Exploring Our Fluid Earth

Those guys, not just the migrating ones, live a kind of in-between existence. Although the midwaters where they live are dark, there is some light available. Compared to the well-lighted zones above, there is a lack of food. Many of the adaptations of these animals helps them survive in the face of low food availability. Photophores are common and probably help with communication and predator evasion. Many are red in color, since at the mesopelagic depths, all red wavelengths has been filtered out, making the organisms appear black.