How Do We Know Tarantulas Have Bad Eyesight?

CABIV

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I was thinking about this the other day, and I was curious how we know they can't "see" that well.

You could not easily give the tarantula an eye test, since it can't speak or really report back to you directly. Indeed, tarantulas seem to be indifferent to their surroundings.

Do we know this via cellular studies? What is the scientific method for determining eyesight in tarauntulas (and other invertebrates)?
 

ledzeppelin

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Im no scientist, but there are methods that determine the general sight of animals, which colors they see.. It depends on a number of some receptors and stuff like that.. To answer with a practical example: if they (Ts in particular) had good eyesight, they wouldn't web on the floor so much.. Webbed floor enables them to feel the movement of prey and predators. If their eyesight was good, they would hunt openly, like a praying mantis would, for example..

This is just a laypersons answer.. I'm sure many will follow with more scientific content :)
 

Chris LXXIX

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Aside for the Goddess 0.1 Pelinobius muticus PBUH (Peace Be Upon Her). She can see pretty well and granted me the honor to be Her devoted & humble Priest u_u
 

Bugmom

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I was thinking about this the other day, and I was curious how we know they can't "see" that well.

You could not easily give the tarantula an eye test, since it can't speak or really report back to you directly. Indeed, tarantulas seem to be indifferent to their surroundings.

Do we know this via cellular studies? What is the scientific method for determining eyesight in tarauntulas (and other invertebrates)?
I don't think they're indifferent to their surroundings in the least, they just "see" their world differently than we do, because their world is what they can feel and probably smell, too. A female tarantula knows a male has come a-callin' because she feels his vibrations from tapping. This is similar to the mating dances with birds - the arachnid equivalent of bright plumage and Riverdance moves. Birds need those displays because birds rely on their eyesight to navigate their world. Tarantulas rely on the vast number of sensitive setae covering their bodies. Although I'm not sure why jumping spiders are as hairy as they are, given their relatively good eyesight, but on the other hand, they're not tarantula levels of hair.

But then you wonder, why are some tarantulas "hairier" than others? Bumba cabocla is hardly "hairy" at all. Does this mean that species has better eyesight than Brachypelma albopilosum? o_O Heck if I know. Someone answer this!
 

Venom1080

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they wait for prey to come to them. if you ever see a tarantula run after a cricket from across the cage let me know!
seriously though, if youve ever kept wolf spiders, youd see how a spider with good eyesight hunts compared to a tarantula.
 

Devin B

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I think its because they have a hard time reading the paper unless its fairly large print, or if mine are wearing their glasses (which are really thick). Also tarantula glasses are really expensive.
 

Ungoliant

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I was thinking about this the other day, and I was curious how we know they can't "see" that well.

You could not easily give the tarantula an eye test, since it can't speak or really report back to you directly. Indeed, tarantulas seem to be indifferent to their surroundings.

Do we know this via cellular studies? What is the scientific method for determining eyesight in tarauntulas (and other invertebrates)?
A lot of this information comes from Biology of Spiders, and I would encourage you to get a copy of this book if you want to learn more about spider anatomy, physiology, and behavior.

Most spiders don't rely heavily on vision but tactile and chemical cues. For example, orbweavers can only see differences in light levels, which helps them entrain their circadian rhythms to the day/night cycle. Their eyes don't form clear images, and they rely mostly on the vibrations transmitted through their webs to know what is going on around them.

Hunting spiders (such as jumping spiders and wolf spiders) tend to have better eyesight, which is usually indicated by the presence of large median eyes. (Jumping spiders have the best vision of any spider. Not only do they see in color and have binocular vision for gauging distance, but they can see ultraviolet and polarized light.)

Animal vision is assessed in a variety of ways. First, you can study the anatomy of the eye. As noted in Biology of Spiders, "the efficiency of any eye is determined by the design of its optics and by the structure of the retina. Both are well developed in jumping spiders." Tarantula eyes seem more similar to those of other spiders with less acute vision, although I would not be surprised if arboreal tarantulas like Avicularia that need to navigate trees could see a little better than terrestrial tarantulas that hunt from burrows.

You can observe their behavior in the field. For example, there is a species of wolf spider that navigates differently on sunny days that on cloudy days, indicating that it is using the sun and/or polarized light. Jumping spiders continually orient themselves to track prey and other things that catch their attention.

In artificial settings, you can deprive them of certain sensory inputs and see how they behave. For example, many jumping spiders don't hunt well in darkness or red light (the end of the spectrum they can't see well), whereas a web-dwelling spider can capture prey with or without light.

You can try to test their ability to distinguish between objects, such as objects of different colors.

