The Bloodybelly reaches some 12 cm (4.5 in) long and lives in depths of 700 to 1,000 metres (2,300 to 3,300 feet). There is still a bit of light here, but red wavelengths are absorbed more quickly than other colours by all that water above. It means that being red is a really good way of disappearing into the gloom, since red looks just like black down there.
Bloodybelly Comb Jellies are Lobates, which means they have something that looks like a huge pair of lips surrounding their mouth. These lobes trap the tiny prey Comb Jellies feed on. And since a lot of their prey are probably bioluminescent, a deeply pigmented stomach ensures their belly doesn't light up in the dark to attract dastardly predators.
Isn't it always the way? We'd all love to open our hearts and let the light shine but there are simply too many teeth around. Oh, dear... I'm getting soppy!