Animals like the cookie cutter shark are also found in this zone. These animals have an extremely sharp set of teeth that are arranged in a circular pattern so that they can quickly take a chunk of flesh out of a large animal like a shark, dolphin or whale that might swim passed. The fish that live at this level of the ocean don't often get the opportunity to eat and must therefore take advantage of any food that is available. Even though there is no photosynthesis that takes place, oxygen levels in most of the twilight zone is sufficient so as not to represent a survival problem for animals that live at this depth. Protection Animals that live in the twilight zone have evolved a variety of strategies for preventing themselves from becoming dinner.
Many animals have large eyes and are able to see thirty times better in dim light than humans.
Camouflage is one strategy that is useful as to not be seen is to avoid being eaten. Many animals try to merge into the background by avoiding creating a outline against the light coming from the surface. Transparent animals are common in this zone as they allow light to pass through them and do not create a shadow. Examples of these include the larvaceans mentioned earlier, jellies, and many fish eggs and larvae. Others may have silvery surfaces that reflect light.