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Estuarine Mud Flats

The third environment I wanted to take you to is in our own backyard in estuaries and marine mud flats. The sulfide levels in this environment is fairly low. Much lower than the seep and the hydrothermal vent environment, but remember sulfide is toxic at the nanoMolar level so this is still a physiological challenge to animals in this particular habitat. The habitat that I have worked with for ten years now is the marine mud flat environment up and down the California coast. The animal that I have worked with primarily is this beast right here. This is Urechis caupo, the fat innkeeper worm. It lives in u-shaped burrows in the mudflats. You might recognize this slide. It was provided compliments of the California Academy of Sciences. This is from the Wild California exhibit. You can walk in there and see this animal in its habitat. It is called the fat innkeeper worm because there are a number of animals that live in its inn, in its u-shaped burrow. It's quite an active animal. It pumps water, irrigates the burrow actively when the tide is in, spins a mucus net, captures materials in the mucus net, engulfs the mucus net and makes a very good living. So it is a typical animal in terms of its feeding and metabolism. It does not harbor chemoautotrophic symbiants in its gut. It is not utilizing inorganic chemicals like sulfide as the basis of its metabolism. It eats like you and I do.

We collect them from four different environments. This animal is endemic to California. It is a very common visitor to invertebrate morphology science labs all over the United States. I recommend it to you as an easy to collect, and very instructive biological specimen. (I'll hopefully tell you why as I go along.) There are four major habitats for it Bodega Bay has a very well defined population of very large worms out in the mud flat here.

Pillar Point Harbor is our favorite. It is close to us and the worms are easy to collect here. They are very plentiful.

Elkhorn Slough is wonderful. It has huge populations of Urechis. I was at the Moss Landing Marine Laboratory for a year as a visiting scientist, and we used to just go (that was before the earthquake when the lab got wrecked) and we used to just go across Highway 1 and collect.

Morro Bay is also rich with populations of Urechus . So even though you are not aware of them when you walk around on the mud flat, because they are obviously under the mud in burrows and you don't see them. They are quite plentiful.

They are easy to collect. You don't need submarines. We use this lovely slurp gun device which we copied from the fishermen. Fishermen use these animals as bait. They are quite effective bait, apprently. And you can just, with this suction gun go out at low tide, and if you know how to recognize their burrow openings, you can suck them up pretty easily.

Here is a diagram showing the positioning in the tube and that is why you can't see much of the burrow. Again, they have a well defined mouth in the anterior.area, a complete digestive tract, and an anal opening. They spin the mucus net. pump the water through, capture small detrital material and engulf the net ( I actually have some videotapes showing net spinning behavior of this animal...one of my student's graduate projects).