platycryptus:

golvio:

platycryptus:

zooxanthele:

platycryptus:

sand dollars doin their thing

they’re basically sea roombas

I mean, I knew on some fundamental level that they’re related to sea urchins. I knew that the parts that I find on the beach are their skeletons.

WHY DID THIS VIDEO SURPRISE ME??

They aren’t just related to sea urchins, they are sea urchins.

They’re just a group of really flat sea urchins with really short spines

who eat sand

Actually, sand dollars eat plankton. They just hoover it up from the sandy sea floor.

Some species do catch plankton in that manner to supplement their diet, but the most common form of sand dollar feeding is swallowing sand and scraping the biofilm of algae and bacteria off the individual grains.

https://youtu.be/dxZdBPDNiF4

Sand dollars eat sand in the same sense that earthworms eat dirt.