This a cross-section of the tentacle of a sea anemone, showing the algal symbionts living inside of the tentacle in magenta, and a fluorescent protein synthesized by the anemone that acts as a protective antioxidant in green. Blue shows DNA in cell nuclei, and white shows filamentous actin, which is a marker of cell surfaces.

I took this image as part of a study in which I was trying to understand why these animals produce fluorescent proteins in their natural environment. We use fluorescent proteins, such as GFP, as tools in our research, but these animals synthesize them naturally for reasons we didn’t understand.