Friday Squid Blogging: Squid Also See Through Non-Eye Organ

Weird:

The UW-Madison researchers have been intrigued by the light organ's "counterillumination" ability -- this capacity to give off light to make squids as bright as the ocean surface above them, so that predators below can't see them.

"Until now, scientists thought that illuminating tissues in the light organ functioned exclusively for the control of the intensity and direction of light output from the organ, with no role in light perception," says McFall-Ngai. "Now we show that the E. scolopes squid has additional light-detecting tissue that is an integral component of the light organ."

The researchers demonstrated that the squid light organ has the molecular machinery to respond to light cues. Molecular analysis showed that genes that produce key visual proteins are expressed in light-organ tissues, including genes similar to those that occur in the retina. They also showed that, as in the retina, these visual proteins respond to light, producing a physiological response.

"We found that the light organ in the squid is capable of sensing light as well as emitting and controlling the intensity of luminescence," says co-author Nansi Jo Colley, SMPH professor of ophthalmology and visual sciences and of genetics.

Posted on June 12, 2009 at 6:46 PM • 7 Comments

Comments

Chris SJune 13, 2009 11:30 PM

Integrating the light sensor with the light producer is a nice trick, but the counterillumination is well known.

Hatchet fish might be the best examples, but squid have been known to do this before...

http://www.bio.davidson.edu/people/midorcas/...

Interestingly, many military groups have discovered the value of counter illumination as part of camoflage.

dot tilde dotJune 15, 2009 6:54 AM

@chris s, military value:

... and that is known too, or do you happen to have a link at hand?

.~.

Chris SJune 15, 2009 1:18 PM

Military usage can start as something as simple as dazzle camoflage for boats, and includes such classics as painting the bottom of aircraft sky blue.

More recent items would include this...

http://www.wired.com/dangerroom/2008/05/...

... where illuminating the leading edges of the wings on a drone makes it almost impossible to see until much closer in.

This article...

http://jmrc.tripod.com/fa/stealth/stealth2.htm

... details similar projects in WWII and Vietnam using bright lighting on aircraft to reduce their visibility.

JakeJune 25, 2009 3:24 PM

how does the squid know how bright to make its light organ? Does it detect (with eye or light organ) the brightness of the ocean surface above it? figure water pressure, convert it to depth, and then to required illumination level? something else?

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