I’ve seen a couple of documentaries recently that mention Ocean Sunfish, seriously huge fish prone to parasitic infection. They deal with this by going to special cleaning stations where smaller fish pick the parasites off. So ordered is this behaviour that the sunfish line up and wait their turn for a cleaning. As impressive as that is, I’ve just learned that if they have a particularly irksome parasite they’ll swim to the surface and find a seagull that can use its beak to dig out the problem. I just love evolution.