Full Worm Moon

Earlier this month I looked at the calendar and noticed that the full moon this morning (on March 27th) was called a Full Worm Moon.  Although the name originates from earthworms becoming active at this time of year, below is one of my most recent worm stories.

I was looking through a microscope at a small piece of a kelp holdfast (from Salmon Creek Beach) and noticed a very long, slender orange-colored worm crawling along.

 

The worm just kept going and going and going...it was like watching a train go by...and I just kept seeing orange and orange and more orange.  And then all of a sudden the tail end of the worm appeared and it was...

 

...purple!  A beautiful pale purple!

Here's a close-up of the tail end outstretched:

 

And one more, even closer.  There was a neat squiggly pattern on the very tip that somehow reminded me of rattlesnake's tail.

 

  

This worm was very fast moving, so I had some trouble taking pictures of it.  Here's the only image I managed to get of the head.

 

Sadly, I'm not sure which species this is.  I'll be asking around for some help with the identification. If you have any thoughts about it, I'd be grateful for any assistance.

ADDENDUM (28 March 2013): Leslie Harris from the Natural History Museum of Los Angeles County wrote that this worm belongs to the Family Syllidae.  In addition, she notes:

"The pink tail is packed full of eggs & developing into an epitoke.  At some point that section will produce a pair of eyes, drop the normal setae & produce specialized setae with oar-shaped blades, then break away from the parent in order to swim up to the surface to spawn.  The "rattles" are the margins of the digestive tract seen through the skin."  

Thanks, Leslie!

We had wondered whether the tail end was developing into an epitoke, but I didn't want to assume anything without knowing more about the species involved.  As you can see from Leslie's description, an epitoke is basically a swimming stage of a polychaete worm that is capable of sexual reproduction — it will release eggs or sperm (depending on whether it's a female or male).  Epitokes often form synchronized swarms that are coordinated with lunar cycles.  Swarming is thought to increase the chances that eggs will be fertilized.