Book 30, Question 53
What is a water flea, and can you see its heart?
Daphnia, or water fleas, are tiny see-through animals about as big as a poppy seed.
They are not insects but crustaceans, relatives of shrimp and crabs. They swim with jerky hops using branched antennae, and they filter algae from the water. Under a microscope, you can see a heart beating inside their clear bodies, and sometimes eggs inside.