MADISON, Wis. The small but charismatic Hawaiian bobtail squid is known for its predator-fooling light organ.
To survive, the nocturnal cephalopod depends on a symbiotic association with a luminescent bacterium that gives it the ability to mimic moonlight on the surface of the ocean and, in the fashion of a Klingon cloaking device, deceive barracuda and other fish that would happily make a meal of the small creature.
The relationship between the squid and the bacterium Vibrio fischeri is well chronicled, but writing in the current issue of the journal Proceedings of the Royal Society B, a group led by University of Wisconsin-Madison microbiologists Margaret McFall-Ngai, Edward Ruby and their colleagues adds a new wrinkle to the story.
"The squid has seen an opportunity to recruit an organism to make light," explains McFall-Ngai, a UW-Madison professor of medical microbiology in the School of Medicine and Public Health. "But to do that you have to tame it. You have to train it to do what you want it to do."
In the case of the bobtail squid, it seems that the blood pigment hemocyanin plays a dual role in helping the squid recruit and sustain the bacterium it uses to avoid predation.
Like its human analog hemoglobin, hemocyanin is primarily responsible for transporting oxygen from the squid respiratory system to the rest of the body. But the hemocyanin protein also appears to be deployed in a way to help the squid recruit its population of Vibrio fischeri, which the squid flushes and replenishes on a daily cycle to enable its nocturnal defenses.
"In the early events of symbiosis, hemocyanin appears to have antimicrobial activity," says Ruby, also a UW-Madison professor of medical microbiology and a co-author of the new report. "We think it is part of the mechanism by which Vibrio fischeri become specific."
In essence, the squid is using the antimicrobial properties of
|Contact: Margaret McFall-Ngai|
University of Wisconsin-Madison