The Zebra Otocinclus is probably the most spectacular and most attractive Otocinclus species for the aquarium hobby. It has been known for some time that there are two forms of the species described in 2004 as O. cocama: one from the lower Río Ucayali and another one from the Río Tigre. Both rivers are tributaries to the Río Marañón, which ultimately flows into the Amazon. While the Ucayali form, on which the description is based, has been exported for the aquarium trade since around the turn of the millennium, it is mainly the Tigre form that has been on the market in recent years, at least in Germany. Both populations can be clearly distinguished by their stripe pattern. The question of whether the populations can also be distinguished morphologically and genetically, and thus also whether they are merely variants of one species or two distinct species, was investigated by Eduardo MEJIA and Roberto E. REIS and recently published. Continue reading →