so i was hacking my liverock, and OMGWT*BBQ, this thing appeared. a 10" long bristleworm when fully extended. It broke in half, and this extremely beautiful, yet creepy, luminous blue fluid appeared. I have no idea what it was, but i assured u it was glowing in my dimly lit kitchen.
The only conclusion i can, well...conclude, from this is because invertebrates have haemocyanin in their blood, which is copper based and contains Cu2+ ions, giving it a bright blue colour, instead of the red blood we humans have.
stunning isnt it hehe. btw, no photoshopping! its this blue! now if only all corals came in this colour.