What are these strange round blobs on a Southern California beach?

The internet is abuzz today at the sight of these fleshy-colored grape-sized sea blobs found on Huntington Beach, CA.

Instagram photo by RUSTO

Instagram photo by RUSTO


As something of sea-blob fancier myself, my first reaction was: “oh yeah they’re probably…wait…wait what are these?” According to the first news report I read, these fleshy grapes were ID-ed by Dr. Christopher G. Lowe as sea cucumbers. Now, Dr. Lowe knows his cukes, but I needed more. What kind of cuke?! Where did they come from? Why now?! So I reached out to Echinoblogger Dr. Chris Mah for added intel.

According to Dr. Mah, these critters are known as Molpadia (Caudina) arenicola, or more adorably as the ‘sea sweet potato’. Sea sweet potatoes, like many sea cucumbers (this conversation is getting vegetable-y) live on the seafloor, and their tracks are visible in some of the photos taken by local beach goers.

Screen cap of video found in this news report

Screen cap of video found in this news report


As for where they came from and why, these little tater tots are true So Cal natives. Dr. Mah guesses they washed up in a patch of rough water, but they’re always out there, just not quite so high and dry.

So watch where you step California friends. It’s beach potato time!


RR Helm (61 Posts)

RR Helm is a postdoc studying sea anemones and jellyfish at Woods Hole Oceanographic Institution.

6 Replies to “What are these strange round blobs on a Southern California beach?”

  1. Thanks! Just to clarify. NMNH curator emertius Dave Pawson identified them. And the current correct name is Molpadia arenicola. Caudina was a past name which is obsolete.

  2. Still remember when I saw a sea tulip off the coast of Tasmania and had NO clue what it was! Very fun! PS. Rebecca you need to update your profile! Mindy

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