They have a squid (http://news.yahoo.com/s/ap/20080430/ap_on_re_as/new_zealand_colossal_squid;_ylt=AuRwVLOkuQK83jJ6q7 vemDwPLBIF)with eyes the size of soccer balls. Why does it need eyes so large in comparison to the rest of its body? I know its to see better at deep dark depths, but why can't it just have small really good eyes, like a cat?

Architeuthis is equipped with the largest eyes in the animal kingdom. A number of vertebrate animals are larger than Architeuthis, yet none have eyes of comparable size. At 25 cm in diameter, the eyes of Architeuthis are the size of a human head! Cephalopods are visual animals and are distinguished among invertebrates for their highly complex visual system.

The visual systems of cephalopods and vertebrates are an example of convergent evolution. This means both groups of animals see alike, but their ability to see evolved separately in each group. In fact, if we compare squid eyes to our own, we find remarkable similarity in the anatomy. Squid and people both have eyes with single lenses, pupils, irises and retinas. We can only guess at the light sensing capabilities of an eye with such an enormous retina

http://www.dogpile.com/clickserver/_iceUrlFlag=1?rawURL=http%3A%2F%2Fwww.mnh.si.edu%2 Fnatural_partners%2Fsquid4%2FArchiteuthisAdaptatio ns.html&0=&1=0&4=204.9.89.53&5=65.9.132.52&9=e6433707ed28486bbf3b67ce8faac801&10=1&11=info.dogpl&13=search&14=239137&15=main-title&17=13&18=2&19=0&20=2&21=11&22=i6LAxbgvm%2Bs%3D&23=0&40=dMYPiPnbJzw7BR7%2BOleINA%3D%3D&_IceUrl=true

so its the retina that needs to be bigger, not the lens or the pupil? Why can't they just have a extra large retina in a small eye?

so its the retina that needs to be bigger, not the lens or the pupil? Why can't they just have a extra large retina in a small eye?

Wouldn't be the same, I don't think it would fit.

couldn't it just take up more of the back of the eye?

I think a bigger lens would gather more light, in addition to needing a large retina area. It must be very dark down there.

A bigger pupil to let in as much light as possible, I believe. But who knows?

Orleander, the answer is in the article you quoted.
"It has a huge lens the size of an orange and captures an awful lot of light in the dark depths in which it hunts."

Isn't a cat capable of seeing in absolute dark? why doesn't it just have eyes similar to the cats eyes then. I think that's what orleander was asking too.

Isn't a cat capable of seeing in absolute dark? why doesn't it just have eyes similar to the cats eyes then. I think that's what orleander was asking too.

Well first of all, no creatures can see in absolute dark.
Cats make use of moonlight, squids can't.
And not many wavelengths penetrate far beneath the surface.
Red light is absorbed first, then orange, yellow, green etc.
Blue light penetrates the furthest.
So water absorbs diffent wavelengths of light at different depths, this had an impact on how squid eyes evolved.

In short, cats and squids life in completely different environments regarding light. You can't compare them.
A squids eye-size is the result of it's environment. If it could have evolved the same effectiveness while staying small, it would have. Eyes, and associated brain-activity, consumes huge amounts of energy.

you're right I'm being stupid, you always need some kind of light or sound to see. So what's different about the moons light that makes it so that we can't see it but cats can? Well we can but not as effectively as cats apparently.

you're right I'm being stupid, you always need some kind of light or sound to see. So what's different about the moons light that makes it so that we can't see it but cats can? Well we can but not as effectively as cats apparently.

Cats have a reflective layer behind the retina. So the light that enters their eyes hits the retina, then reflects back and hits the retina again. This is way they can see so much better in dark conditions.
You might have heard about or seen eyeshine in cats or other animals, this is caused by the light reflecting back out of their eyes.
This makes them see better at night but impairs their vision in day light somewhat.
In addition they have far more rods (and fewer cones) than we have, again enhancing night vision.

Btw. why isn't this in Biology ??

