A crab with blue coloration

Okinawa Nature Photography, Flickr

The toxic reef crab (also known as the devil reef crab) is aptly named. This crab's muscles store two of the most lethal toxins— tetrodotoxin and saxitoxin. These gorgeous crabs are easy on the eyes but be sure to avoid them on the dinner plate. Eating a crab will kill the diner in a matter of hours.