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Dive Dry with Dr. Bill

#672: A Diet of Worms

I was absolutely shocked... shocked, I tell you... when I discovered that I had never written a single column about a very common critter right here in our dive park. It is even found in shallow coastal waters with soft bottoms in both tropical and temperate regions... at least in the ocean, but that's 70% of the Water Planet. I'm talking about the parchment worm, Chaetopterus variopedatus. It is one of the first species I learned way back in 1969 when I first arrived on Catalina to teach marine biology. But we all know worms are among the Rodney Dangerfields of the world... they just don't get no respect!

These are not creepy, crawly worms that might frighten a squeamish diver (or landlubber). The parchment worm itself is actually rarely seen. It creates u-shaped tubes that are tough and flexible. The two ends of the tube are often seen sticking out of soft bottom habitats. They are elevated well above the surface to avoid sucking in too much grit. They leave that to John Wayne who used to moor his boat, the Wild Goose, above vast fields of them at White's Landing. In deeper waters in some areas the tubes are exposed and attached to rocks and I've found a few like that here, too.

The pale colored worm itself is segmented like its terrestrial distant cousin the earthworm. They may reach lengths of about 10 inches. The parchment worm's anterior (forward) region is short. It consists of several segments that have bristles extending from them, and a mouth that Wikipedia refers to as "shovel-like." The middle section of the worm consists of several segments that bear parapodia, or fleshy-like structures. On the 12th segment these are longer and almost wing-like. This segment secretes mucus that forms a bag-like structure. The next three segments have paddle-like parapodia that create a feeding current which passes through the worm's tube from the head end to the rear. The rear section of the worm's body tapers and has segments that bear extensions.

The parchment worm feeds by trapping food particles from the current inside the tube with its mucus net. Once enough munchies are captured, the mucus net is rolled up and passed forward to the mouth where it is swallowed whole... certainly not my idea of a gourmet meal!

No "Dive Dry" column would be complete without a little sea sex. These worms are either male or female. The ladies may produce 150 thousand to one million eggs which are released into the surrounding waters. With any luck, many are fertilized by sperm released by the males. The larvae drift in the plankton and feed there for several weeks until they settle to the bottom.

Back in my days at the old Toyon school I did a fair bit of research into the dispersal of marine life to our island. My students and I would sample drifting kelp rafts (or paddies for the anglers). We would bring them back to my lab and identify all the critters hitch-hiking aboard them. Several of the kelp holdfasts had the parchment tubes attached to them, and a few contained living worms. I tried keeping some in our lab aquaria by placing them in glass u-tubes so we could watch them create their feeding currents. Unfortunately my tanks had no constant seawater feed so there wasn't much for them to eat. You can also find them on kelp holdfasts that land on beaches, and occasionally storms will create large masses of the tubes on exposed beaches.

These worms can form dense communities on sandy bottoms. In late spring and early summer divers often encounter dozens to hundreds of their tubes scattered all over the sand surface. The culprit is our bat ray (Myliobatis californica). Bat rays come to rest on the sand and start hammering it with their head region, digging large pits to search for munchables. The juicy parchment worms are a delicacy to the bat rays which can significantly impact their numbers. Parchment worms may generate bioluminescent flashes of light when disturbed, so the bat rays may get a light show while feeding. In some areas of the world such as New Zealand, large colonies have built up and excluded many other sandy bottom dwellers, creating a nuisance.

Having learned much of my marine biology during the Dark Ages of decades past (BI, or Before Internet), I am not always aware of new findings until I research these columns. Apparently the relatively new science of molecular taxonomy indicates that what was once thought to be a single species of Chaetopterus may in fact be several. I came from a relatively small family but I think it is always nice to learn one has new relatives.

© 2016 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Horn shark resting on bottom and close-up of dorsal spine; unique egg and very young juvenile.

This document maintained by Dr. Bill Bushing.
Material and images © 2015 Star Thrower Educational Multimedia