My question: how do aquatic mammals handle this? Seals, for example, hunt fish and so should need good vision underwater, but I myself saw a trained seal, with its head above water, open its mouth and yell when its trainer opened his mouth, which seems to indicate that seals have good vision out of water as well. Do their eyes compensate for the changed index somehow, much like how human eyes adapt to light and dark conditions by regulating the size of the pupil?
This is a bit of a WAG, but I seem to recall that aquatic mammals have something called a “nictitating membrane” (I know frogs have one) which is a clear eyelid that slides down over the eyeball when the mammal goes underwater. Presumably this eyelid has a consistency such that it compensates for the difference in light refraction and allows the animal to see clearly underwater.
I think we featherless bipeds are the odd men out when it comes to the nictatating membrane. However, I’m not sure how this would help aquatic mammals.
Here’s a vague, general answer from another Dr. Phil.
Damnit, Jim, I’m a physicist, not a zoölogist! In other words, I don’t have any idea specifically what mechanisms semiaquatic mammals use to compensate.
Nictitating membranes conform to the shape of the eye and are ften translucent. To tell the truth, I don’t think that they can explain how seals, etc. can see well underwater. My guess would be that they can accommodate really well, maybe by using the crystalline lens (we use it, but ony for fine-tuning. By far, most of the “ray bending” takes place at the cornea-air interface). I’ll have to look into this.
By the way, you can see well underwater if you wear appropriate glasses. Not goggles or a face mask (although those will work, too, of course), but specially-made glasses that compensate for the loss of power at the cornea-air interfce when it becomes a cornes-water interface. I’ve got a file on these devices. They nver seem to have caught on as a consumer item.
My understanding is that aquatic mammals have a more spherical lens to deal with the difference in light refractive quality underwater. The result is they would probably tend to be a bit myopic when above water. Cetaceans at least can apparently compensate somewhat by using powerful ocular muscles that can adjust the shape of the lens as needed. Don’t know if any of the other aquatic mammals can do the same.
By and large marine mammals tend to have poor to nonexistant color-vision.
Off topic, I suppose, but why do you think he typed it accidentally? In English, an o (or e or whatever) with dots over it is a diaresis and it tells you to pronounce a vowel that would otherwise be combined with another vowel sound or silent. My daughter’s name is Zoë, pronounced Zoey, or naïve, Brontë, coöperate, and, of course zoölology. New Yorker magazine uses it all the time.
You’re kidding? It’s correct to write zoölogy? I’ve never seen it done before. I am of course familiar with Zoë, naïve, Brontë, Eloïse, Hawaï (I’ve seen it) and so on.
The New Yorker uses it all over the place. I think it may be OK to use wherever you want to break up two vowels into separate sounds. I’ve seen reëmployment, for example. Hawaï seems like a stretch to me. I suppose you could use it for noöne too.
Actually, I notice now that I wrote zoölology – which is wrong (or is it the study of the study of zoölogy?). Apparently, zoölogy is pronouce zoe-ology, not zoo-ology, so the ö is particularly apt.
And for the record, I typed it by hitting option-u, followed by an o. On a Mac, option-u means “put an umlaut on top of the next letter”. I don’t think that the computer makes a distinction between an umlaut and a diaresis.
They’re German and Greek names for the same thing. (Indeed, “diaresis” is the more correct name in English; “umlaut” is better reserved for the phonological phenomenon of that name.)
On Windows, if you modify your keyboard setting to “US-International” you can get an Umlaut such as ü by typing " followed by the vowel…ä, ö, ü, ë, ï, etc…
And, of course, if you’re using a Hebrew keyboard, you start seeing all kinds of Hebrew letteres instead of diaresis-capped vowels. Aren’t there Unicode equivalents (e.g. use “&+#+0+2+4+6+;” for ö ) for all these (well, hopefully soon-to-be) obsolete Latin-1 constructs?