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UltravioletPhotography

True color UV is 308nm, 335nm, 383nm?


dabateman

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I didn't see this paper discussed yet here:

https://doi.org/10.1016%2Fj.cub.2014.05.071

 

But has teased out the two main UV pigments being 335nm and 383nm. Then worked out the Mantis shrimp filters to see how they see in color UV.

 

I do like my close 313nm, 335nm and 390nm filters for difference in UV. Switching the 335nm with 370nm one sometimes. So interesting to see this in nature.

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How cool, thanks for sharing David. Be interesting to try and reconstruct what it is they are actually seeing with these wavelengths. It does beg the questions of why have they evolved senstitivity to these specific wavelengths though.
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enricosavazzi

[...] It does beg the questions of why have they evolved senstitivity to these specific wavelengths though.

From my reading some of the literature on mantis shrimps several years ago, it seems that their eyes are fine-tuned to allow intraspecific recognition. These "shrimps" (actually stomatopods) usually have eye-spots and other color markings on normally hidden parts of the appendages, which are displayed in intraspecific signalling and "gesturing" at a distance (as well as a remote threat against potential predators). This may well extend into the UV, although it has been studied primarily in the VIS. Several stomatopod species often share the same general environment, and it is therefore useful to them to remotely recognize conspecific members. They also tend to be territorial, hence the usefulness of remote signalling as a way to avoid direct territorial confrontation.

 

Stomatopods are also interesting because of the shape of their eyes. They are oblong with a flat or slightly concave central portion. A few rows of individual ommatidia on the two outer lobes of the eye flanking this central region converge their optical axes at a distance in front of the eye, which at least in principle allows each (composite) eye to provide a "binocular" vision independent of the other eye. This in turn allows the eye stalks to move independently of each other, for example to "keep an eye" simultaneously on two potential preys or threats. Some of the ommatidia along the central strips also detect polarized light. I have seen mantis shrimps pivoting one eye perpendicular to the other when concentrating their attention on another organism, perhaps to simultaneously image the subject in two different polarization directions and/or to apply binocular vision along two different axes (much the same as the cross-type AF sensors on modern mirrorless cameras, which prove superior to the simpler line-type AF sensors).

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Yes their vision is fascinating. They can even see circular polarizer light.

 

But since we know that there is very little UVB, then why would they see at 308nm?

 

I wonder if there are fish or animal currently unknown to us, that may emit or bioluminess UVB light to atract prey. Or use it for short range communication.

 

I doubt the level of UVB from the sun is the reason for their detection. But I don't know. It really interesting.

 

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enricosavazzi

But since we know that there is very little UVB, then why would they see at 308nm?

Again quoting literature from memory, I recall that the proportional amount of UV in sunlight increases near sunrise and/or sunset, so UV vision, even in UVB, might be a selective advantage at times when overall illumination levels are low. This was used as a tentative explanation for UV vision in bats, if I remember correctly.

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