If sea sponges were to launch a PR campaign, their slogan might be “we are not plants!”
While they don’t have eyes, ears, mouths, hearts or brains, sponges are multicellular, lack cell walls and have the ability to produce sperm cells — all characteristics of animals.
There are over 6,000 species of them, all of which are found in saltwater, and they can measure up to 11 feet. And yes, you’ve read that right — some massive species of them are estimated to live for more than 2,300 years.
Sponges cleverly use their holes to filter water and store nutrients. Their bodies consist of multiple layers held together by a jelly-like substance called mesohyl, and they can regenerate if broken apart.
Though humans have used sponges to bathe, clean and medicate (they’re an excellent source of iodine), most other sea creatures leave them be.