have you ever thought about exactly what
goes on in the minds of our fish how do
they work out where the pellet of food
is so accurately how do they learn you
know who feeds them and they come to the
glass and greet you and beg for treats
when you walk up well when compared to
fish cephalopods like cuttlefish are
even more impressive they can solve
puzzles they you know they use their
tentacles to reach out and grab the food
at lightning speed and you know both
themselves and their food is moving in
3d space so how does that work hi guys
and girls I'm weave men and this video
is all about cuttlefish vision take a
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if you're not then welcome back instead
to see again you probably know that we
have you know two eyes and then if you
were to cover one eye and then try to
catch a ball tossed at you it's gonna be
a lot harder to catch that ball our
brain uses the images from each of our
eyes and you know each one has a
slightly different perspective and so
from that your brain can build a
three-dimensional map of our
surroundings this is called stereopsis
and lots of mammals and other animals
can do this as well but there really
hasn't been much research on this in
marine animals
now you might expect that cuttlefish
have something similar going on based
solely on watching them hunt but you
know how would you prove that if you
wanted to there's a new paper just out
in science advances titled cuttlefish
used stereopsis to strike and prey and
it's from researchers from both the
universities of Cambridge and the
University of Minnesota now these people
wanted to explore this question and they
wanted to do so using the procedures set
out by another team of researchers who
wanted to answer that question about
praying mantis vision and so this
research was in part inspired by that
research now the praying mantis
researchers looked at 3d movies like you
know Friday the 13th part three and they
wondered could you do the same with a
praying mantis could you show one image
to one eye and another to the other eye
now they achieve this by building
adorable little 3d glasses for the
praying mantis to wear and then they
showed them images on a computer screen
where the Mantis would see one with one
eye and a slightly different with the
other two
see where they would think the prey was
in 3d space so given that 3d glasses
worked so well for mantis research why
not try the same thing for cuttlefish
there is evidence that cuttlefish are
capable of 3d vision they can
distinguish between a real object and a
photograph of it they can use shadows
and lighting to help identify where
something is and they quickly sort of
move their eyes around in a jerky
fashion to estimate distance so-called
psychotic movement so to test this
theory this team of researchers used a
computer screen in coordination with
colored 3d glasses to measure the
ability of a cuttlefish
to correctly estimate the distance
between itself and the prey under
different conditions since cuttlefish
are color blind colored plastic films
were chosen to exclude different
wavelengths of light without impacting
their overall vision each eye was given
a different color filter and then the
computer monitor could show an image in
a certain color that you would only be
able to see for one eye based on the the
color wavelengths that are being
filtered out by the color in the glasses
so in this way they could control
exactly what image each eye of their
cuttlefish was able to see and so from
this they could position the two images
on the screen at varying distances from
each other in order to test how the
cuttlefish would in fact judged the prey
items position and this is exactly how
an old-school 3d movie works by the way
under depending on the distance between
the two images your brain and also
apparently a cuttlefish is brain is
going to position the object closer to
or further away from the screens actual
position cuttlefish actually have four
distinct phases in their great capture
process and those are detection
positioning the starting of the strike
and the actual capture of the prey item
now this team wanted to evaluate the
performance and the impact on their
vision in each phase and so they used a
high-speed camera to record their
experiments along with a GoPro that was
actually in the water with fish this let
them accurately measure exactly where in
the tank the cuttlefish was aiming and
also let them examine what exactly the
cuttlefish was looking at which of
course is an important
trick when your whole point is to see
how cuttlefish vision works now by
following the line of sight from each
eye you're able to see where they
converge and that's where the brain is
going to think the object is so the
larger the disparity between the two
images obviously the further the
cuttlefish are going to converge the
eyes are gonna converge and the further
the prey item is going to seem from the
cuttlefish and in fact the cuttlefish
positioned themselves further from the
screen before striking in those
conditions they were able to prove that
cuttlefish used the variation between
each of their eyes to judge the 3d
position of a prey item and before this
study we only knew that cuttlefish used
the overlapping images from their
binocular vision in their eyes to judge
the position but we didn't know that
they were capable of actual stereopsis
now have you ever played around with one
of those like magic eye puzzles you know
they're the ones where you have to kind
of cross your eyes and get all blurry
and then suddenly something materializes
out of the random dots well they
actually tried a version of this with
the cuttlefish as well and they found
that they're able to pick out an object
from the random dots almost as well as
you and I can and if you want more if
you search online for red blue
random-dot stereograms you're gonna find
a lot of information on these kind of
tests and people actually use them to
test human vision as well they found
that the cuttlefish could pick out the
shrimp's image against correlated and
anti-correlated images but in a totally
uncorrelated image they were actually
interested in the item but they never
struck at the image of the shrimp now
you might be wondering how exactly do
you get a cuttlefish to wear 3d glasses
they don't have ears so how would you
keep them in place
I was wondering this too and it turns
out the team did a really simple thing
they took a little piece of velcro and
they super glued it to the back of each
cuttlefish and you know I'm sure that
this super glue was only temporary
anybody who's touched a fish knows that
they have slime coat and all that kind
of stuff but it works well enough that
they could use it to velcro the glasses
onto the animals for the experiments and
the cuttlefish got used to it and didn't
seem to mind I want to give a really big
thank you to the research team who sent
me all the images that I've been showing
you all through
this video I really strongly encourage
you to check out the paper there's a
link down below like usual but it is
totally packed with information even
beyond cuttlefish vision there's just a
lot of general information about
cuttlefish in this and so I would
strongly recommend giving it a read it's
an awesome paper I hope you enjoyed the
video take a moment to subscribe if
you're new here and have a fantastic day
I'll see you next time bye
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