What mechanism, emitted by some deep-sea prey, may assist penguins in locating food in dark or deep oceanic conditions?

Answer

Bioluminescence emitted by some of the squids and fish they pursue

Scientists theorize that in the deep ocean or at night, penguins may be aided in locating prey by the bioluminescence emitted by some of the squids and fish they pursue.

What mechanism, emitted by some deep-sea prey, may assist penguins in locating food in dark or deep oceanic conditions?
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