Amazing: sight on land and sea

Have you ever opened your eyes underwater?

Its not that you can’t see, but certainly that you can’t see CLEARLY. And definitely not clearly enough to hunt.  How do sea lions and other marine mammals do it?

Multi talented

Multi talented

Well, it’s definitely multiple factors.  Firstly, their eyes are proportionally larger than our eyes, so they are able to absorb more light underwater.  They also have increased light sensitivity, which is traded for color sensitivity.  Its believed that they can see colors on the blue and green spectrum, but with increased light sensitivity they can get more light underwater.

big eyes

big eyes

Secondly, they have a transparent THIRD eyelid! Here’s your word for the day: nictitating membrane.  Many animals have this third transparent eye lid when they live in diverse or adverse conditions.  Camels have this to protect their eyes from sand, and many marine mammals have it to protect and see underwater.  Except in the case of sea lions, their natural eye is what they use underwater: they use their nictitating membrane on land to protect  from sun and sand.

a blue shark closing its nictitating membrane.

a blue shark closing its nictitating membrane.

Unlike the upper and lower eye lids you have, these eyelids move horizontally across the eye.

Thirdly, their eyes are set in a cushion of fat, which offers a pillow for the eyes when our favorite “ocean dogs” dive and the pressure becomes great.

We have found ways to adapt to their underwater world, but sea lions and seals are naturally set! Amazing! Perhaps we should take a note from them in future scuba diving gear innovation.

This sweet moment was captured at the Pacific Marine Mammal Center

This sweet moment was captured at the Pacific Marine Mammal Center

xmerbabe

Other animals with nictitating membrane:

Polar bears (to protect from snow blindness)

Sharks (protection from prey who object to being eaten)

Beavers: to protect WHILE diving

Eagles: to protect their eyes while feeding chicks

Cats (and dogs) because cats are the boss of you and can do whatever the hell they want, include have third eyelids.

her true self: always with her nictitating membrane

her true self: always with her nictitating membrane

 

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s