Otocinclus mimulus Axenrot & Kullander 2003

Presence of an iris diverticulum; elevated, enlarged odontodes at posterior supraoccipital tip; lateral series 24-25; lateral line canals only on first 4-6 anterior plates in median series; lateral trunk coloration variable, including either row of 4-6 distinct dark blotches or distinct dark stripe extending from pterotic posterior process to base of caudal fin, or diffuse mixture of those two color patterns; premaxillary teeth 14-18 (commonly 15-16); mandibular teeth 12-16 (commonly 14); caudal vertebrae 15-17, modally 17; triangular pigment mark at anterior dorsal- fin base occasionally faint or absent (Ref. 52874).

Vertebrae: 22 - 23

Found in stream with dark, slightly turbid water, flowing through a landscape of mixed low forest and pasture (Ref. 52874). Collected at the margin of an open field, but the stream flowed through dense low forest left along its bank and providing shadow (Ref. 52874). Usually occurs in areas with sandy bottom, bank vegetation entering water or with marginal aquatic plants, dark, clear or slightly turbid water and limited associated fauna (Ref. 52874). Mimics Corydoras diphyes (Ref. 52874). Mimicry is unusual because the two species occupy different microhabitats and it is hypothesized to operate with a primarily visual predator moving between the microhabitats, tentatively identified as the cichlid Crenicichla lepidota (Ref. 52874).

Otocinclus mimulus is a species of armoured catfish found in small tributaries of the Monday river, itself a tributary of the Paraná river.

Otocinclus mimulus is a Batesian mimic of Corydoras diphyes. C. diphyes is inedible to many species due to its bony armor and so individual O. mimulus that look more similar to C. diphyes are less likely to be eaten by predators like Crenicichla lepidota. O. mimulus is named for its mimicry of C. diphyes.