Cat-eLog Right Loricariidae Right Hypoptopomatinae Right Otocinclus

Down Cat-eLog Data Sheet
Scientific Name Otocinclus flexilis  Cope, 1894
Common Names Peppered Oto
Argentinischer Ohrgitter-Harnischwels (Germany)
Type Locality Rio Jacuhy [Jacuí], Rio Grande do Sul, Brazil.
Synonym(s) Macrotocinclus flexilis, Otocinclus fimbriatus
Pronunciation auto SINK luss - flex ill iss
Etymology Greek, ous, oto = ear + Latin, cinclus = latticework; in allusion to the holes of the head in the ears. 
Article Link - CotM Right 2009 Right May
Down Species Information
Size 55mm or 2.2" SL. Find near, nearer or same sized spp.
Identification An easy species of Otocinclus to identify although two colour forms exist. One with a more pronouced darker and lighter "peppering" and one with a more regular pattern. This variance aside, the colouration is the same as the common peppered Cory, Corydoras paleatus. Coloration of individual otos vary with mood. Normal coloration is beige with spots, but this species (in presumed breeding mode) turn darker, and may become almost black.

Other species of Otocinclus which can have a blotched color pattern are O. arnoldi, O. mimulus, and O. xakriaba. O. flexilis is distinguished from O. arnoldi and O. mimulus by having six branched pectoral-fin rays (vs. five branched rays in O. arnoldi and O. mimulus). O. flexilis is distinguished from O. xakriaba by the presence of a triangular pigment mark at the dorsal-fin base of O. flexilis (absent on O. xakriaba).
Sexing Females are considerably larger than males and fuller in girth.
Down Habitat Information
Distribution South America: Middle and lower Paraná/Paraguay, Uruguay and La Plata basins and Atlantic coastal streams of southeastern Brazil.
La Plata, Uruguay (click on these areas to find other species found there)
La Plata, Paraná, Middle Paraná (click on these areas to find other species found there)
La Plata, Paraná, Lower Paraná (click on these areas to find other species found there)
La Plata, Paraná, Paraguay (click on these areas to find other species found there)
La Plata (click on these areas to find other species found there)

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IUCN Red List Category Least Concern, range map and more is available on the IUCN species page. Last assessed 2018.
pH 6.5 - 7.8
Temperature 20.0-25.0°C or 68-77°F (Show species within this range)
Other Parameters 2-25 dGH.
Down Husbandry Information
Feeding New imports can be tricky to acclimatize to prepared foods, but once this hurdle is overcome (using frozen bloodworm and algae wafers) they feed greedily.
Furniture Less reliant on plants than other Otocinclus species, nevertheless, tall leaved plants like Vallisneria provide habitat and shade for these species that also appreciate vertical wood surfaces but generally move around the aquarium without preference. Gravel or sand may be used.
Compatibility A highly social, diurnal and hardy species. Slightly aggressive (more akin to slightly larger loricariids); they defend food albiet half-heartedly, and dominate Corydoras at feeding time but not to the other species detriment.

Also when kept with Corydoras paleatus, the Corys appear fooled by the oto mimics, and often follow them around, gulp air at the same time the otos do, and even male corys display to otos. The otos on the other hand seem aware which fish are conspecifics, as they're noticeably more aggressive towards the corys than to each other. Perhaps the bright white opercular diverticulum serves as a recognition signal for the otos? They have a curious behaviour that they nibble at each other and corys at the base of the dorsal fin, something which is apparently very unpleasant for the receiving fish - it looks like aggressive/dominance behaviour.
Suggested Tankmates Keep in groups (preferably at least six) with any small to mid-sized community fish.
Breeding It is reported that smaller male fish 'dance' in front of larger fish, 'nudge' the larger fish in the region of the cloaca, and also follow them around very closely. Actual reproduction is unreported.
Breeding Reports There is no breeding report.
Down Further Information
Reference Proceedings of the American Philosophical Society v. 33, pp 97, Pl. 8 [7] (figs. 13, 13a-b).
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Last Update 2020 Sep 20 01:45 (species record created: 2004 Aug 21 00:00)