Ready to settle down

  

Okay, back to these little snails that I posted on 27 January 2024!

This would have been a challenging one to identify unless you've spent some time looking at vermetid gastropods, or tube snails.  These are newly hatched Petaloconchus montereyensis!

And if you haven't heard of tube snails — yes, that's right, these are snails that don't crawl (at least as adults) and instead live in a calcareous tube that's cemented in place.  

This species of tube snail is a brooder — the adults lay egg capsules inside their tubes and the juveniles hatch and crawl away.  They only crawl for a brief time before attaching to the substrate — e.g., a rock surface or the tube of an adult.  (They tend to be gregarious.)

One of these snails settled after only two days.  In the video below you can see the tiny juvenile (only ~2 mm across) with the new tube that it produced.  And if you look very carefully you can see the coiled shell that it started out with at the very base of the tube!  So cool!  

As adults these snails are attached to the substrate, so they feed in a different way than many common marine snails.  Instead of grazing on algae on the rocks or in tidepools, Petaloconchus feeds by casting a mucous net into the water, letting organic material get caught in the net, then pulling the net back into its mouth.  The snail uses its radula (like a tongue with rows of sharp teeth) to retrieve the net.  Eric captured some video of that feeding motion, too, so he included it in this clip.  This is pretty spectacular footage of tube snails, so be sure to check it out!

The video sequence goes something like this:

• First 20 seconds — juveniles crawling on their own
• At ~22 seconds — juveniles exploring the outside of adult tube snails
  
• At ~48 seconds — close-ups of the newly settled juvenile with a coiled tube!
• At ~1:05 minutes — miscellaneous shots of adult tube snails with nice views of their radulas in action
  

Thanks for the terrific video, Eric!