In the warm waters surrounding Hawaii there is a tiny Bobtail squid that can fit in the palm of your hand. Deep inside of it lives a group of microbes that nestle into their mucousy home. The squid has provided them a shelter, free from the stress of marauding predators, greedy competitors, and life-threatening viruses that exist in the ocean water. In return for this luxury of safe space and food, the microbes give back to the squid by glowing brightly. Squid predators hunt from below, searching for a little squid’s silhouette. The light the microbes produce helps camouflage the tiny squid by shining light where a shadow should be. As partners they help each other navigate treacherous waters.
Vibrio fischeri. Credit for the glow of the tiny bobtail squid cannot go to the squid, it goes to a bacterium: Vibrio fischeri. In this case, the bacterial cell is a tiny swimming cell that has a clump of tails at one end of their cell, which allows for movement. They swim around the ocean until one of them enters the squid’s body and starts to settle down into the crypts and mucus of the squid light organ. There they become immobile, multiply, and start to glow by producing bioluminescence. They form a symbiotic relationship with the squid. In return for a place to live inside the squid, they offer camouflaging light that helps the squid evade predators who hunt by detecting silhouettes from below. Without the bacterial partner, the squid are more likely to get eaten.