These jellies are all about light, meaning they are all about the dark. Red looks black even just below the surface of the water, and in the deep, where you won't find spotlights, these jellies disappear. In the deep sea, where the bloody-belly comb jelly lives below 1,000 feet in the North Pacific, it is very dark.
These jellies, then, hide in plain sight. Which is a shame, because they're beautiful, especially as the combs are providing us with a bit of light diffraction. Predators and prey never see those incredible colors.
Technically, these are ctenophores, meaning that they are not true jellies, but the name is sticking, even though it is a new one. This species were first collected off San Diego in 1979 and described in just 2001.
