Sea anemones and hermit crabs
Sea anemones (Calliactus spp) hitchhike on the back of hermit crabs, scoring a ride across the seabed and extending their tentacles to eat the crab’s leftovers. Crabs actively recruit these passengers. After poking an anemone with its pincers – causing it to release its grip from its current home – the crab holds it in place so the anemone can reattach to the crab’s own shell.