OK, this could equally fit into the 'Physiology and Biology' forum, but I thought I would post this article here. The recent discovery of bioluminescence in the deep water octopus Stauroteuthis has some interesting evolutionary implications: Science Daily Article - Stauroteuthis and there is a great video of Stauroteuthis here (along with a few others): Stauroteuthis Video I'm sure Steve and Tintenfisch could correct me, but it seems that this is the only cirrate octopus which displays bioluminescence. The implication here is that the animal's suckers evolved a secondary function of bioluminescence as the animals ancestors adopted increasingly deep water habitats. The original function of the suckers, i.e to grasp rocks and the sea floor, became redundant, as the creature slowly adapted to a deep water pelagic niche. Slowly the suckers changed from their original function to that of a light producing organ, probably to attract prey items such as copepods. (Kat mentioned this in her article on Deep-Sea Cephalopods). It seems we are looking at a fascinating example of evolution in action!