Most fish that live in the deep ocean are black or red, colors that make them nearly invisible in the faint blue light that reaches their depths. The deep-sea anglerfish, by contrast, carries a lure that glows brightly, lit by bioluminescent bacteria.   this conspicuous feature does not undermine the fish’s concealment; instead, it exploits the tendency of prey to approach sources of light, drawing them within reach of a body that remains all but invisible.