SPIDER SIGHT

[Portman CS]

Hi folks,

For the first time ever, I was asked a question at a spider presentation that I could not answer (or at least bluff). At a school recently, a girl said "What colour do tarantulas see in?".

I have leafed through my not inconsiderable library and come up with an answer but I would like to throw it open to you learned fellows.

Well...what colour DOES a tarantula see in?

Carl

[Leon Lane]

Never thought about this one.... I'm sure I remember reading that tarantulas can differentiate between various shades of light and dark but I don't remember anything about actual colour.

[Phil Rea]

As far as I have understood, they are thought to be able to distinguish movement and differentiate between dark and light.

[Adam Smith]

As the others have said I have read and heard they can see various shapes and shades of dar kand light and for short diastances. This is all presumed through years of study but how would one know what a spider sees? After asll it took humans ages to know what dogs and cats see through their eyes but even at that could be wrong. It poses many questions, more than answers. Maybe an experiment could be conducted.

[Portman CS]

Re: SPIDER SIGHT

For the first time ever, I was asked a question at a spider presentation that I could not answer (or at least bluff). At a school recently, a girl said "What colour do tarantulas see in?".

Yes chaps, I concluded also that they see light and dark, but how DO we know this? I looked in the Biology of Spiders books etc but was not totally satisfied with what I found. I shall research this a little more if I can. I want to know if theraphosids see differently to araneomorphs. I know that some tue spiders have excellent eyesight (salticids, wolf spiders etc) but do they see in the same way or do they see in colour?

Thanks for replying. Keep me posted if you find anything else out.

Carl

[David Flanagan]

Most of this article is way over my head but you may want to check it out.

Dahl,R. D., and A. M. Granda. 1989. Spectral sensitivities of photoreceptors in the ocelli of the tarantula, Aphonopelma chalcodes (Araneae, Theraphosidae). J. Arachnol., 17:195-205

On page 10 it says "Aphonopelma may therefore respond simply to the fundamental dimension of ambient light intensity. Complexities of wavelength discrimination and contour perception are apparently not involved, for the visual system here is functionally homogeneous and shows none of the response complexities seen in color discriminating eyes."

Cheers,
David

[Phil Rea]

That's an interesting paper David, thanks

[Matjaz]

An ocellus is a very simple pigment eye with one pigment type. So physically, you need more types of sensors within an eye, each sensitive to it's "basic" colour (wave lenght)...and the result (the mix) of this types is colour seeing. This means it's imposible to see colour with an ocellus.

[Larry Loos]

mygalomorph sight

Whether or not tarantulas can, or cannot see is pure speculation on a forum such as this. There are no real studies that I can recall that actually prove positive whether or not they can see. It is generally felt that they can determine various shades of dark or light as they react to light in a mostly negative way which is obvious to most hobbyists but that is it.

It is more likely that they sense a presence with their sensory organs, that being their setae or, filiform bristles. These bristles are so sensitive as to be able to detect a fly a meter away according to Schultz & Schultz [The Tarantula Keeper's guide, second edition.]

Upon close exam of a larger exuvium, specifically the carapace, if one examines the Ocular Tubercle with a high power microscope or, a jewler's loop you can see quite clearly the eye sockets [for lack of a better term ] and you will notice that not only are they quite clear but, in the center of each is a small, round, clear and quite noticeable object not unlike a pupil. It too is clear and in the anterior and posterior sets of eyes especially round in appearence. Very interesting. What this is and what is function is remains a mystery to me at this time. But it has some function.

This is not to say that they can "see" as we relate to sight but it shows a need for further study into mygalomorph eyesight or, the lack of.
As far as I know only the jumping spiders have enough eyesight to see anything and that would most likely be only a few centimeters, [speculation on my part]. If any of the so called tarantulas would have or could have better sight than others it would make sense that it would be aborals due to their lifestyles off the ground even though most don't live far off the surrounding substrate. This is simply an unanswered question for me at least at this time.

[Matjaz]

The question is, do spiders see colour or not...not if they see at all. Of course they can see. Sight is a reaction to light (photons) - an eye is an organ that reacts to stimuli of that type. But you're right about the poor eyesight...ocelli are very simple (primitive) eyes so the spider's main sensory organs are the mechanoreceptors (setae). Oh and, there are studeis about this type of eyes, you can be sure about that.

[Larry Loos]

Spider eyesight

Matjaz- I do not believe that tarantulas, having simple eyes that they do can see color but, that is pure speculation on my part and unless linkable study can be provided then it must be assumed that what they can detect is simply the difference between shades of light and dark. that is easily proven. Most hobbyists can see that for themselves through simple reactions on the part of the animals they keep.
What we speak of here are possibly simple shades of gray but no "sight" as we can relate to it.
If shapes were involved, they would not be anything we could relate to I cannot provide a link to our forum here without first asking if that would be ok with the members involved with that thread but the pictures that were posted for other members concerning site were of the upmost quality and provided by a British memeber to boot.

These clearly showed the eyes sockets up close and what I had been speaking of. As for the remainder of your post you are totally correct. What they do use to sense our presence is of course their filiform bristles or better known as setae which if no barriers involved and unrestrained tarantula would most likely to be able to detect our presence in the room through simple movement of air even without the vibrations of our physical contact with the floor.
That is why they react the way they do when you try and lower a capture cup over them. It is not the cup they see although they make detect the presence of one's hand looming overhead, but rather the sensory overload as you lower the cup and the rush of air activates their sensory bristles. That is what causes them to try and avoid capture in that manner. If you lower the capture cup extremely slowly it may be possible to almost cover them before they detect the cup depending on your patience.

[Matjaz]

I agree with the speculation that they can't see colour...even more, I'm convinced they can't see colour becouse of the simple physical logic (I tried to explain that in my firts post), although I didn't read any articles about the topic of colour seeing. But I'm absolutely sure there are such studies (the articles are probably not for free on the internet though). Anyway, what I wanted to say is that I'm not here to argue with you, I just like such topics that are a little more, how should I say, scientific maybe...we can search for articles on that topic together and convince ourselfs (but I'm gonna do that after the holidays (ours are a little longer so be patient).

Matjaz

[Larry Loos]

RE: eyesight

Welcome to the cold and impersonal world of computers. There is no argument here but rather "discusion." I think it fair to say that mygalomorphs do not really see in any way that we can relate to. Simple as that.

[Matjaz]

If you can't relate to that (whatever that means) it's your "problem"...no doubt about that. I say an animal with eyes does see, we're not the only animals that can see, just becouse we have much more evolved eyes. Simple as that. I think that's fair to. I also think there's no sense in further discussion.

[bobgepstein]

Spidering ESP

My spiderlings hardly hunt by sight anyway so it seems a moot point. They almost rely entirely on the sensation through their feet.

Half the time the cricket is out of any direct line of sight and the spiders still launches itself in the right direction.


Bob.