Rich Mooi: Sand Dollars and Their Holes | California Academy of Sciences

Academy researcher Rich Mooi talks about sea urchins and sand dollars and why many sand dollars have holes.
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[@ConectoP]

Very interesting video! I wondered why they have that holes!

[@AngrySinn]

I have a couple different species in my collection, dead ones of course. These little guys are extremely fascinating.

[@bagofsoda7464]

they punch holes in themselves?

[@carolynczysz7584]

I found a bunch of sand dollars with no holes at all... WHY?