Otocinclus is a genus of catfish in the family Loricariidae native to South America, commonly known as "dwarf suckers" or "otos". This genus, like other loricariids, is characterized by rows of armour plating covering the body, as well as the underslung suckermouth. They are generally small in size; O. tapirape is the smallest of the species (2.4 cm), while O. flexilis is the biggest (5.5 cm). These species have adaptations that allow them to breathe air. A duct forms at the junction between the esophagus and the stomach and expands into an enlarged, ring-like diverticulum, characteristic of this genus, which allows air-breathing. Otocinclus are popular aquarium fish, and they are often purchased as algae eaters. It is difficult to breed them in captivity, and only wild caught Otocinclus are available to hobbyists. This genus is widely distributed east of the Andes of South America, throughout the lowlands from northern Venezuela to northern Argentina, but are generally absent from the Amazon and the Orinoco lowlands. Etymology The Otocinclus name is derived from the Greek oto, meaning ear and the Latin cinclus, meaning a latticework, an allusion to the holes in the head in the region of the ear. Taxonomy Otocinclus is the most basal genus of the tribe Hypoptopomatini of the subfamily Hypoptopomatinae. However, phylogenetic relationships are currently under study and this genus may eventually be relocated. Its monophyly is supported by seven derived features. O. batmani, O. bororo, O cocama, O. huaorani, O. mariae and O. mura form a monophyletic group within this genus. A monophyletic group is also formed by O. flexilis, O. mimulus and O. xakriaba, which all share mimicry as a synapomorphy. Species There are currently 19 recognized species in this genus: Otocinclus arnoldi Regan, 1909 Otocinclus batmani Lehmann A., 2006 Otocinclus bororo Schaefer, 1997 Otocinclus caxarari Schaefer, 1997 Otocinclus cocama R. E. dos Reis, 2004 Otocinclus flexilis Cope, 1894 Otocinclus hasemani Steindachner, 1915 Otocinclus hoppei A. Miranda-Ribeiro, 1939 Otocinclus huaorani Schaefer, 1997 Otocinclus juruenae A. C. Ribeiro & Lehmann A., 2016 Otocinclus macrospilus C. H. Eigenmann & W. R. Allen, 1942 Otocinclus mangaba Lehmann A., Mayer & R. E. dos Reis, 2010 Otocinclus mariae Fowler, 1940 Otocinclus mimulus Axenrot & S. O. Kullander, 2003 Otocinclus mura Schaefer, 1997 Otocinclus tapirape M. R. Britto & C. L. R. Moreira, 2002 Otocinclus vestitus Cope, 1872 Otocinclus vittatus Regan, 1904 Otocinclus xakriaba Schaefer, 1997 Macrotocinclus affinus was considered to