Living Glass

What would you do if your skeleton were made of glass?  Maybe you’d be a sponge.

- Galadriel Watson

Most creatures in the ocean build their shells and skeletons out of hard calcium—the same mineral that’s in our own bones. But the delicate glass sponges are different. These simple animals build their skeletons out of silica—the stuffof glass.

To make its skeleton, a glass sponge pulls tiny bits of silica out of the water. The sponge assembles the silica into glassy spines, called spicules, which it fuses together into a skeleton. Up close, the skeleton looks a bit like a net woven of thin glassy fibers. This makes a scaffold that gives shape to the living tissue, similar to our own bones.