Birefringent communication

[Gamera]

Dr. Caldwell -

I am curious to see if there are any species of stomatopods that use birefringent or irridescent color markings for communication.

I know for a fact that many species of inverts in marine and non-marine environments manufacture cholesteric liquid crystals which are used as communication devices.

I'm curious if any stomatopods use this as a means of communication based on the fact that the stomatopod ocular capacity is relatively high compared to other invertebrate species.

Any references or a general direction to go for information would be appreciated.

Just as a side note, I have a large number of databases available for searching articles. If there's a particular article/abstract database you'd recommend, I could try there as well.

[Gonodactylus]

Gamera,

Certainly there are several species that have structural colors used in displays. Justin Marshall in Brisbane has done the most work quantifying the colors of stomatopods, so you might want to search out some of his papers.

Along these lines is the discovery that I made a couple of years ago that some species have polarized displays. This is most common in the Odontodactylus, but we have found it in several other species as well. If you go to my web page at the University of California Museum of Paleontology site:

http://www.ucmp.berkeley.edu/aquarius/signals.html

you can see picture of the polarized antennal scales of O. havanensis. The uropods do the same thing. There is a picture of this beast without using a polarized filter on the Aquarius web site at:

http://www.uncwil.edu/nurc/aquarius/2001/7_2001/expd.htm

We are trying to figure out how this signal is generated, but so far about all we have come up with is that there are probably a couple of polarized filters and perhaps a pigment involved. This system has some fairly strange properties that I won't go into here.

We know have found a couple of other species that have display spots that look like structural colors, but that are also polarized. This is an area that we really want to pursue given that the eyes are capable of seeing in at least 3 different e-vectors.

Roy

[Gamera]

Okay.

This strikes me as extremely interesting.

To put things in perspective - I'm a graduate student in organic chemistry. I'm not the typical organic chem grad in that I study liquid crystals. I could go on and on about them. They're great. However, the one thing that caught my attention is that while doing some background research on LC variants (there are several classes of LCs) I found that a large number of inverts in nature use a specific class of liquid crystals to communicate amongst themselves. Liquid crystals are manufactured and then locked into place as the invert grows, and allows (for individual species even) for 'customized' signalling. Additionally, the invertebrates have also selectively evolved to be able to see the signals.

The classic example is in scarab beetles. Jeweled scarabs have extremely birefringent shells and in many cases, the sells are actually naturally grown liquid crystal cels that modulate light either by reflecting one type of circularly polarized light, or actually modulating the light to give a particular optic response after light interacts with the shell. Whether or not the beetles perceive and act on this isn't actually well known. Or at least, I haven't found any difinitive theories in any of the liquid crystal papers I've read. (Haven't read any bio papers yet. :p )

So that brings me to the question I asked before. I find it interesting that nature would evolve spatial filters to modulate light for communication much like is done in the telecom industry.

Additionally in works my hobby into my actual research field.

I find it extremely interesting that (in your response) you noticed an optical response to light input. It would be exciting to see if stomatopods indeed manufacture liquid crystals for communication like other invertebrates. It wouldn't be a far fetched idea, and given that stomatopods can spatially filter light, I wouldn't be surprised.

My initial impression (despite not having any understanding of what's going on) is that each species of 'optically active' stomatopod has evolved some means of modulating light to create a specific polarized response. The spatial filters in the stomatopod eyes enable them to see this response, but not the response from other species.

Just a thought... :D

[Angel*Fish]

Not qualified to comment - except to say that this is a fascinating subject!

Gonodacytlus, just to let you know, Gamera is not the only one who enjoyed those links ! Thanks!

[orkspace]

Originally posted by Gonodactylus
We know have found a couple of other species that have display spots that look like structural colors, but that are also polarized. This is an area that we really want to pursue given that the eyes are capable of seeing in at least 3 different e-vectors.


Roy,

Are the orange spots on a G. platysoma examples of this?

