If you've ever donated blood, you understand what an incredibly important act it is! After all, a blood transfusion occurs every two seconds in the U.S. — roughly half the time that it's taken to read this sentence.
We know what a critical act it is too, and we encourage you to schedule your next donation today if you can! But let's just say you have some time between giving blood and are looking to have some not-totally-serious questions answered: we've got you covered there, too!
Last spring, we tackled one such question: Can mosquitoes tell our blood types? Turns out that a) mosquitoes can sense a lot more than what's in our blood and b) our post generated lots of interest!
MORE: Why Am I Mosquito Magnet?
No wonder, then, that we're back to answer another question that's been bugging us:
Do Bugs Have Blood?
Believe it or not, insects don't technically have "blood," at least not in the red-colored, oxygen-rich way we're accustomed to. Instead, they circulate a unique fluid called hemolymph that is often clear or yellowish and doesn't contain hemoglobin and red blood cells.
Insects have an open circulatory system, which allows hemolymph to flow freely, bathing their organs while keeping their tiny bodies nourished. Of course, no red blood cells means insects need another pathway for oxygen delivery: unlike us, oxygen travels through a network of tiny tubes called a tracheal system.
Interestingly, hemolymph can coagulate just like blood, a critical function for wound healing and immune response. Equally fascinating, there are an estimated 10 quintillion bugs alive on Earth at any one time, which means most of the animals walking — or buzzing — around the planet right now don't actually have blood!
What Other Animals Don't Have Blood?
Insects aren’t the only living organisms to have figured out life without blood. Here are some particularly interesting examples:
Jellyfish
These floaty, translucent creatures are about as far from having blood as you can get! Without a circulatory system, jellyfish absorb oxygen directly through their skin. They don't even need hemolymph like insects — they just "breathe" by drifting along in the water.
Sea Sponges
Sponges are some of the most ancient and simple animals out there, with no blood, organs, or even true tissues. They pump water through their bodies to get all the oxygen and nutrients they need.
Corals
These colorful, reef-building animals might look like rocks, but they’re actually living organisms! Like sea sponges, they use the flow of water to absorb what they need, no blood required.
Flatworms
These tiny, flat critters don’t have blood or lungs. Instead, they rely on simple diffusion to move nutrients and oxygen through their body. Think of them as pancake-shaped creatures that let the environment do the work!
