Ultraviolet

A hippo's red 'blood sweat' is neither blood nor sweat. Lacking sweat glands, hippos ooze red fluid from special skin glands. Kyoto researchers found its pigment, hipposudoric acid, acts as a natural UV sunscreen and an antibiotic.

Tardigrades survived 10 days exposed to the Vacuum of Space and cosmic Radiation in a 2007 ESA experiment. Some even endured solar UV; after rehydration on Earth, they revived and laid eggs—the first animal shown to survive such exposure.

Under UV light, a scorpion glows cyan-green because fluorescent compounds in its cuticle absorb UV and re-emit visible light. Why is debated: sunscreen or light sensor. A freshly molted one stays dark until its shell hardens.

The northern blue-tongued skink's tongue does more than look blue — it strongly reflects ultraviolet light, with the rear reflecting roughly twice as much as the front. Normally camouflaged, it gapes its mouth at predators to flash the UV-bright rear in a deimatic display.

A giraffe's tongue reaches 45–53 cm with a tip colored deep blue, black, or purple. The dark hue comes from melanin, and the leading explanation is ultraviolet protection: giraffes spend 16–20 hours browsing with the tongue out, so its most exposed part needs sunscreen.