Cephalopodcast

Parchment tube from Chaetopterus mixed with thousands of dead urchins, © Jason Robertshaw

What the Shell Is That? is my semi-irregular series on beachcombing and tidal life. Living on the west coast of Florida, it is mostly about shells, but can also be about other flotsam, fauna and even flora.

Parchment Tube Worms (Chaetopterus sp.)

Date: 12 March 2008
Location: Siesta Key, Sarasota, Florida, U.S.A.
All along the wrack line.

Kingdom: Animalia
Phylum: Annelida
Class: Polychaeta
Order: Spionida
Family: Chaetopteridae

Parchment Tube Worm (Chaetopterus sp.)

Report:
We had some storms roll through recently that managed to dislodge quite a number of benthic invertebrates. All kinds of critters were washed up on the beach, some in the thousands. There were worms, sea urchins, sea shells and seaweeds of all different kinds and colors. It was good pickings for the beachcombers but even better pickings for the shore birds.

One of the castoffs that piled up in the wrack line were the casings from parchment tube worm (Chaetopterus veriopedatus). Normally these worms burrow into the sand with either end of the tube poking out (see illustration here). The worm itself has several highly modified, bell-like paddles that they beat inside the tube to maintain water circulation. One of the neatest aquarium exhibits I’ve seen was a live Chaetopterus placed inside some clear vinyl tubing. It was thereby possible to watch the rhythmic beating of its paddles. Here’s a photo of a similar set-up.

Another critter that my wife found was one that has long been on my life-list but is so obscure I did not recognize it at the time (hence the poor picture). It was a Polyonyx sp., or a commensal porcelain crab that lives almost exclusively in the tubes of parchment worms. It is rare to find them anywhere else and this one presumably was dislodged from one of the many casings on the beach. You might note how it’s claw seems oddly bent. It wasn’t broken but appeared to be shaped that way.

There were also casings from another type of worm called the decorator or plumed worm (family Onuphidae). You may have heard about the recent debunking of bug eyespots as being mimicry. Well there is a similar amazing story underwater with these creatures. Recent research from Sarah K. Berke and Sarah A. Woodin (University of South Carolina) suggests that the Onuphid’s tube decoration may not be for camouflage after all.

References

• Ruppert, Edward and Richard Fox. Seashore Animals of the Southeast. Columbia: University of South Carolina Press, 1988. 203.
• Williams, Winston. Florida’s Fabulous Seashells. City: World Publications (Tampa, FL), 1988. pp. 39
• Witherington, E., Blair and Dawn Witherington. Florida’s Living Beaches. City: Pineapple Press (FL), 2007. pp. 125.

Additional Links

• Woods Hole Marine Biological Laboratory: Chaetopterus variopedatus (Tube Worm). Includes nice pics of the worm and Polyonyx.
• Polychaet Diverstiy and Feeding: Chaetopterus
• Science Musings: Red fish, blue fish…
• Google Docs: A Study of the Life History and Habits of Chaetopterus Variopedatus, By Howard Edward Enders (Published 1906)
• Biological Bulletin Online: Tube Decoration May Not Be Cryptic for Diopatra cuprea (Polychaeta: Onuphidae) Berke and Woodin Biol Bull.2008; 214: 50-56
• National Geographic: Hawai’i’s Unearthly Worms
• ScienceDaily: Zoologists Challenge Longstanding Theory That ‘Eyespots’ Mimic The Eyes Of Predators’ Enemies