Howard Fischer Uppsala, Sweden   Lateral view of the candiru Paracanthopoma sp. in field aquarium. From Jansen Zuanon and Ivan Sazima, “Free meals on long-distance cruisers: the vampire fish rides giant catfishes in the Amazon,” Biota Neotropica 5, no. 1 (2005), via ResearchGate. CC BY-NC 4.0. “[N]o one has stepped forward to observe the candiru’s life…