Taxonomy & naming
Loricariichthys microdon was formally described by Carl H. Eigenmann in 1909 in the Annals of the Carnegie Museum (volume 6, number 1, page 7), from specimens collected in the Rupununi River, Guyana. The original combination was Loricaria microdon, later transferred to the genus Loricariichthys, and the Catalog of Fishes (Eschmeyer, CAS) recognises Loricariichthys microdon (Eigenmann, 1909) as the valid name.
The genus Loricariichthys belongs to the subfamily Loricariinae — the true whiptails — characterised by greatly elongated, depressed bodies, long filamentous tails, and the diagnostic lip-brooding reproductive strategy of males. The species epithet microdon is formed from the Greek mikros (small) and odon/odous (tooth), referring to the relatively small dentition.
Morphology
Adults reach up to 7 in standard length (SL) based on FishBase (reference 137577). The body is strongly depressed and covered in the interlocking bony scutes typical of loricariids, tapering into the characteristic elongated caudal filament of the Loricariinae. Colouration is generally brownish and cryptic, matching the sandy and detrital substrates the species inhabits.
The most striking anatomical feature is the hypertrophied lower lip in breeding males, which becomes greatly expanded and fleshy — forming the brooding pad used to carry the egg mass. This adaptation is shared across the genus Loricariichthys and represents one of the most unusual parental care strategies within Loricariidae. Outside the breeding season, male and female lip morphology is more similar, though experienced keepers note that male lower lips tend to retain a fuller appearance.
Habitat
Loricariichthys microdon is known from the Rupununi River basin of Guyana, part of the broader Essequibo River system and the Coastal Rivers of the Guianas. The Rupununi is a seasonally flooded savanna river, with water levels rising dramatically during the wet season and exposing extensive shallow floodplains. Water conditions in these systems are generally warm and soft to moderately hard, with low to moderate conductivity.
Like other loricariin whiptails, L. microdon is a demersal species, spending the majority of its time resting on or moving across the substrate. Sandy, silty, and detritus-rich bottom substrates are preferred. The genus is also reported to be a facultative air-breather — capable of taking atmospheric oxygen when dissolved oxygen levels in the water drop, a useful adaptation in the seasonally stagnant backwaters of its range.
Feeding
Loricariichthys microdon is an omnivorous detritivore with a trophic level of approximately 2.6. In common with other members of the genus, the diet encompasses varied detritus, fine sediments, algal material, microcrustaceans, fungal matter, plant remains, and larval insects gleaned from the substrate. The ventrally positioned mouth and flat body posture are adaptations for efficiently grazing and sifting food from bottom sediments.
In aquarium conditions, the species should be offered sinking foods — algae wafers, spirulina tablets, and blanched vegetables — supplemented with fine frozen foods such as cyclops or daphnia. A soft, fine substrate allows the fish to express natural foraging behaviour.
Mating
Breeding behaviour in Loricariichthys microdon has not been documented in captivity in published accounts, but the reproductive biology of the genus is well characterised from related species and aquarium observation of congeners. Males develop the greatly expanded, pad-like lower lip that functions as the brooding surface. Courtship presumably involves the male establishing a territory on the substrate and attracting females to spawn. The eggs are fertilised and then pressed against the male's enlarged lower lip, where they are retained throughout incubation.
Breeding
Loricariichthys microdon is a lip-brooder — one of the most unusual reproductive modes documented within Loricariidae. After spawning, the male presses the fertilised egg mass against his greatly expanded lower lip, holding the clutch in place by pressing the lip flat against the substrate or a hard surface. He carries the eggs in this manner until they hatch, ventilating them through gentle movements. This strategy, shared by males throughout the genus Loricariichthys, contrasts with the cave-spawning and substrate-guarding seen in many other loricariids.
No specific captive breeding reports for L. microdon are available in the literature. Water chemistry parameters mimicking the soft, warm conditions of the Rupununi system, combined with a fine sandy substrate, would represent a reasonable starting point for conditioning attempts.
In the aquarium
Loricariichthys microdon is rarely encountered in the aquarium trade and is primarily of interest to specialist loricariid keepers attracted by the extraordinary lip-brooding behaviour of the genus. The species reaches approximately 7 in SL, placing it in the medium-large category among whiptail plecos, and requires an aquarium of at least 47 in length with generous open substrate area.
A soft, fine sandy substrate is strongly preferred — sharp gravel risks abrasion on the ventral surface. The aquarium should be furnished with driftwood, leaf litter, and areas of open sand that mimic the natural Rupununi environment. Water conditions should be warm (75–82 °F), soft to moderately hard, and slightly acidic to neutral. Good filtration and gentle flow are advisable; stagnant conditions are not suitable.
The species is peaceable toward dissimilar tankmates but may be territorial toward conspecifics or other bottom-dwelling loricariids competing for substrate space. It is best kept singly or as a pair with ample space.
Conservation
The IUCN Red List assessed Loricariichthys microdon as Least Concern in January 2021, with a range centred on the Rupununi River basin within the Essequibo system of Guyana. No major threats to the population have been identified. The Rupununi drainage remains relatively pristine compared to heavily developed river systems elsewhere in South America, supporting a diverse fish fauna.
The species is not a significant target of the ornamental fish trade and is collected infrequently. No captive breeding programme is known. General pressures on Guyanese river systems — including artisanal gold mining, which causes sedimentation and mercury contamination in some drainages — are worth monitoring, but at present L. microdon is not considered at risk.