Arinosaster patriciae gen. nov. et sp. nov. A Rio Claro stream, close to the sinkhole; B Rio Claro stream at the resurgence from the sinkhole C Rio Claro at the entrance of the underwater cave showing the moment scuba divers are getting into the sinkhole D Colonies of Arinosaster patriciae gen. nov. et sp. nov. encrusted in crevices of the sinkhole rocky walls. Fish seen in D pertain to the species Leporinus octomaculatus Britski & Garavello, 1993. Photos A–C by Alexandre Cunha Ribeiro. Photo D by Patricia Arrais Rodrigues da Silva.