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YouTube - amazing mantis shrimp video
It's a Mantis Shrimp. There are many different kinds with some amazing and cool color schemes, perfect inspiration for a Tyranid theme. They are the perfect predator with the most complex eyes in the animal kingdom. Super cool (unless they sneak into your reef aquarium. They will kill most everything and are very difficult to catch).
Wow, that's crazy! Definitely a Tyranid vanguard organism. We must prepare... Anti-Tyranid militia, MOBILIZE!