay, extending south to the confluence of the río Paraguay with the río Paraná, and continuing into Argentinian stretches of the Paraná drainage — the type locality in Corrientes Province, Argentina confirms its presence into the lower Paraná system.
The original description documents occurrence across a range of habitat types: from small, seasonally intermittent streams carrying clear water to large, turbid rivers with sand and mud substrates. This breadth of tolerance is consistent with the Paraguay-Paraná floodplain system, which transitions seasonally between high-water inundation and low-water concentration of fish into main channels. L. luciae is syntopic in parts of its range with L. apeltogaster, L. coximensis, and L. simillima.
No specific water chemistry parameters are available in the sources; the Paraguay-Paraná basin in this reach typically carries warm, moderately productive water with neutral to slightly alkaline pH and moderate hardness in the main channels, with softer, clearer conditions in tributary streams.
Feeding
Loricaria species are benthic detritivores and biofilm grazers. The ventral mouth, positioned flat against the substrate, rasps biofilm — diatoms, bacteria, algae, fungal hyphae — from the surfaces of sand, mud, rock, and submerged wood. Fine detritus ingested with substrate material also contributes to the diet. The large, flat mouth and depressed body allow the fish to maintain contact with the substrate surface across a wide area.
In the aquarium, sinking foods are essential: algae wafers, spirulina tablets, and blanched vegetables (courgette/zucchini, cucumber, spinach) are appropriate. Supplement periodically with small live or frozen invertebrates — bloodworm, Daphnia. Access to a sand or fine-gravel substrate and flat wood or stone surfaces is beneficial. Avoid coarse substrate that can abrade the ventral surface.
Mating
The Loricaria reproductive system involves mouthbrooding by the male — a striking departure from the substrate-spawning and cave-guarding seen in most other loricariid genera, including the closely related Rineloricaria. In Loricaria, the male collects the egg mass into his mouth after spawning and broods it there until hatching.
Sexual dimorphism in L. luciae includes the notable orange dentition of males — teeth along the front sides of the head that are strikingly coloured compared to females. This character, visible when the fish is relaxed or feeding, presumably plays a role in conspecific recognition or mate assessment, though the precise behavioural function has not been documented in the published literature for this species.
As the male approaches spawning readiness, care similar to other whiptail genera applies: conditioning on varied diet, provision of a suitable spawning site, and appropriate water conditions consistent with the Paraguay-Paraná origin.
Breeding
Loricaria luciae belongs to a genus in which males brood the egg mass in the mouth — a mouthbrooding strategy that distinguishes Loricaria from the substrate-guarding Rineloricaria and from the cave-spawning Ancistrus and Panaqolus. After the female deposits eggs, the male takes the egg mass into his buccal cavity and retains it throughout incubation, periodically aerating the eggs by manipulating them in the mouth.
Aquarium records indicate that L. luciae can be kept and bred in captivity; care is described as similar to the better-known L. simillima. Successful breeding requires conditioning adults on a varied diet, maintaining clean water, and providing appropriate substrate for spawning — a flat, open sandy area is more appropriate than a closed cave, since Loricaria does not require a cavity in the manner of cave-spawning loricariids.
Post-hatch, fry emerge from the male's mouth as miniature adults and begin grazing almost immediately. The male does not continue active care once fry are free-swimming.
In the aquarium
Loricaria luciae is a large whiptail — adults to approximately 7.5 in SL — and requires a correspondingly spacious aquarium. A tank of at least 30 US gal with a long footprint is suitable for a single specimen or a pair; a group requires proportionally more space. The most critical requirement is substrate: fine, smooth sand is ideal, both for the benthic lifestyle and to protect the unplated ventral surface and delicate mouth structures.
Water parameters should reflect the Paraguay-Paraná origin: temperature in the range of 72–82 °F, pH neutral to slightly alkaline (6.8–7.8 is reasonable), and moderate hardness. The species occurs in both clear-water streams and large turbid rivers in the wild, suggesting reasonable flexibility in water chemistry within this range. Good filtration and regular water changes are important; sedimented substrate can stress a benthic fish that relies on clean bottom conditions.
Decor should include flat wood and smooth stones for resting and grazing. Dense planting is not necessary and may conflict with the open sandy areas the fish prefers. The species is peaceful and can be kept with other large, non-aggressive fish appropriate to the Paraguay-Paraná biotope — larger tetras, peaceful South American cichlids at the smaller end of the size spectrum, and other loricariids if the tank is large enough to accommodate multiple territories.
The orange teeth of the male provide an attractive and unusual visual feature; careful observation of feeding behaviour will reveal this dimorphism in a conditioned adult male.
Conservation
The IUCN Red List assessed Loricaria luciae as Least Concern in 2020. The species has a broad distribution across the Paraguay-Paraná system, occurring in Bolivia, Brazil, Paraguay, and Argentina, and tolerates a range of habitat types from small streams to large rivers. This breadth of distribution and apparent habitat flexibility underpin the Least Concern rating.
The Paraguay-Paraná basin faces ongoing pressures including agricultural expansion and associated sedimentation, wetland drainage affecting the Pantanal and adjacent areas, and hydrological modification through river channelisation and dam construction in upper tributaries. For a benthic, substrate-dependent species, changes in sediment load and substrate character in main channels can affect feeding and spawning success. At present, however, no evidence of population decline has been documented for L. luciae, and the species is not targeted by commercial fisheries.