(Idea from Harold B. White published in Biochemistry and Molecular Biology Education Vol 28 No 1 pp 35-36, 2010.)
If you put eggs under a UV light they will glow scarlet. The same pigment is what makes earthworms purplish, and it is very light sensitive, meaning it's why earthworms fry in the sunlight (say, after a good rain when they come out).
More at this link. I sense a future biochemistry demo!