If you do any diving anywhere, you will see sponges everywhere. Some of them are more colorful than corals, and some of them you can sit in. All sponges are water pumps and filters, which makes them useful in the sea and in our reefs. Sponges don’t move, they sit there, eat, and get fat. A typical sponge can pump 20,000 times its own volume in water through its cells in one day. All that water is also filtered by the sponge using “choanocytes,” which are just tiny, cone-shaped towers with sticky cells on them to catch food. Each tower has one flagellum, or hair-like thing. The flagellum waves back and forth very fast, creating a pretty strong current through the animal.
The internal structure of a sponge is made of a substance called “spongin.” I wonder where they got that name. Spongin can contain either calcium carbonate, like corals, or silicon dioxide, which is the stuff they made your car windshield out of. Another word for it is glass. MORE