

Just How Big Are The Eyes Of A Giant Squid? - tokenadult
http://www.npr.org/2012/03/15/148694025/just-how-big-are-the-eyes-of-a-giant-squid

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bootload
_"... Scientists didn't even have photographs of a live one in the wild until
2004. Occasionally, a fishing boat will haul in a big dead or dying blob.
..."_

Back in 2008 I watched a giant squid dissection & captured images of the
dissection ~
[http://www.flickr.com/photos/bootload/sets/72157606211764544...](http://www.flickr.com/photos/bootload/sets/72157606211764544/with/2676995608/)
But I don't remember viewing the eye. If memory serves me I think the eye was
a casualty of the ascent.

 _"... There's things down there where their entire bodies are made of snot,
they've got detachable heads, their teeth fall out, they explode and they eat
their snot jackets. ... There is just weird things going on everywhere. ..."_
Dr Mark Norman.

It was caught at a depth of 550m by a commercial fishing vessel, 'Zeehaan' off
the coast of Portland, Victoria. Weighing in at ~245Kg with a length of 12m
the dissection concentrated on finding things out like the length, contents of
the stomach, sex & also looking for sperm capsules injected by male squid at
speed. The place stank of ammonium and no you couldn't eat it. The flesh is
infused with ammonia for buoyancy.

There is also a video of the entire dissection & running commentary by _"Squid
(Cephalopod) nerd"_ , Dr Mark Norman from Museum of Victoria ~
[http://museumvictoria.com.au/pages/7003/MVLiveSquidDissectio...](http://museumvictoria.com.au/pages/7003/MVLiveSquidDissection.wmv)
(400Mb @ 1hr+) and the highlights ~ [http://museumvictoria.com.au/learning-
federation/video-temp/...](http://museumvictoria.com.au/learning-
federation/video-temp/public-dissection-of-giant-squid-video/) (10min)

~~~
balsam
Anecdotally we once had a dish of raw squid at a Japanese restaurant. They
tried to dissuade us from ordering it. I could taste nothing but ammonia.
There's also the ammonia (aka Liquorice?) flavored vodka:
<http://en.wikipedia.org/wiki/Salmiakki_Koskenkorva>

Take home: what is edible may depend on where you grew up (deep ocean, etc.)

~~~
bootload
_"... They tried to dissuade us from ordering it. I could taste nothing but
ammonia. ..."_

That is funny, don't say they didn't warn you. The room I was in was pretty
big, 2 levels but the smell was like putting your nose to bleach. The taste
doesn't seem to matter to Sperm whale.

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tokenadult
BBC report with animal size comparison charts:

<http://www.bbc.co.uk/news/science-environment-17365736>

Link to abstract of article in Current Biology that is prompting the press
reports:

[http://www.sciencedirect.com/science/article/pii/S0960982212...](http://www.sciencedirect.com/science/article/pii/S0960982212001820)

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mokus
How does the "large eye to see large objects" thesis make any sense at all? I
can see the moon just fine with my puny little orbs. I get that the large eye
will have an extremely narrow "depth of field" for small objects, but how does
that mean it will see larger ones any better?

It seems a whole lot more likely to me that it's "large eye to catch more
photons because it's _DARK_ down there".

EDIT: maybe something to do with the fact that the light that is down there
falls off quickly so a larger aperture somehow lets you correlate the
scattered light better?

~~~
palish
The simple answer is: the larger the eye, the more "pixels" (cells of the
retina which respond to light energy). So larger eye == higher resolution.

The current theory regarding "why is all that resolution necessary?" is: there
are tiny creatures swimming alongside the squid, which respond to a sperm
whale's sonar by emitting a tiny amount of light. When the squid sees this
light, it knows that a whale attack is imminent, and runs. (Well, jets.)

If the eyes were smaller then there wouldn't be enough resolution to make out
the tiny dots of light emitted by those tiny creatures.

Another way of thinking about it is: the eye needed to evolve larger in
proportion to how tiny the creature is. If the creatures were twice as big,
then the eye would've evolved half as large as it currently is. (If the theory
is true.)

Mathematically, there need to be enough retina cells such that "1 tiny
creature at distance D can be detected per degree of viewing angle". E.g. if
the squid has a 130deg field of view, and it needs to be able to see the
creature light up within 1 foot of its eye, then it needs enough retina cells
in order to scan the entire conic volume of the space between the eye point
and "1 foot in front of the eye point". By the Nyquist frequency, that
suggests there need to be at least two retina cells per "tiny creature body
length projected from a distance of 1 foot". (The farther it is from the eye,
the smaller its projection; and thus correspondingly more retina cells are
required, which requires a physically larger eyeball. Note that as the eye
gets larger, the field of view remains the same.)

To clarify: the squid isn't looking at the whale at all. Rather, the squid is
looking at tiny sea creatures very close to its face that light up when hit by
a whale's sonar. Thus they act as an early warning system for the squid.

~~~
mhb
The squid doesn't need to resolve the little sea creatures in order to detect
a whale. It only needs enough resolution to resolve a huge number of the
little lights into a whale-shaped blob. For that, it needs an eye with the
biggest possible aperture and sensitive sensors. The increased resolution may
be an additional benefit of the better light-gathering ability of a big eye
but isn't necessary.

The article says _the researchers calculate that the squid eyes they measured
are the optimal size for seeing something far away and massive_. Why isn't the
biggest possible eye that can be grown the best? Is there some other
constraint besides the mechanical structural issue or risk of damage, etc.?

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TeMPOraL
I'd wish there would be a browser extension that would find all the occurences
of numbers with imperial units (like "40 feet" or "10 miles") and offered a
metric conversion as a hovertext, or whatever. Just like this dumb, annoying
Skype extension that converts everything that looks like a phone number to
Call-By-Skype button, but without the dumb & annoying part.

It's hard for me, as well as probably for the majority of this planet, to
easily visualize what the article is about, when everything is given in alien
units (and constant CTRL+TABing to Wolfram|Alpha kind of breaks the reading
flow).

~~~
ranit8
I wish American teachers would follow the advice given by The Oatmeal:
<http://theoatmeal.com/pl/senior_year/science>

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sebkomianos
It's eye looks like the eye Argonauts used to draw on their ships. I am
posting a link to an image when I find one.

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nsomaru
I wonder if eyes like that would help you spot bugs easier

;)

