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Friday, February 13, 2015

Dining out on the Innkeeper

I received a few inquiries about mystery animals washing up on Doran Beach during the last few days.  Liz thought they could be innkeeper worms, and Phil sent a photo that made it look like a possibility.  Both of them mentioned that gulls were eating the worm-like animals.  

It seemed worthwhile to confirm the identity of these animals, so I took a quick look today.  Sure enough, quite a few innkeeper worms (Urechis caupo), also known as spoon worms (echiurans), were washing up on the outside of Doran Beach (the bay side, not the harbor side), fairly close to the North Jetty.

Here are a few documentary photos of the gulls (primarily Western Gulls) taking advantage of a food resource not often available to them: 

And here's a close-up of an innkeeper worm washed up on the sand, before a gull encountered it:

This innkeeper worm was not in its best formthat is, they normally live in U-shaped burrows in the mud, and I'm guessing it had been out of its burrow for while and that its condition had deteriorated while washing around in the surf.  But you can still see a few important characteristics — the pink coloration, the sausage-like shape, and the golden setae (bristles) at both ends.  The ring of bristles at the posterior (back) end are quite prominent in good light, while the two bristles at the anterior (front) end are harder to see.

Perhaps you're wondering about why they're called innkeeper worms?  I mentioned they live in U-shaped burrows.  A few other animals are resident alongside the innkeeper worms in their burrowssee diagram below:

From Fisher, W.K. and G.E. MacGinitie.  1928.  The natural history of an echiuroid worm (Urechis)Ann. Mag. Nat. Hist. 10: 204-213.  (a) innkeeper worm, (b) scale worm, (c) pea crab, (d) goby.

So the remaining question with this current observation is: Why are the innkeeper worms washing up on the outside of Doran Beach?

Have you seen this phenomenon before?  Do you have ideas about what could be happening?

As far as I know, most of the innkeeper worms live on the mudflats in Bodega Harbor.  Do some of them live on the outer coast?  Or, were they somehow flushed from their burrows in the harbor and then washed around to the bay side and concentrated near the jetty?  If so, how did this happen?  Could it have been related to the storms last weekend?  Did the heavy rain cause channel scouring that removed some innkeeper worms from their burrows?  It is possible they were impacted by fresh water?

Lots to wonder about.  Let me know if you can think of other scenarios that would concentrate innkeeper worms in this way.


Anonymous said...

Hey Jackie,

Drop me a line if you get to the bottom of this one. Feels like an environmental issue. Having grown up on the coast I have long been fascinated with Rechis and never seen this phenomenon. I am very curious about what is happening here.


Anonymous said...

Um, Jackie, for whatever it may be worth.

I think I didn't communicate too well with my first e-mail. I saw these critters on Doran Beach on the 9th, 10th and 11th. I was camped near the Jetty, but never saw them washed up there--I'd likely have noticed 'coz I was mostly looking at gulls and on those three days where there were accumulations of gulls there were worms. Likely the other way around, but I never saw big flocks of gulls without at least a few worms. On the 9th and 10th I saw them on the bay side beach between the picnic shelters and the Lifeguard station, near where folks were surfing. On the 11th there were a couple at that point in the morning, and then none further along the beach. In the morning I walked to the end of the beach, beyond the stairs that lead to the golf pro club and saw no more worms. At about 2 pm I was walking back and maybe 100 yards west (north?) of the stairs there was an accumulation of stuff washed up including lots and lots of the tubular things I mentioned in my e-mail, some one or two inch scraps of reddish segmented coral-like stuff (maybe bryozoan?), and other bits and pieces. It was, I think, the place the waves were breaking highest on all three of the days, and there was some evidence of a rip-tide. There was a big raft of what I think were scoters (definitely not brant) maybe 150 yards offshore. Binocs weren't equal to a definite identification. And that's where the worms were--maybe a dozen of them. They hadn't been there earlier, I'm quite sure. All three times I saw them were near high tide.

There were two women with me, one of whom had the sense to take photos--I don't know who they were but they were local folks. I'm really annoyed that I was too dumb to take photos. I guess the lesson for me is that as an amateur I don't always recognise when something is of interest until after the fact. Sorry.

One of the women mentioned that she was familiar with this blog, so she may see this and send you a photo of the tubular thingies. You've got good worm photos, I see.

Still wondering about water quality, salinity, temperature etc. Anyhow, I can say with certainty that they showed up elsewhere in addition to the ones you saw by the Jetty.

Jackie Sones said...

When I first heard about the innkeeper worms washing up, I thought about recent events that could have been involved and wondered about storms/rain during the previous weekend. I also did a quick Internet search to see if other people had recorded other observations of large numbers of innkeeper worms washing ashore. I found one reference to a similar event in the Monterey Bay area (a few years ago) -- also suggesting it might have been storm-related:


But it's worth considering other options. I'll be asking around to see if anyone has seen this happening before or has other thoughts about what could cause so many Urechis to be removed from their burrows.