For any given technology: larger size improves resolution, light gathering capacity, and chromatic aberration performance, in an optical sensing device.

The control is the necessity of paying for, constructing, and supporting (in all ways) the enlarging device. Costs increase faster than performance gain, after a certain "sweet spot".

Cats probably would have much larger eyes, if there were no increasing price to be paid for them. Apparently either the costs are much lower or the payoffs are much higher for a squid in the middle of the ocean.

and the whales that eat them don't have large eyes because they have echo location and don't need large eyes..right?

and the whales that eat them don't have large eyes because they have echo location and don't need large eyes..right?

Right.

so why are somethings that live in darkness blind?

so why are somethings that live in darkness blind?

Because they can get by without eyes. It saves energy if you can.

so why are somethings that live in darkness blind?

They use a different sensory system

what? whiskers?

what? whiskers?

Antennae.

what? whiskers?

Possibly but I think they also make use of an extra-sensitive lateral line.

lateral line??

lateral line??

I am no expert but I know that fish can detect changes in pressure because of a line running the the length of the body on each side. Lateral = side

Bottom feeders such as cod have whiskers ( I'm not sure what the technical name is ) which allow them to sense food . Next time you see a cod look at its lower lip.

I've never seen a cod. Lots of catfish and carp, but never a cod.

Large eyes are not a usual adaptation to low light conditions.
You don't need them.
Our own eyes can react to a single photon.

Large lenses are used for
seeing great distances
magnifying objects
seeing at a very wide angle.

I can't think why this squid has them.

Since they have such a huge predator coming at them (whales, other squid) maybe it has nothing to do with light, but with being able to see in all directions.

The more rods you have the better you can see in low light conditions. The same goes for murky water.

so an animal can have huge eyes with few rods and a small eye with bunches of rods, can't it??

so an animal can have huge eyes with few rods and a small eye with bunches of rods, can't it??

In theory, yes. But there will have to a good reason for it.

do you need rods to see movement?

do you need rods to see movement?

Rods are for detecting brightness, dark/light.
Cones are for detecting colors.
You need a brain to detect movement.

Rods are for detecting lightness, dark/light.
Cones are for detecting colors.
You need a brain to detect movement.

not eyes?

not eyes?

Of course, eyes too.

and if you had no brain you would never be able to detect movement, no matter how big your eyes were?

and if you had no brain you would never be able to detect movement, no matter how big your eyes were?

What is your point ?

What is your point ?

Thank you for posting.

Does anyone know? If you had no brain, but have eyes, can you detect movement?

That wasn't your question. You asked "do you need rods to see movement?"

You don't, if you still have cones..

If you had no brain, but have eyes, can you detect movement?

Well can you ?

I've had no luck trying to find the dimensions of a cachalot's eyes.

We know they are adapted to hunt squid by sonar, and the eyes appear small - but that's in comparison to the head, which is huge.

The closest I came was an estimate for a right whale, which is in the same size range but a much different animal - eyes about the size of an orange, was the comment.

edit: found one http://mysite.du.edu/~ttyler/ploughboy/bealenew.htm#EYE about 2 1/2 inches in diameter, in a female (they are smaller).

According to all accounts, the eyes of a cachalot are very mobile - unlike msot fish, say. But they cannot deliver binocular vision, being on either side of a head the size of a small bus.

so sperm whales are going down there mostly blind and just getting them by echo location. As many squid as they eat, it must be a huge advantage over having eyes.

A five centimeter eye is a damn big one. A cachalot is hardly blind.

But there is essentially no light from the sun at those depths. So the whale finds sonar useful for the same reasons a bat does, at least. And probably much more - a whale's ear is fantastically capable, with many times the range of a human (humans hear pretty well, actually) and operating under pressure changes that would implode your sinuses.

Mammals in general hear better than other kinds of beings - better than birds, much better than fish or amphibians. They have more complex ear structures. And whales hear better than other mammals.

And they are very vocal. They sing and stuff.

do only mammals have the ability to echo locate?