Placing a mirror in front of a spider can show whether the spider is seeing an image of itself. (There are lots of cute videos of male jumping spiders making threat displays at "the other male" in the mirror, whereas tarantulas seem indifferent to their reflections.)

You can place 2D images or 3D models of prey or other spiders before the spider and see if it reacts without any tactile cues like motion.
 

ledzeppelin

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Im interested what's the deal with P. irminias.. They sure can jump, so they must see where they're jumping?? Or do they just hope they'll hit a branch or sth?
 

Ungoliant

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Im interested what's the deal with P. irminias.. They sure can jump, so they must see where they're jumping?? Or do they just hope they'll hit a branch or sth?
I've wondered that about Avicularia as well. It may just be a "leap of faith" that they take to escape a desperate situation. (In their natural habitat, there is a good chance that they will be able to grab onto a leaf or branch on their way down.)
 

Venom1080

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Im interested what's the deal with P. irminias.. They sure can jump, so they must see where they're jumping?? Or do they just hope they'll hit a branch or sth?
if you had the choice of being eaten by a monster or jumping off the hand to a uncertain fate, what would you do? ;)
its a last resort Avics do to escape predators, not to mention they live in trees and plants wheres theres almost always something beneath them.
 

ledzeppelin

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if you had the choice of being eaten by a monster or jumping off the hand to a uncertain fate, what would you do? ;)
its a last resort Avics do to escape predators, not to mention they live in trees and plants wheres theres almost always something beneath them.
That's true, but I do imagine that arboreals have better eyesight in general.. I think they need it more
 

dopamine

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Tarantulas are the last spiders in the evolutionary line. True spiders, notably hunting spiders like the jumping species and wolf spider, have developed infinitely better eyesight. Some have even speculated that the Salticidae genus have intelligence not unlike a cat.
 

Venom1080

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Tarantulas are the last spiders in the evolutionary line. True spiders, notably hunting spiders like the jumping species and wolf spider, have developed infinitely better eyesight. Some have even speculated that the Salticidae genus have intelligence not unlike a cat.
wouldnt that make tham the first in line? and im pretty sure trap door spiders are more primitive.
if you want to see a intelligent spider, look up the portia spider on youtube. it plans its attacks on other spiders.
 

KezyGLA

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Joking aside, when I walk into my T room most African sp. will dart for their hides before I can walk into the middle of the room and the big NW terrestrials will retreat when they feel me come into the room

I may get shot down for this but in my experience I feel I must say a few things.

The only Theraphosidae I have seen with what may be ' bad eyesight' is Grammys, Aphono, Brachy and Avic.

You can sometimes drop it right on their web right next to them, you think they arent hungry them go to remove but once you intervene with tongs they then know its there?

Over the years, whenever I have dropped prey they will usually put the front legs straight over prey, in what seems like a 'what is this, and can i eat it' effect.

Yet I am no spider man

Were whenever I have dropped prey into a baboon sp. enclosure it will disappear as soon as it moves on their web. As if they see it closing in. I have noticed thi with eastern Asian sp. too. It is almost like they watch it before you let go.

I have been experimenting with a few of the 'thele' species and they seem to not miss anything. You can be in the same spot away from the tank and move slightly then there is a burst of speed that seems to come from nowhere as tbe leg it around the emclosure without you having touch the thing.

Although I believe that there has got to be genus with bad eyesight out there, i dont think applys for all.

(Please excuse me it may not sound right, I tried to use google traductor for english)
 

Ungoliant

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Joking aside, when I walk into my T room most African sp. will dart for their hides before I can walk into the middle of the room and the big NW terrestrials will retreat when they feel me come into the room
They are extremely sensitive to vibrations, even ones you can't feel.
 

viper69

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I was curious how we know they can't "see" that well.
Scientists have studied their vision decades ago, I believe back in the 60s, certainly the 70s. If you google, you can find some scientific papers in peer-reviewed literature to read. We know what wavelengths of light they are sensitive to as well generally speaking.

I don't think they're indifferent to their surroundings in the least, they just "see" their world differently than we do
Are you speaking of vision? If so, this is not entirely true, their vision is not that great, scientific studies have proven this.

They sure can jump, so they must see where they're jumping?? Or do they just hope they'll hit a branch or sth?
I'm pretty certain there are no published studies of this type for tarantulas, for true spiders such as Jumpers there are! As it's obvious they are visual predators.

Some long time keepers of Ts have speculated based on observation that Pokis might have better eye sight than say a NW Brachy. I've certainly experience things that indicate this. I do not however have proof. What they see however I don't know.

I do "know" that Avics will jump off you without any knowledge of what is around them. You have to remember in the wild they EXPECT their to be branches and other things to break their fall to grab a hold of. They are not expecting to jump off of something, ie one's arm, and have no trees bushes etc around them.
 
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