Friday's fun fact - X marks the spot

The most distinctive feature of Pristella maxillaris is its translucent layer of skin that covers its body, hence its more common name X-ray fish. Did you know their skin is thought to be a form of protection as it makes them harder to spot amongst dense vegetation and shimmering water?

The transparency of this little fish reminded me of a photo I saw used to promote blood donation ahead of the Olympics. It is a very striking image which is obviously what they wanted as it certainly catches your attention.