On the half shell

 

 

So we were walking at Dillon Beach this week and Eric looked down to see this large clam shell wedged in the sand under water.  It wasn't completely white inside, so he was curious about what looked like tiny yellowish dots in the center of the shell.

 

He picked up the shell and I took a look with my hand lens, but I couldn't tell what they were.  I couldn't even tell if they were hard (with a shell) or soft (gelatinous).  But Eric wiped his finger over a few of them and realized they were soft.  Hmmm...were they egg masses of some sort?

 

But because we couldn't see any detail, we decided to scoop up some seawater to fill the clam shell and see if any other hints would be revealed.

 

We were a little surprised, but here's what we saw next:

 

 

Tentacles!  It might be hard to tell from the photo, but we actually couldn't see the tentacles themselves.  They were too small and didn't stand out from the white shell in the background.  It was the shadows cast by the tentacles that were most apparent.  Here's a closer view:

 

 

 

The tentacles made the answer easier.  These are tiny jellyfish polyps.  You might remember that I posted about some different polyps on the docks in Bodega Harbor in late June — see "Soon to be jellies?" on 29 June 2023.

This is the first time we've observed jellyfish polyps on a clam shell.  It's likely we've just missed them, but now we'll know to watch for them.

 

 

The polyps need to attach to a hard surface, so on a long sandy beach, a clam shell might be prime real estate!