Remora fish attaching to sharks for food and transport shows:
A remora gains transportation and access to food by attaching to a shark with a modified dorsal-fin suction disc. It may consume scraps from the shark’s meals and exploit feeding opportunities encountered during travel. In the traditional interpretation, the remora benefits while the shark experiences little measurable effect, giving the (+, 0) sign pattern of commensalism. The remora does not normally extract host tissue like a parasite, and reciprocal benefit is not required as in mutualism. Some remoras remove ectoparasites or clean wounds, which could benefit the shark and shift particular
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 8-13
