Worms are not one of the more charismatic groups of critters, topside or beneath the sea. I can't remember seeing an environmentalist carrying a sign "Save the Worms" even though they provide very important ecological functions both on land and in the ocean. Folks just don't get too excited about these "icky" creatures. Maybe I can change your minds with today's column... maybe not. I was pleased to see that I've already written about the Christmas tree, sabellid and windmill worms in previous columns. Today I'll focus on a very sticky subject, the terebellid worm known by scientists everywhere as Thelepus crispus. I didn't realize it, but this species does have a few common names including spaghetti, shell binder, or hairy gilled worm and curly terebellid... no relation to any of the Three Stooges.
Diving over the rocky reefs in our region, one often sees numerous long white "threads" radiating out from a small tube-like hole. If you watch closely, you can see these "threads" moving about. If you watch real close, you can actually see bits of food being passed along the length of the thread towards the opening from which they extend. While observing the terebellid worm may not be as exciting as encountering a giant sea bass, it does have its charm... at least for this marine biologist. Worms just don't get no respect. I guess that makes them kind of like me!
Terebellid worms are found from Alaska to southern California, which means we are at the edge of their mostly northern distribution. I did find one scientific report that states they are also found in India, which would pose a significant biogeographical question in my mind! Another states they are found in Boston Harbor which surprises me. As a Harvard undergrad, we dredged there and the only things we found were bottles, cans and an old rubber boot! Here they are found down to about 50 feet in sand or mud habitats, as well as under rocks. Their tubes are usually buried in the substrate, and composed of a membrane covered with sediment. The worm itself may be as long as a foot (12" not one with toes), which came as a surprise to me since their tubes seem very small. Add to that the white feeding threads or tentacles which may also reach more than a foot in length and you have a surprisingly large critter!
When their tentacles sense a potentially delectable particle settling on them, they transport it using mucous and cilia which beat along the length of the tentacle and move the morsel towards the tube opening... and the worm's mouth. Not quite the modus operandi of a vicious predator so we'd probably classify this muncher as a detritus feeder. I've never tried to extract one of these worms from their tubes (biology is the study of life, not a license to kill... I'm not big on formaldehyde). From pictures, I know they are segmented worms (like an earthworm) with a reddish-pink body. They have three pairs of branched reddish gills. Their blood utilizes hemoglobin similar to ours to hold and transport oxygen. In fact, they apparently have two different types of hemoglobin. I do, too... my own, and that from the victims of my fang bites on nights of the full moon!
Since I'm free once again to talk about mating, I'll write what little I know about their sex life. Although some worms cast their sperm and eggs into the water column like many other invertebrates. This terebellid is a brooder. No, it's not depressed or moody... brooding refers to retaining the fertilized eggs within the mother's tube until they develop into larvae. They, too, must either enjoy sex... or have strong maternal instincts... since they reproduce continuously for about six months. Whew! Sure beats my "record!" Each brood may produce over 50,000 larvae. The planktonic larvae of many invertebrates are voracious feeders, but terebellid larvae fast and do not feed (a distinct difference between them and myself).
Some scientific studies suggest that the larvae may sense environmental cues and reject certain habitats as unsuitable to settle in, and others as appropriate. In my research I discovered that the adult worms may secrete brominated organic chemicals that held ward off both bacteria (and disease) as well as predators. Studies of the worm larvae indicate they settle less frequently in sediments which contain these chemicals, so they may also serve the function of "spacing out" individuals within the local population to better ensure food for all.
In the interests of science and education, I spent some time touching these terebellid tentacles on a recent dive. I wasn't trying to get a sense of their texture, but used my finger to make them think I was a predator curious about them. I wanted to video their response as they quickly withdrew their extremely long tentacles back into the tube. If disturbed, terebellid worms may abandon their existing home and move elsewhere to build a new tube. I guess they don't have to deal with issues like increased property taxes, or a change in schools for the youngsters when they move. Of course I was careful not to disturb them too much and force them to uproot and move on.
NOTE: At the recent Long Beach SCUBA Show, Dr. Bill was interviewed by Greg Holt of SCUBA Radio for the upcoming episode of his radio broadcast Saturday on Sirius Satellite radio channel #122 (also available at www.scubaradio.com) . Tune in, turn on (the radio that is) but don't drop out to see if Dr. Bill made it past the digital cutting room floor!
© 2007 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles," "Gentle Giants: Giant Sea Bass" or "Common Fish and Invertebrates of the Sea of Cortez" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!
Terebellid worm tube (to left of sea urchin), top view of tube opening;
feeding threads extended and partially withdrawn.
This document maintained by
Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia