Published on 05:15 PM, June 09, 2016

Humans are just starting to understand the octopus — and it's mind-blowing

A male octopus will sometimes send a gift along with his package — one of his eight arms, which he severs himself. Photo taken from Business Insider.

Today is the World Oceans Day!

Every year on June 8, people around the world celebrate this day, and to join in on the fun here are some mind-blowing facts about octopuses, according to a report published in the Business Insider.

With their eight arms and giant egg-shaped head, octopuses are one of the most alien-looking creatures on the planet.

Yet scientists have an extremely difficult time studying them in the wild because these highly intelligent invertebrates are the ultimate masters of disguise.

In her book, "Octopus!" Katherine Harmon Courage travels the globe to swim, observe, and even taste some of the many octopuses of the world. Here are 8 mind-blowing facts she learned about this squishy predator of the sea along her epic journey.

Octopuses have three hearts. The main heart will actually stop beating when the animal is swimming, so it can't swim very far before tiring out. Photo from business insider.
When they do bleed, octopuses bleed blue blood, not red. That's because their blood is high in copper instead of iron. Photo: Business Insider
Over 95% of all animals on Earth are invertebrates. The octopus is the smartest of them all and has approximately 300 million neurons throughout its body. That's not much compared to the 100 billion in humans, but it's a giant leap from the 16 million in frogs. Photo: Business Insider