Dive Dry with Dr. Bill

#181: The Windmill Worm

Ah, the Internet is such a great thing. I'm so glad my Harvard classmate Al Gore saw fit to "invent" it back in 1969. No, it isn't the porn that attracts my attention. Now, I'm no prude... my readers certainly know my mind is full of prurient interest! Just too many... er... unwanted pop-ups on those web sites for my taste. Besides, I just can't get excited by pictures of women I don't even know. I prefer one I know intimately, fleshed out with a personality and behavior. But not having had a real date for several years... what do I know. Enough of this digression... read on.

What really excites me is the discovery of a new species, or a new behavior for a "well-known" species underwater. Of course nudibranchs ("naked gills") are a real turn on. It must be some strange form of mutation in my genes. A few weekends ago I was diving on Scuba Luv's King Neptune and we stopped at Ship Rock for the first dive. That day the light winds favored anchoring on the south side of the pinnacle, a part of that site I'd only explored above 80 ft. Now I know I said I wouldn't be doing a lot of deep diving, but I knew Brett and Shelly of Haven's Reef were taking their class down the anchor line to 130 ft. I decided I'd drop down just ahead of them and see what I could find. If anything happened, I had my pony bottle and they were only a few tens of feet away (so near yet so far).

I ended up descending to 180 ft, the maximum I am willing to go on air. As I started working my way upslope towards Ship Rock itself, I suddenly noticed a lot of tiny windmill-like creatures on the bottom. They ranged from about 1 to 3" high and were projecting from what appeared to be tubes buried in the sand. These tiny tubes had a series of what I assumed were tentacles extended like a windmill's blades from the tube's opening. At first I thought they were part of the animal itself. I don't remember ever seeing these critters before, but in my previous years of diving I usually stayed above 100 ft. I took a few short segments of video since I didn't want to exceed my allowable bottom time. I had not entered deco as I started to kick slowly up to shallower depths, but made a number of very conservative safety stops and spent quite a bit of time at 15-25 ft at the end of the 45-minute dive.

I started editing the footage that Monday night and was pleased to see the windmill critters came out OK. I had forgotten to charge my video light battery the night before, so I had to take the footage under what light was available at that depth. Fortunately, it was enough. I tried counting the "tentacles" to see if they would give me a clue as to the critter's identity, but found the number wasn't uniform on each animal. At first I thought it was a hydroid or a sea anemone, but the tube construction didn't seem consistent with that group. I decided to post the picture on the web site to see if anyone out there could ID it and save me hours of research. Within 24 hours I received a reply from Leslie Harris at the Natural History Museum of Los Angeles County. She said it was "commonly" known as the windmill worm, a member of a group known as the bamboo worms, and gave me a little information about it.

The windmill worm is a polychaete or segmented worm distantly related to the common earthworm on land. It builds a tube about 1-3" tall that it lives in. At first I thought the tube was membranous, but Leslie later said it was formed from small particles of sand cemented together. The opening of the tube has a series of 6-12 spokes or rays extending outward in a plane forming the blades of the "windmill" I referred to earlier. These spokes are also formed of fine grains of sand cemented together. Then the worm weaves a web of mucous strands on the ray structures just like a spider would weave its web on the stems of a plant. The sticky mucous captures particles of food that fall onto it. Then the windmill worm swallows the mucous, food and all, and weaves another web.

I posted the pictures on several diving-related Internet sites and received a few replies from divers who had seen them in San Diego and off the old Marineland site on the Palos Verdes Peninsula. They were quite pleased to have an ID of this unusual invertebrate, and had pictures of their own to share. I found out from them that the windmill worm could be seen at depths of 35-65 feet. Now that would be a much more reasonable (and safer) depth to film them in! In the picture below you can barely make out one of the worms on a spoke of the "windmill" in the top left, and the mucous webbing on the "windmill" in the bottom group (second from left).

So now perhaps you see why the Internet plays such an important role in my life when I'm not underwater! It is a great research tool, although one must have built-in BS detectors and fact checkers to be sure of the content you find. And I really enjoy the dialog I am able to have with divers across the globe by visiting sites like and In fact, it was through one I met the woman diver who may become my first real date in years. Don't bother staying tuned though since I may not reveal any intimate details of that munching and, er... mating date!

As you read this, I should be in Washington DC to give a eulogy at the funeral of one of my closest friends from my Harvard days. Jim passed away last week due to complications from a lymphoma in his brain. Perhaps his high school classmate and our classmate at Harvard, the "inventor" of the Internet, will be there as well. If so, I can thank him for all the wonderful things "his" invention has brought to my life.

© 2006 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, "or "Giant Sea Bass" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

A group of windmill worms (Praxillura maculata) on the bottom at 180 ft off Ship Rock
(note worm at 2:00 on far left windmill and web on windmill second from the left in the lower group).

This document maintained by Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia