The benefit of eight eyes

[dragonblade71]

For quite a while, Ive been wondering why most spiders have so many eyes (usually eight.) Considering that most spiders have very poor eye sight, you do have to wonder what is the point of having a large number of eyes if they can't really see that well. I could see some benefit of having so many eyes if they were spaced well apart around the head - giving a super wide field of view (like with jumping spiders.) Another animal that comes to mind are dogs (having eyes on the opposite sides of their head to provide a wider view of their surroundings.) Though most spiders have eyes that are very close together which to me, doesn't seem like a great benefit (like they're not being utilised effectively.)

 

[The Snark]

A man I used to work for with a PhD in optometrics would be best suited to answer that. But coming from an electronics background I can toss a little out.
Sophisticated rods and cones, a focal lens with a variable light aperture attached to a complex neural matrix is but one application of the use of wavelength detection and reception.
A quick check in the electronics field turns up around 1200 common devices in or near the visible light spectrum with different applications. No doubt there are many thousands more. One needs to think outside the box of human eyesight. From simple motion detectors through stereoscopic (or maybe quadrascopic) distance measurements on out to the Webb telescope which can't detect enough visible light to negotiate it's way across a room.
Then you can couple that with the neurons in the brain that operate the vision capability. From literally a few simple motion detection neurons that augments the setae on a spiders legs on out to salticids with over half of the brain cavity utilized and connected to the two major eyes.

Consider the spider evolution. A product of it's environment over tens of thousands of eons each iteration contributing some slightly different factor in it's spacial detection. Eight seems to be the optimal array of eyes with exceptions where that many weren't required in the environment it evolved in. Other eyes are useless and nearly or totally abandoned as the environment varied. Latrodecutus is suspected of being near completely blind with an eyesight detection range of possibly as little as 1 cm. It switched to an entirely different set of senses.

And lastly, a completely uncharted territory. Neurons that act as photo multipliers and filters as we use various electronic devices. Think of the permutations or augmentations that take a multiplex electronic signal and turn it into a high res 3D image on a wide screen HD display,

 

[viper69]

For quite a while, Ive been wondering why most spiders have so many eyes (usually eight.) Considering that most spiders have very poor eye sight, you do have to wonder what is the point of having a large number of eyes if they can't really see that well. I could see some benefit of having so many eyes if they were spaced well apart around the head - giving a super wide field of view (like with jumping spiders.) Another animal that comes to mind are dogs (having eyes on the opposite sides of their head to provide a wider view of their surroundings.) Though most spiders have eyes that are very close together which to me, doesn't seem like a great benefit (like they're not being utilised effectively.)

If you read literature on jumpers you’ll come across some ideas on this. Had a faculty friend who used jumpers for vision research.

also generally animals with eyes on side of head do have wider field of view- because they are prey

 

[Ultum4Spiderz]

If you read literature on jumpers you’ll come across some ideas on this. Had a faculty friend who used jumpers for vision research.

also generally animals with eyes on side of head do have wider field of view- because they are prey

Yeah jumpers got spectacular eye sight for a spider !! Crazy how small rodents grow quicker than my roaches .. yes eyes on side of head like prey but they must be a good sized threat especially rats to wild arachnids? Especially when urticating hairs are meant for them.
Seems arboreal Ts have better ability to see shadows and stuff then terrestrials but-have many study’s if any been done ??

 

[viper69]

Yeah jumpers got spectacular eye sight for a spider !! Crazy how small rodents grow quicker than my roaches .. yes eyes on side of head like prey but they must be a good sized threat especially rats to wild arachnids? Especially when urticating hairs are meant for them.
Seems arboreal Ts have better ability to see shadows and stuff then terrestrials but-have many study’s if any been done ??

For tarantula vision from keepers it's all anecdotal of course. Some of keepers of OW arboreals seem to think Pokis for example have better vision- based on some observations- than say Brachy's but honestly it's guess work.

 

[The Snark]

And then, if there was some way to measure the visual acuity and sensitivity of the various arachnids, there would be differences between animals of the same species in perception and utilization. Compare the theoretical ultimate Sherlock Holmes acutely trained observer on out to people who fail to pay attention to their surroundings and fall off cliffs or into open sewer drains. And spatial awareness can easily skew whatever measurements that are proven repeatable and predictable, varying from animal to animal..

Spatial contextual awareness - Wikipedia

en.wikipedia.org

Spatial ability - Wikipedia

en.wikipedia.org

 

[Ultum4Spiderz]

And then, if there was some way to measure the visual acuity and sensitivity of the various arachnids, there would be differences between animals of the same species in perception and utilization. Compare the theoretical ultimate Sherlock Holmes acutely trained observer on out to people who fail to pay attention to their surroundings and fall off cliffs or into open sewer drains. And spatial awareness can easily skew whatever measurements that are proven repeatable and predictable, varying from animal to animal..

