Fiber optics as light conductors are obviously not just a recent invention. Sponges (Porifera), the phylogenetically oldest, multicellular organisms (Metazoa) are able to transduce light inside their bodies by employing amorphous, siliceous structures. Already more than ten years ago, the finding of photosynthetically active organisms inside sponges raised the question, how they could survive there in an otherwise presumably dark space. As early as that time, marine biologists have hypothesized, that light might be transferred inside the sponge body.

Source: About Heartburn / GERD