3While the blue-ringed octopus is only about the size of a golf ball and its glowing rings are pretty, it's also one of the deadliest animals on the planet. Blue-ringed octopuses flash their blue rings when danger occurs, and they're armed with a powerful toxin--tetrodotoxin. These critters are unique in that they are both venomous and poisonous! Readers get the chance to see these amazing animals up close without worrying about being bitten. The text is packed with fascinating facts about these fearsome marine creatures and addresses numerous topics essential to the elementary science curriculum.