Spatial contextual awareness - Wikipedia

en.wikipedia.org

Spatial ability - Wikipedia

en.wikipedia.org

Even sadder some of these people falling into deadly, dangerous spots often are too busy taking selfies to notice any danger .. or Even crazier those freee mountain climbers I watched a Netflix documentary on one of the best of those climbers ..
spiders got terrible eyesight mostly but avoid danger in way other species fail too and often can sense predators too. Although not always..
Centipedes and Pepsis wasps are a nightmare.

 

[viper69]

Even sadder some of these people falling into deadly, dangerous spots often are too busy taking selfies to notice any danger .. or Even crazier those freee mountain climbers I watched a Netflix documentary on one of the best of those climbers ..
spiders got terrible eyesight mostly but avoid danger in way other species fail too and often can sense predators too. Although not always..
Centipedes and Pepsis wasps are a nightmare.

It’s Darwinism at work- I never feel bad for them

And the free climbers know the risks!

 

[The Snark]

people falling into deadly, dangerous spots often are too busy taking selfies to notice any danger

Selfies are but the latest distractions in a very long list. Welcome to the world of stupid moves and emergency services.

spiders got terrible eyesight mostly but avoid danger in way

The setae of some spiders exceeds the spatial awareness that humans possess

 

[dragonblade71]

also generally animals with eyes on side of head do have wider field of view- because they are prey

Yes, generally true. I watched an insightful David Attenborough documentary about that. Interesting that dogs are an exception to the predator rule with the usual forward facing eyes.

 

[The Snark]

or Even crazier those freee mountain climbers I watched a Netflix documentary on one of the best of those climbers

Groom steps back for wedding photo, falls 90 feet to his death
Naked couple arrives at fire hall. Their vehicle rolled off a cliff while they were busy.
Engine fire. Drives vehicle into lake. Drowns.
Cleaning tar off floor with gasoline next to a gas water heater. Fire department parlance: crispy critter.
And many many more.
Cell phones, small change. Practice spatial awareness and evaluate consequences, which spiders do automatically in many or most environments.

 

[viper69]

Yes, generally true. I watched an insightful David Attenborough documentary about that. Interesting that dogs are an exception to the predator rule with the usual forward facing eyes.

As I always say about nature - always exceptions, and in my original reply my use of “generally”

 

[dragonblade71]

It is impressive how well most spiders can sense both prey and danger through their other senses. Once in the wild, I observed a trapdoor spider who popped out of a burrow as soon as a fly landed nearby. And there wasn't even any silk lines running from that burrow.

I know of three spiders that do have good vision - jumping spiders, wolf spiders and net casting spiders. And one physical characteristic which those three spiders share is two large forward facing eyes (with the other eyes being significantly smaller.) So having two larges eyes seems to be a somewhat reliable indicator of good vision in a spider.

 

[Ultum4Spiderz]

As I always say about nature - always exceptions, and in my original reply my use of “generally”

Dog is just a domesticated breed of wolf they aren’t not predators. our Huskys would destroy any rabbits or animals that happened to wander in our fence . Rip miss those dogs .. neighbor cats weren’t a fan … especially the one time they got loose.

Yes, generally true. I watched an insightful David Attenborough documentary about that. Interesting that dogs are an exception to the predator rule with the usual forward facing eyes.

What specifically did he say about dogs not being predators? Besides that? Lol .. man’s best friend has wolf like teeth nearly just smaller ! It Ain’t no herbivore although they been domesticated for ages so can eat most humans food.

 

[dragonblade71]

What specifically did he say about dogs not being predators? Besides that? Lol .. man’s best friend has shark teeth! It Ain’t no herbivore although they been domesticated for ages so can eat most humans food.

He was using big cats as an example and the prey that they generally chase (and the difference in eye placement between those two types of animals.) I do maintain the belief that wolves are predators. Despite them having eyes on the sides of the head.

 

[viper69]

Dog is just a domesticated breed of wolf they aren’t not predators. our Huskys would destroy any rabbits or animals that happened to wander in our fence . Rip miss those dogs .. neighbor cats weren’t a fan … especially the one time they got loose.

What specifically did he say about dogs not being predators? Besides that? Lol .. man’s best friend has wolf like teeth nearly just smaller ! It Ain’t no herbivore although they been domesticated for ages so can eat most humans food.

I never said they weren't predators. Where in all my posts have I written "dogs are not predators"

What specifically did he say about dogs not being predators?

I didn't ever mention dogs.

He was using big cats as an example

I never once mentioned big cats



In point of fact I never mentioned any specific animal scroll up people

You guys are crazy

 

[dragonblade71]

I never once mentioned big cats

David Attenborough was using big cats as an example in the documentary that I was watching on TV. That's who I was referring to, not you.

 

[The Snark]

Sideways facing eyes are normally reserved for herbivores that require greater peripheral vision to avoid omnivores and carnivores. With certain exceptions such as many spider species.

 

[viper69]

David Attenborough was using big cats as an example in the documentary that I was watching on TV. That's who I was referring to, not you.

Thanks for clarification! His shows are great.

 

[SpookySpooder]

What's the point of 8 eyes if you can't see the dubia playing dead right in front of you?



Who even needs eyes?!