Hawaiian bobtail squid, Euprymna scolopes, in front of diving mask. This squid lives in a symbiotic relationship with the bioluminescent bacteria Vibrio fischeri, which inhabits a special light organ in the squid's mantle. The bacteria are fed a sugar and amino acid solution by the squid and in return hide the squid's silhouette when viewed from below by matching the amount of light hitting the top of the mantle, (counter-illumination). From Midway Island