Today we are going to show you a squid dissection.
If you are sensitive, please turn the video off now.
If not, I hope you enjoy.
This is a market squid, squids are a mollusk.
There are several different types of mollusks.
To name a few, there are bivalves, which include clams and mussels,
gastropods, which include abalone and snails,
and cephalopods, which include squids and octopuses.
Let’s break down the word cephalopod,
cephalo means head and pod means foot.
If you look at what appears to be the legs or the tentacles,
they look like they are connected directly to the head,
hence the name cephalopod.
There are a few physical differences between squids and octopuses.
You may already know that octopuses have eight arms;
squids have eight arms and two additional tentacles.
You can differentiate the arms and the tentacles, because the tentacles are longer.
They also don’t have any suction cups until you reach the end of the tentacle.
If you look closely, you can see the eight arms and one of the two tentacles,
unfortunately the other tentacle got broken off.
Another interesting fact is if you look at the mantle of the squid
or the long pointed part of the body,
they have tiny dots all over their mantle.
These are called chromatophores.
And these are tiny cells that contain pigment.
By having these cells, it allows the octopus and squid to change colors
and even aid in camouflage.
It is also believed that this may allow them to communicate with each other.
They do this by expanding and constricting these cells very rapidly
so they can change colors at a very fast rate.
They are visual communicators and we are verbal communicators.
If we look towards the tip of the mantle, it looks like there are two flaps at the end.
These are the fins of the squid.
These are not used for fast swimming;
these are more for staying in the same spot in the water column or for slow swimming.
When they want to swim fast in order to get away from a predator,
they’ll use something called a siphon.
We can see the siphon of the squid but we first have to turn it over.
If we look by the eyes you can see a flap of skin that looks like a tube,
this is the siphon.
In order to swim fast, they will fill their mantle full of water
and they have strong muscles and they will constrict these muscles
and it shoots the water out at a fast rate,
which enables the squid to swim very very fast.
This siphon has many other uses as well.
If the squid wanted to squirt ink, this is where the ink would come out.
This is also where they expel waste and reproductive gametes.
Now we will open up the squid to see the internal anatomy.
In order to get the best view, we have to make sure the squid is in the right position to open up.
Before we cut it open, the siphon needs to be up and the fins flat against the board.
Now just above the eyes and the siphon,
you will slightly pinch the sides together and you will see a little flap.
This is called the collar.
If you pop the collar, it makes it much easier to get the scissors in
and you get a nice clean cut without damaging any of the internal organs.
Now let’s cut up the mantle, starting at the collar all the way up to the pointed tip.
It may look like a blob or a mess inside
but we will learn what all of these internal organs are shortly.
But first, I’m going to open up the second one,
let’s see if we can see the difference between the two.
The one on the left has white in the middle of the body and clear near the top.
The one on the right doesn’t have the white in the middle but the white is more towards the top.
These are the gonads or the reproductive organs of the squid.
This tells me that the one on right is a male,
the white part are the testes
and the one on the left is a female.
The clear part of the female near the top are the ovaries
and the white part is called a nidamental gland.
This gland makes the gelatinous casing that holds the eggs.
Now let’s look for the similarities between the two.
If we look in the middle of the body,
we see a small organ that looks like a little flap.
There is one on each side of the body,
these are the gills.
Just like fish, they use their gills to help supply oxygen to their organs.
Now you may have noticed that there's a silvery or a black organ in the middle of its body.
You may have already guessed but this is the ink sac.
In females its slightly tucked under the nidamental gland, but we can still see it.
Squids will use their ink to get away from predators.
When they squirt it out, it looks like smoke in the water.
Not only does this act as visual distraction,
it also acts as an olfactory distraction.
The predator is unable to see the squid but it’s also unable to smell the squid.
Once the ink clears up, the squid is long gone.
Next, let’s look for the heart.
If we follow the gills up to where they meet in the middle,
we see a yellowish blob.
This is one of three hearts.
One is connected to each gill,
this is called a branchial heart
and there is one in the middle called a systemic heart.
Just like in people, the heart supply blood to the organs.
The branchial heart supplies blood to the gills
and the systemic heart supplies blood to the rest of the body.
Looking at this squid, do you see the blood?
Blood in squids is a little bit different than people.
Our blood is iron based,
which makes it bright red when it's oxygenated and dark red when it’s deoxygenated.
In squids, their blood is copper based,
which makes their blood clear when it's oxygenated and blue when it's deoxygenated.
Now let’s find the mouth of the squid.
Similar to the octopus, it’s in the middle of the arms.
If we fold back the arms, we see a black dot in the middle,
that is the mouth and the black part you see is their beak.
The way that squids eat is that they grab onto their prey with their tentacles,
and they use their beak to tear apart their food.
They also have a structure that is comparable to a tongue called a radula.
We will not be able to see the radula but we are able to remove the beak.
If you pinch tightly, the beak will pop right out.
If you look close, you can see that they are formed in a way that they fit perfectly together.
For the second squid, I tried to pop out the beak
but instead the entire structure including the surrounding muscles and even the esophagus came out.
Next, let’s take a look at the eye.
If you notice, the eyes are located on the side of the head
and they are considerable larger compared to the size of the head.
This is an evolutionary adaptation to allow it to see in low light and eliminate blind spots.
Also remember from earlier, squids are visual communicators
so it is important that they have great vision.
Let’s open up the eye and see if we can find the lens.
If you cut directly across the eye, some fluid will come out,
but if you feel around you will feel a tiny, hard round structure.
This is the lens of the eye.
Just like our eyes, the lens allows the squid to focus on objects.
Lastly, let’s look for the shell of the squid.
As we mentioned earlier, squids are a mollusk,
and they are soft bodied animals with a hard shell.
Most mollusk have hard external shells, but there are some species that have internal shells.
In the case of the squid, it has something called a reduced shell or a Gladius,
it helps support the mantle of the squid.
This is often referred to as the “pen” of the squid.
That concludes our squid dissection,
I hope you enjoyed it and learned something new.
Thanks for watching.