Unfortunately, the “Giant Otos” of the genus Oxyropsis are rarely offered for sale. Three species are currently scientifically accepted, O. carinata and O. wrightiana, which inhabit the upper and middle Amazon basin, and O. acutirostris from the upper Orinoco and Rio Negro basin.
Oxyropsis can be distinguished from the similar species of the genus Hypoptopoma by the strongly flattened caudal peduncle with a keel on the side. Otherwise they look very similar; it seems that one Hypoptopoma species and one Oxyropsis species occur side by side in nature, which apparently differ in details of their ecology.
From Brazil we have now received Oxyropsis (together with Hypoptopoma psilogaster) from the Rio Purus, which are probably O. acutirostris. The three species hardly differ in body coloration. The animals from the Purus differ from Oxyropsis from Peru, which we were able to import in 2020 and at the time referred to as O. carinata, in the coloration of their caudal fins. In the Purus fish there is only a large dark spot in the lower half of the caudal fin, whereas in the animals from Peru a dark band runs through the fin over the entire height of the fin behind the root of the tail. O. acutirostris in the last revision of the genus (Aquino & Schaefer 2002: 384, Fig. 7) also shows the aforementioned caudal fin coloration of the Purus animals, which is ultimately the main reason for our determination.
Oxyropsis acutirostris grows to a length of 4-6 cm and is a very peaceful fish. The dentition indicates that this species mainly feeds on Aufwuchs. As details on the aquarium biology of Oxyropsis are generally not yet known, a water temperature of 24-28°C is recommended, as has proved to be the case for many fish in the Rio Purus. The chemical composition of the water is otherwise rather unimportant for maintenance, just avoid extremes. A pH value between 6.5 and 7.5 in soft to medium-hard water is certainly not wrong, but only time will tell whether other parameters are required for breeding.
For our customers: the fish have code 274227 on our stock list. Please note that we only supply the wholesale trade.
Literature:
Aquino, A. E. and S. A. Schaefer (2002): Revision of Oxyropsis Eigenmann and Eigenmann, 1889 (Siluriformes, Loricariidae). Copeia 2002 (no. 2): 374-390.
Text & photos: FRank Schäfer
