UH study sheds light on squid's built-in glow
By Timothy Hurley
Advertiser Staff Writer
University of Hawai'i scientists have discovered the key to how the Hawaiian bobtail squid is able to shine its own built-in flashlight to confuse predators.
Photo courtesy Wendy J. Crookes
The discovery, described in the today's issue of the journal Science, may lead to a new generation of optical tools or other microlighting technologies, according to the Kewalo Marine Laboratory researchers.
The Hawaiian bobtail squid uses light produced by colonies of luminescent bacteria to confuse predators.
"We're hoping down the road that this might be used to create small-scale reflective surfaces," said Wendy J. Crookes, first author of the scientific paper.
Although the squid's light is produced by colonies of luminescent bacteria, the beam is powered by stacks of reflecting plates that surround the bacteria. These reflector plates are made from an unusual family of proteins the UH scientists named "reflectin."
The scientific team led by Margaret J. McFall-Ngai conducted the laboratory research over the past year using the offspring of squid scooped from the ocean shallows off Hawai'i Kai and Kane'ohe Bay.
These tiny squid, only a couple of inches long, hunt at night above sandy flats, eating fish and other small creatures, and putting themselves in danger of being eaten by larger fish that tend to hide in the sand, looking up. They are especially vulnerable on bright nights, when the moon causes them to cast a shadow as they hunt in knee-deep water.
But the Hawaiian bobtail squid somehow senses the amount of light hitting its backside and then shines the light below, effectively canceling its shadow.
While the reflective plates of other aquatic species are formed from chemicals called purines, it appears reflectin is unique to cephalopods, the group of animals that includes squid, octopus and cuttlefish, Crookes said.
Crookes said she first observed the oddly shaped protein 10 years ago, but there was no scientific method to identify it. Advances in DNA sequencing made the discovery much easier, she said.
The research team now is studying the beneficial relationship between the squids and the bacteria that produce the light. This symbiotic relationship is common in nature, and even humans have beneficial bacteria in their intestinal tract.
Reach Timothy Hurley at thurley@honoluluadvertiser.com or (808) 244-4880.
