Known as the twilight zone, the mesopelagic zone meets the photic zone above and becomes very dark as depth increases. Temperature decrease; pressure increases. Because nutrients are limited here, some animals rise to the photic zone at night for food. Many animals in this subzone can eat animals larger than themselves because they are equipped with large sharp teeth with expandable jaws and stomachs. Another key physical feature of animals living in this zone is ____________, which has a variety of purposes, including predator deterrence, communication, and lures for prey.
A) symbiosis
B) transparency
C) bioluminescence
D) over-sized scales