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Commerson's dolphins have acute vision both in and out of the water.
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| 2. |
The lens of a marine mammal's eye is stronger than that of a land mammal. |
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In the eye of a land mammal, the cornea focuses light rays toward the lens, which further focuses the light rays onto the retina. Underwater, the cornea isn't able to adequately focus waves into the lens because the refractive index of water is similar to that of the interior of the eye.
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The eye of a marine mammal compensates for this lack of refraction at the cornea interface by having a much stronger, spherical lens. It is more similar to the lens of a fish's eye than the lens of a land mammal's eye. |
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In air, a marine mammal's eye compensates for the added refraction at the air-cornea interface. At least in bright light, constricting the pupil helps, but it doesn't fully explain how a whale achieves visual acuity in air. Research is ongoing. |
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| 3. |
DNA from several other species of toothed whales indicated that the eyes of these whales do not develop pigment cells called "S-cones," which are sensitive to blue light. Researchers theorize that all modern cetaceans lack these visual pigments and therefore aren't able to discriminate color in the blue wavelengths. |
