Giant clams manipulate light to assist their symbiotic partner | Hacker News Reader

Giant clams manipulate light to assist their symbiotic partner

phys.org

48 pointslelf14 comments

Another great example is Aliivibrio fischeri [0]. Generally, squids are subject to predators as they group together and at night. The light of the moon creates a shadow that predators recognize as a group of squid. These squids have a special organ that lets in these bacterium that when in sufficient numbers, called quorum sensing, actually light up. All these bacterium glowing at the same time reduces the shadow and protects the group of squid. The bacterium are provided a safe space and therefore this is a great example of symbiosis.

0 https://en.wikipedia.org/wiki/Aliivibrio_fischeri#Symbiosis_...

I've seen schools of reef squid at night and your description confused me. The Aliivibrio fischeri, according to the Wikipedia article, are only found in Hawaiian Bobtail Squid which I've never encountered before.

I've seen other types of Bobtail Squid, which were all tiny, solitary, and found on the sea floor. It sounds like the bioluminescence is just enough to overcome the moonlight shadow as they hover above the bottom. Very cool, thanks for the link.

They're not just found in that one squid, that squid just happens to be the model organism labs study. They symbiose with many other organisms as well

Sure enough, it is too late to edit my comment but the Wikipedia page says:

> A. fischeri have been most studied as symbionts of marine animals, including squids in the genus Euprymna and Sepiola, where A. fischeri can be found in the squids' light organs.

Clicking through the genus Euprymna and Sepiola links, it looks like these are all Bobtail-Squid-like. I shouldn't have used the word "only" but that wasn't the source of my confusion. My issue was the word-picture of a school of reef squid, found in the upper water column, using bioluminescence to overcome moonlight shadows. It didn't make sense. Bobtail Squid, on the other hand, are tiny bottom feeding animals. They are not what I think of when you say "squid" without qualification.

However, the images of Bobtail Squid on Wikipedia do not make their half-your-thumb size obvious and the silhouette image [1] makes it look like an upper water column phenomena. When I first realized we were talking about Bobtail Squid, I thought of the blue lights some people put under their cars.

[1] https://en.wikipedia.org/wiki/Bobtail_squid#/media/File:Bobt...

V/A fischeri (a lot of people still haven't gotten used the renaming from vibrio) is really fascinating. Slight point of clarification- quorum sensing happens between the bacteria where they detect the amount of other bacteria present, not through a signal from the squid. It's a phenomena that has a lot of importance in bacterial disease and infections as well - one of those classic cases where a scientist that wanted to study a random cool phenomenon ("but why squid glow?") advanced a fundamental understanding with broad implications. You can see quorum sensing in action by culturing some V fischeri in a petri dish and observing luminescence when they read high enough numbers. You might be able to buy an educational kit online - it's not a dangerous bacteria (my professor let us take home our plates to culture them out to see them glow in our dorms). Super cool stuff.

I probably just phrased it wrong, but yes, that's what I meant. The bacterium conduct the quorum sensing when enough of them are in the squids specialized sac.

When I read the parent comment I did not detect any suggestion that the squid communicates with the bacteria. It seems like you read this into the comment.

Pictures don't do giant clams justice at all. Seen in person, they glow like something from outer space--like galaxies or nebulae or some kind of sci-fi light creature.

Indeed they are quite "vibrant", as the article states:

> This may also explain the mantle colors of giant clams. The idea is that the vibrant colors of giant clams are not due to optical differences in the tissue, but rather differences in the distribution or abundance of symbionts relative to iridocytes in each individual.

That is pretty cool and awfully nice of these clams. It could indeed be inspiration to interesting tech. We already have amazing technology for light modulation if you take a look at a DPL beamer. This tiny chips have millions of tiny mirrors controlled by gas. At least TI does, I don't know if others have made progress here in the meantime. An incredible technology everyone takes for granted.

Changing the wavelength isn't trivial, this sounds very interesting. I don't know any techniques aside from passing it to another medium.

Changing the wavelength like this is called https://en.wikipedia.org/wiki/Fluorescence and is the basis of fluorescent lights.

Original paper [1]:

[1] https://repository.kaust.edu.sa/handle/10754/663708

Wavelength shifting for cooperative effect. Very interesting and beautiful phenomenon. Fluorescence is pretty cool, 'fluorescent symbiosis,' is certainly new to me.

So are there any plants able to do the same? An entire wavelength of light seems to be pretty valuable energy real-estate.

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