A Sand Dollar's Breakfast is Totally Metal | Deep Look

A Sand Dollar's Breakfast is Totally Metal | Deep Look



It’s a beachcomber’s prize. But this sand dollar is just an empty husk…
a skeleton. This is what sand dollars really look like. Off the coast of California, Pacific sand
dollars snuggle up together, like a big pile of purple sea cookies. They’re fuzzy… almost cuddly. But look closer… That fuzz is actually made up of tiny spines…
thousands of them. Some long and spiky, other rounder. Mixed in are miniature tube feet with grabby
little suckers on the ends. They use them to meticulously sift the sand
and pass the grains down the line, until they reach the sand dollar’s mouth – at the very
center of its underside, buried under all those spines. Sand dollars eat sand. They’re after the algae and bacteria that coat the grains. And these sand dollars can also stand themselves
up on their sides to use the long spines around their edges to trap tiny plankton floating
by. So what about that part that looks like a flower with five petals? It’s called the petaloid. They have special tube feet there that help
the sand dollar breathe, absorbing oxygen out of the water. You can see that same five-point body plan
on the skeletons of their relatives – like starfish and sea urchins. In fact, sand dollars are just a type of flat
sea urchin. But while their cousins prefer the rocky shore,
chock full of life and spots to hide…. Sand dollars don’t have such a cozy place
to live. They’re at the mercy of what’s basically
an undersea desert, Thrashed and sandblasted. So being flat is an advantage. They’re sleeker, streamlined against the
powerful currents. And they have another scrupulous solution
for staying put. Not all sand is the same. Mixed in there are some extra-heavy grains. They’re made of magnetite, a type of iron
ore. Scientists think that as they grow, young
sand dollars sort them out and swallow them… grain after grain. The heavy ore builds up inside their bodies
and helps weigh them down to the seafloor. At the California Academy of Sciences in San
Francisco, researchers used x-rays of sand dollars to look for it. See those bright white areas? Those are the pockets of magnetite. That’s how these tireless little creatures
can hack it – out here in such turbulent waters – where most other things can’t. Turns out, it takes a lot of work to just
lay around. Want to know how we got so up close and personal
with those sand dollars? Follow us over to Patreon for a very seaworthy
behind-the-scenes video. Join our community on Patreon to unlock rewards
like members only live streams, bonus content and helping us pick upcoming episodes. Link in the description. See you there.

39 thoughts on “A Sand Dollar's Breakfast is Totally Metal | Deep Look”

  1. When I was young my mom told me about sand dollars when I found it at the beach

    Me (young): mom what's this?
    Mom: oh you found a sand dollar
    Me (young): can you use it?
    Mom: you can take decors out of it

  2. I found a live sanddollar once at the beach in California it was brown and sick from being so close to the beach we put it in a bucket rented a boat and went out really far and put it back in the ocean. we watched it for a while and it started looking healthier in about an hour

  3. I once was looking through the sand for shells and found a really small sand dollar that was smaller than my finger. I found it around maybe 6-7 years ago and I still have it in a ring case so I don't lose it.

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