I just can’t resist telling you guys about parasites that alter host behavior. Today, the hosts are zombie crabs, and the parasite is the Sacculina barnacle.
The larval female barnacle finds a crab and infects it. They specifically take up residence on the crab abdomen, where the crab would carry its own eggs (if it were female). The barnacle will infect male and female crabs, and if it infects a male, the male’s hormones will be manipulated so that the male’s morphology and behavior are altered to be more like female morphology and behavior. NEAT!
Later, larval male barnacles come fertilize the female’s eggs. The host crab will then care for the parasite eggs!!
I highly recommend doing some googling for photos/videos.