Thanks,

Daniel

[Gamera]

I've done some more digging around, and I've found a few articles (unfortunately, not in PDF format) by a collaboration between LC chemists and some biologists that discuss, in detail the mechanism of light 'modification' by the chiton in the shells of the jeweled scarabs.

I found it fascinating. I'll try to put it up for people to look at.

Dr. Caldwell - If I were able to get samples of the 'signaling' spots on some mantises, I could analyze it readily and possibly get a clearer picture of the structure that gives rise to the optical response.

[Gamera]

Dr Caldwell -

I did some scouring around, but I've been unable to find any work done with respect to the phenomenon you mentioned before.

Do you have any materials you could forward me?

[Gonodactylus]

What would be the best type of material. I have lots of dried moltskins that still show some of the polarization. When we place the a uropod or antennal scale in ETOH it looses the polarization.

Roy

[Gamera]

Considering my theory for what is behind the phenomenon that gives rise to the'optically active' mantis, I'm not surprised that putting the material in ethanol destroys optical activity.

With regards to sending a sample, I wouldn't mind having samples of the optically active material sent (though at this point in time, I'd like to get some more background research done first). Currently, I'm digging around to get more specific papers with regards to the optical activity of the structures responsible.

I'll try to get in contact with you once I have some detailed background research done. Additionally, I'll need some time to get instrumentation times set up (powder x-ray), and get myself some time on the PLMs and the other spec instruments.

[Gamera]

Considering my theory for what is behind the phenomenon that gives rise to the'optically active' mantis, I'm not surprised that putting the material in ethanol destroys optical activity. EtOH could easily be denaturing the structure that gives rise to the polarization. If my theory is spot on, it's not only the compound that gives rise to the response, but the macroscopic structure in the surface. Denaturing the material destroys the structure and therefore, destroys the response.

With regards to sending a sample, I wouldn't mind having samples of the optically active material sent (though at this point in time, I'd like to get some more background research done first). Currently, I'm digging around to get more specific papers with regards to the optical activity of the structures responsible.

I'll try to get in contact with you once I have some detailed background research done. Additionally, I'll need some time to get instrumentation times set up (powder x-ray), and get myself some time on the PLMs.

[Gamera]

Out of curiosity, what experiments have you conducted to try to deduce the composition of the 'optically active' spots on the mantis?

[Gonodactylus]

THis has proved to be extremely difficult. We wanted to depolarize the signal, but all of the materials that we have found also degrade the other optical qualities of the signal. Heat fractured pyrex seems to be a good option, but so far we haven't been able to create a fraction pattern fine enough. The other problem that we have is that there is a strong UV signal coming off the same structures (apparently not polarized) and we have to be careful not to knock that out. This is a sticky one.
Roy

[Gamera]

Have you been able to determine if the light returned is plane polarized or circularly polarized?

I haven't been able to scrounge up instrument time (physicists are notoriously slow), but one thing I think may be useful is to try to determine if the light returned is being polarized by the materials or if the response is simply rotation of polarized light. Additionally, you may be getting selective reflection of circularly polarized light (of a particular handedness) which is coming back and detected as rotated polarized light.

[Gamera]

It's been a while, but I thought I'd drop a line just to make sure you know that I'm still thinking about this.

I also have found a nice little tidbit of information you might find very interesting.

I would check up on the following ACS journal citation:

Srinivasarao, Mohan. Chem. Rev. 1999, 99, 1935-1961.

It is a solid review article about different kinds of optics oriented techniques used in communication developed by insects. Of particular interest is the latter half of the article regarding beetles.

I haven't followed up completely on the references yet, but I will be soon. Let me know if this strikes you in any way as being the solution to your communication conundrum. :D

[Gamera]

Dr. Caldwell -

If you have any of the material that is optically active on hand that you can send out, let me know. I have some time on the power diffraction xray that may give me an idea of what the structure of the stuff is. Additionally, I may be able to get some time on a TEM instrument or AFM to probe the surface structure.