Taxonomy & naming
Otothyropsis marapoama was described by Ribeiro, Carvalho, and Melo in 2005 in Neotropical Ichthyology (3(4): 489–498) as both a new genus and a new species; it is the type species of Otothyropsis. The Catalog of Fishes (Eschmeyer, CAS) recognises Otothyropsis marapoama Ribeiro, Carvalho & Melo, 2005 as valid.
The genus belongs to the subfamily Hypoptopomatinae, the dwarf suckermouth catfishes — small loricariids well known in the hobby through relatives such as Otocinclus. The specific epithet derives from the municipality of Marapoama in São Paulo State, near the type material.
Morphology
Otothyropsis marapoama is a very small loricariid, reaching a maximum recorded standard length of about 1.5 in. It shows the compact, dorsoventrally flattened build and plated armour characteristic of the Hypoptopomatinae, together with the ventral suckermouth used to adhere to surfaces.
The characters distinguishing the genus and species are detailed in the original description (Ribeiro et al., 2005). Sexual dimorphism is not described in the sources available here.
Habitat
The species is known from the rio Tietê basin in southeastern Brazil. It is a freshwater, demersal, tropical fish with a reported trophic level of approximately 2.3, consistent with a low-on-the-food-chain grazing habit.
Detailed in-situ water parameters are not published in the sources consulted. Small hypoptopomatines of this region typically occur in clear, shallow streams and marginal vegetation, clinging to plant stems, leaf litter, and submerged surfaces.
Feeding
No feeding study specific to Otothyropsis marapoama is available, but its reported trophic level near 2.3 indicates a herbivore–detritivore diet. Like other dwarf suckermouth catfishes, it is expected to graze on aufwuchs — the film of algae, diatoms, and microfauna coating submerged surfaces. This is an inference from the genus and trophic data, not a documented observation; no captive feeding data exists.
Mating
No information on courtship or mating behaviour has been published for this species.
Breeding
No breeding report exists for Otothyropsis marapoama. Reproduction in the wild and in captivity is undocumented in the sources consulted.
In the aquarium
Otothyropsis marapoama is not present in the ornamental trade in any established way, and no husbandry data has been published. By analogy with other dwarf hypoptopomatines, such a fish would presumably need a mature, well-planted tank with stable, clean water and ample grazing surfaces, since these tiny algae-grazers are sensitive to poor water quality and depend on biofilm. This is general guidance for the group, not tested advice for this species.
Conservation
The IUCN Red List assessed Otothyropsis marapoama as Least Concern (assessed 7 November 2018). The rio Tietê basin is heavily impacted by urbanisation and pollution around São Paulo, but the assessment does not currently rank the species as threatened. Small-range stream fishes of this kind nevertheless remain vulnerable to localised habitat degradation and water-quality decline.