Just How Big Are The Eyes Of A Giant Squid?

http://www.npr.org/2012/03/15/148694025/just-how-big-are-the-eyes-of-a-giant-squid

by tokenadult • 14 years ago

62 12 14 years ago

npr.org

tokenadult• 14 years ago

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...

bootload2• 14 years ago

"... 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... 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... (400Mb @ 1hr+) and the highlights ~ http://museumvictoria.com.au/learning-federation/video-temp/... (10min)

balsam• 14 years ago

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.)

bootload2• 14 years ago

"... 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.

mokus• 14 years ago

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• 14 years ago

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• 14 years ago

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.?

ginko• 14 years ago

The reason is that a larger retina with a larger aperture is able to detect more photons because of its larger area.

This makes them more effective at seeing in the darkness of the deep ocean.

It's the same reason why cameras with full-size sensors are more light-sensitive and create higher quality images.

nsomaru• 14 years ago

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

;)

TeMPOraL• 14 years ago

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• 14 years ago

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

sebkomianos• 14 years ago

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.

Just How Big Are The Eyes Of A Giant Squid?

Related Stories