Loricariichthys acutus is a species of freshwater ray-finned fish belonging to the family Loricariidae, the suckermouth armored catfishes, and the subfamily Loricariinae, the mailed catfishes. This catfish has a wide distribution in the Amazon basin of Bolivia, Brazuil, Colombia and Peru, the upper Paraguay River basin in Bolivia and Brazil and the Essequibo River in Guyana. L. acutus reaches a maximum standard length of , a maximum weight of and is thought to be a facultative air breather.
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