Eye of a squid!!

Feb 16, 2015 • 10:21 PM UTC

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Microorganisms

Manu Prakash

I am a faculty at Stanford and run the Prakash Lab at Department of Bioengineering at Stanford University. Foldscope community is at the heart of our Frugal Science movement - and I can not tell you how proud I am of this community and grassroots movement. Find our work here: http://prakashlab.stanford.edu

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Life in the ocean is tough. You swim around to find food and if you are big; you don’t really have a place to hide. So you better watch out if you want to avoid danger in the open ocean. This is where sophisticated eyes come in to play. This post is about a very strange lens in the eye of a Squid. Yummy..
I got access to a humbolt squid recently (jumbo squid – pretty big guys) – you can get access to one of these by finding one in the ocean or through the “Squid for Kids” program. Thanks Hannah and William at Hopkins Marine station.
Firstly, I will describe its eye. I was surprised to notice that the eye was very hard. That was shocking I me since I had always thought that eyes are soft. Long time ago; Maxwell had noticed something really strange about eyes of a fish; which is – that the refractive index of the spherical lens in the eye of a fish changes as a distance from the center. This is termed as Gradient Index Lens (GRIN lens). He understood that this allows for reducing the lateral spherical and chromatic aberration.
Since, I had access to the eye of a dead squid – I took a small knife and peeled off small piece and put it in Foldscope. I should be very clear; I had access to a dead squid; so if I was not going to look at it – it’s sacrifice to science actually goes to waste.
Cheers
Manu