Up: Portunus trituberculatus - http://en.wikipedia.org/wiki/Portunus_trituberculatus
Portunus trituberculatis is a type of blue crab found of the coast of southeast asia. This crab's immune system can be altered through the use of ammonia content added into its environment. When 1 - 20 mg of ammonia is added to the environment, phagocytosis begins to slowdown. Not only that, but the anti-bacterial resistances begin to slow down, meaning that the animal becomes weaker towards viruses. These conditions are only temporary, however, as they will only last for twelve hours before they go through homeostasis.