50 Baby Animals That Are So Cute, Your Brain Might Not Comprehend How It’s Possible

You might know that the biggest animal on earth is the blue whale. But what do you think the tiniest is? Maybe an ant? Or a flea? Apparently, it's neither of those. According to experts, the world's most minute creatures are myxozoans.

"All of us at some point in our life cycle have tiny stages, but when we're mature, we're complex multicellular animals," explains Beth Okamura, a professor at the Natural History Museum in London. "That's not the case for Myxozoa. When they mature, they're still single cells."

According to the University of Hawaii, myxozoans can be up to 100 times smaller than a grain of sand. Or as small as 0.02 millimeters (20 micrometers) across as adults.

And if you're wondering what exactly they are, Science Direct defines them as aquatic parasitic animals, adding that they were probably derived from jellyfish.

"With 2,402 species described, many have a two-host lifecycle, involving a fish and an annelid worm or bryozoan," reads the site. "For example, Ceratomyxa shasta is a virulent myxosporean parasite of salmon and trout in the Pacific Northwest."

Okamura says that most myxozoan species produce infectious waterborne spores. "Cells from these spores invade and develop inside both vertebrate hosts, such as fish, and invertebrate hosts, like annelid worms," explains the expert.

Some myxozoans infect the gallbladders of Amazon fish and "grow" into worm-like creatures with unicellular bodies, adds the sciencedirect.com site. A few can cause diseases in their hosts, but mostly these tiny animals are harmless.

In terms of mammals, the prize for the tiniest apparently goes to both the Etruscan shrews and bumblebee bats. Bumblebee bats grow to a length of around 1.1 to 1.3 inches and have a wingspan of around 6 inches, while the shrews can reach a mighty 2 inches long.