Lasiancistrus is a genus of suckermouth armored catfishes. They are native to South America and Panama.
Lasiancistrus was first described as a subgenus of Ancistrus in 1904, including A. heteracanthus, A. pictus, A. mystacinus, and A. guacharote. Later, it was raised to genus level, and several unrelated species were included. Many of these species have since been moved to other genera, such as Pseudolithoxus.[1] Most Lasiancistrus species had been described from few specimens; the genus was revised in 2005, synonymizing many of the existing species into four species, L. caucanus, L. guacharote, L. heteracanthus, and L. schomburgkii. L. maracaiboensis and L. mystacinus are synonyms of L. guacharote. L. castelnaui, L. caquetae, L. guapore, L. multispinis, L. pictus, and L. scolymus are synonyms of L. schomburgkii. L. planiceps, L. mayoloi, and L. volcanensis are synonyms of L. caucanus. In addition, two new species, L. saetiger and L. tentaculatus, were described.[1]
Unlike many other members of Ancistrini, the ranges of most of the Lasiancistrus species are quite broad. Lasiancistrus species are found throughout the Amazon basin, the upper and middle of the Orinoco River basin, the Rupununi River basin (Essequibo River drainage), the Lake Maracaibo drainage, and drainages west of the Andes in Colombia and Panama to the Bayano River.[1]
The species of Lasiancistrus are most commonly found in small creeks, typically in swift flow. However, some of the streams where Lasiancistrus can be found are in the lowlands, and hypoxia has been observed in one such stream, suggesting that lowlands are not a barrier to the movement of these species. Lasiancistrus are most common in lower piedmont streams and are more likely to spread between rivers this way rather than through the lowlands.[1]
Adult Lasiancistrus have whiskerlike odontodes on their cheeks which are unique among the Loricariidae. These hair-like odontodes are part of their evertible cheek odontodes; they are very narrow, but appear to be made out of the same material as the other odontodes.[1] Their presence does not appear to be sexually dimorphic, although males may have longer ones.[1] In nuptial males, there are fleshy tentacles on the pectoral-fin spines longer than their associated odontodes, which differentiates it from all genera except Ancistrus. They are differentiated from Ancistrus by the presence of plates along the edge of the snout (Ancistrus lack these plates) and by maximally having translucent tentacles on the snout that have odontodes associated with them (in Ancistrus there are larger tentacles without associated odontodes coloured the same as the head).[1]
The snout of nuptial males are almost square, rather than rounded as in females and juveniles. Adult males of most species (except L. tentaculatus) have whiskerlike odontodes at anterolateral corner of snout; in L. tentaculatus, males have tentacles instead of whiskerlike odontodes along anterior margin of snout. Also, nuptial males with tentacles longer than their associated odontodes on the pectoral-fin spine.[1]