Eye Size

Orleander said:
lateral line??
Click to expand...

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.
 
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??
 
and if you had no brain you would never be able to detect movement, no matter how big your eyes were?
 
That wasn't your question. You asked "do you need rods to see movement?"

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