The Light Organ of the Hawaiian Bobtail Squid

A NOCTURNAL hunter, the Hawaiian bobtail squid creates its own light​—not to be seen, but to be unseen—​to blend in with the ambient moonlight and starlight. The animal’s secret is its partnership with light-emitting bacteria. That partnership may also hold secrets that could benefit us, but in a seemingly unrelated way. It may benefit our health.

Consider: The Hawaiian bobtail squid lives in the clear coastal waters of the Hawaiian Islands. Light from the moon and the stars would normally make the silhouette of the creature stand out to predators below. The bobtail squid, however, emits a glow from its underside that mimics ambient night light in both intensity and wavelength. The result is stealth​—no silhouette, no shadow. The squid’s “high-tech” apparatus is its light organ, which houses bioluminescent bacteria that produce just the right glow to camouflage their host.

The bacteria may also help to regulate the squid’s sleep-wake pattern. This interests researchers because the bobtail squid may not be the only creature where there is a link between bacteria and circadian cycles, or daily rhythms in activity. In mammals, for example, bacteria that play a role in digestion may also be associated with circadian rhythms. Disturbances of these rhythms have been linked to depression, diabetes, obesity, and sleep disorders. Hence, the study of the squid’s bacteria-host system may furnish insights into human health.

What do you think? Did the light organ of the Hawaiian bobtail squid come about by evolution? Or was it designed?