One of the first views of the enormous eye of the colossal squid. The eyeball is about 27 cm in diameter, around the size of a soccer ball, with a smaller opening. Vision is very important to colossal squid. They use their eyes to see and catch prey, to watch for predators, and to see each other. With huge eyes and built-in headlights, the squid is well equipped for life in the dark depths of the Southern Ocean. The colossal squid's eyes are placed so they face forward, giving the squid binocular, or stereoscopic, vision.
The giant squid, in contrast, has eyes placed on each side of the head. It can see forwards and behind to detect predators, but does not have the binocular vision needed to judge distances. The eyes of cephalopods squid and octopus , like those of the colossal squid are very like vertebrate 'camera eyes'. They contain a single lens that focuses images onto a retina lining the concave rear surface of the eye.
The team examining the colossal squid removed the lens from one eye. This lens is now on display in the exhibition on the interactive table. The other eye of the colossal squid was damaged. As in all cephalopods, the lens is in two pieces — two parts of a single lens. The lens is spherical and mm diameter, about the same size as an orange. During the dissection of the smaller colossal squid, the scientists examined the eye and the optic lobe.
This is the part of the squid's brain that processes the visual information coming from the eye. The optic lobe of the smaller colossal squid was the size of a small sausage. This is larger than the entire visual cortex of a human the visual cortex is our 'optic lobe' , and shows how important vision is to these huge squid.
It turns out they are named instead for the most prominent anatomical difference between them: the presence in myopsids or the absence in oegopsids of a cornea. Linguistic detour: Myopsida obviously comes from the same root as myopia , meaning "shut-eye" but the internet is not providing me with the etymology of Oegopsida. I would love any leads! The cornea is a transparent membrane over the lens of myopsid squid. It satisfies all their eye-covering needs, so they don't have actual eyelids although sometimes people refer to the cornea as an eyelid for extra confusion.
Oegopsid squid have no cornea, and consequently, their lenses are fully exposed to seawater. Most of the time they seem to be okay with that, but when scientists poke their eyes or perhaps in other threatening situations , they'd like to be able to cover up.
For that purpose, they have real eyelids made out of real skin. Here's an Ommastrephes bartramii winking at you. My inspiration for this post was a truly, truly weird squid news hit: Some commercials are stranger than others.
Most foreign commercials are strange because, well, they're foreign. This commercial's strange because a squid climbs out of a guys mouth and a piece of gum makes it disappear.
Just watch. I was compelled to ignore the yucky marketing message of "chew our gum so you can cheat with impunity" and consider this commerical with my biologist hat on. It's not easy, being a cephalopodiatrist! You get these compulsions! Do you want to know what it's like? Do you want to be a real squid nerd? Are squid just as smart? Unfortunately, it's much more difficult to study intelligence in squid, because they're more difficult to keep in the laboratory.
Octopuses live naturally in dens on the seafloor, an environment that is fairly easy to recreate in an aquarium, but most squids live naturally in the open ocean and need a great deal of space to move around.
Furthermore, since octopuses are used to crawling on the ground and manipulating shells and rocks, it's easy to give them mazes and puzzles to solve.
A dissection allows you to take a very close look at the nervous system of a squid, asking and answering questions about how it might work. Let's start with the brain, which comes in three parts: two optic lobes and a central ganglion. If you very carefully pull the eyes out of their sockets, you'll see the optic lobes, one behind each eye. They are yellowish white, soft and fleshy.
Between them in the middle of the head, and somewhat more difficult to identify, is the central ganglion, a collection of very soft nerve tissue that actually surrounds the esophagus--every bite the squid takes goes through its brain!
As you cut into the head of a Humboldt squid, you'll notice that the brain is protected by a tough braincase that looks like it's made of cartilage.
It's not proper cartilage like humans have, but it's a similar protein. When scientists use sonar to detect squid in the water, this braincase is one of the major parts of the body that reflects the sound. Don't forget to look at the eyes themselves. On the side facing out, you can see the clear lens, which works just like the lens in our eyes, to focus light. It's quite hard, though it is only made of protein and you can dig into it with a fingernail. If the lens is in very good condition, you can actually place it over text and use it as a magnifier.
On the eyeball all around the lens, you can see a reflective mirror-like coating. That's part of the squid's camouflage. Its eyes are very large and easy to see, so it tries to hide them from predators by reflecting light away from them.
But it also needs some light to see, so it can't reflect all the light. Now look at the back of the eye after you've pulled it out of the eye socket.
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