This deep-sea fish, <a href="//commons.wikimedia.org/wiki/Photostomias_guernei" title="Photostomias guernei">Photostomias guernei</a>, has a built-in bioluminescent "flashlight" it uses to help it see in the dark.
Edith Widder/HBOI
1999
<a rel="nofollow" class="external free" href="http://oceanexplorer.noaa.gov/explorations/04deepscope/background/deeplight/media/fig3a_400.jpg">http://oceanexplorer.noaa.gov/explorations/04deepscope/background/deeplight/media/fig3a_400.jpg</a>