An Eye on Bioluminescence

Scientists have discovered that a small squid, the Hawaiian bobtail, camouflages itself using a bioluminescent organ that utilizes the same genes found in the squid’s eye. The squid are able to physically light up their undersides using a “light organ” so that, when viewed from below, they blend in with the above sunlight and ocean surface and do not cast a conspicuous shadow. This effective survival technique, not dissimilar to other squid species’ ability to discharge black ink, is used to elude patrolling predators.

The significance of this discovery, as explained by UCSB evolutionary biologist Todd Oakley, is the remarkable similarity between the genes found in the bobtail squids’ eyes and the genes found in the light organ. “This is significant because it is an example of how existing components can be used in evolution to make something completely new,” said Oakley in a written statement. “These components existed for use in the eye and then got recruited for use in the light organ. The light organ resembles an eye in a lot of ways. It has a lens for focusing the light. It has the shape of an eye, and now we found that it has the sensitivity of an eye as well.”

Oakley, who performed the evolutionary analysis of the squids’ genes, used an analogy to describe the parallel use of biological components within an organism. “Evolution acts a lot like a tinkerer and assembles what’s available to make something new,” he said. The biologist went on to explain the squids’ bioluminescent abilities stem from bacteria that live within the marine creatures’ bodies – the bacteria themselves produce the light by forming a chemical reaction. The squid don’t control the chemical reaction directly, but they can change their light organs to make them more or less open or, in other words, to let out more or less light, Oakley explained.