Wednesday, October 06, 2010

Full circle

It started, I remember, with a broken worm. I had been trying to dig up a tube worm from the beach, with no success. In the process, I brought home the tail end of a polychaete worm. And decided to keep it in a dishpan, to see if it would regenerate the lost head. (It tried, but didn't make it.)

That was over a year ago. Since then, I've moved my critters into a proper aquarium, and stocked it with snails, crabs, hermits, shrimp, and more. I've blogged about it, many times. (Search in the box on the sidebar under "aquarium", or "hermit".) But I've never discussed why I keep at it; it's a lot of work, and sometimes decidedly inconvenient.

I'm incurably curious. At first, I just wanted to find the answers to specific questions; "Will the worm grow a new head?" "How fast do mussels move?" "What on earth is that?"

I started watching the interactions of the animals; who ate what, pecking orders, favourite activities, abilities, likes and dislikes. I was learning something new every day, something I hadn't seen in the reference books. I got more books, and a better camera. I asked more questions. I tried to identify new species that arrived in the seaweed that feeds the crabs. Now, I'm trying to follow growth patterns and look for breeding activities.

I have realized that living with these animals, getting down to their level, watching them every day, I can learn more about them and about their environment than I could with any stack of books.

The littlest hermit, on a bed of barnacles. A hairy hermit, in a shell from Crescent Beach.

I said, 'way back at the beginning, that I was trying to make my dishpan feel like "home" to my poor, headless worm, so I stocked it and arranged it with the biodiversity found on his beach. I have continued with that aim, trying to make a "tidepool" effect. I bring home water, plants and a variety of animals from the intertidal zone of Boundary Bay.( I find the same critters on both sides, in different proportions, true, but still the same mix of species. And the water has the same range of salinity, varied according to the state of the tide and the amount of recent rain.) I've tried to imitate, as well as I can, the conditions found in the intertidal zone.

Can't be done. For one, I can't really keep to a regular schedule of high tide, low tide, high tide, etc, switching every 6 hours. My crabs have no dry ground to crawl up to; they use the top of the pump instead. I keep the temperature more or less constant; on the beach, it varies considerably with tides and currents.

And even my efforts to observe my guests changes things. The crabs respond to me, staring through the glass, sometimes waving claws in my direction. The hermits take food from my fingers. The anemones block my vision, settling down in the "wrong" places, and I convince them to move by prodding at their sides with a plastic spoon.

And worse; when whelks ate my mussels, I removed the whelks. When I had a population explosion among the big polychaetes, I deported them to the beach where they came from. When a flatworm ate a hermit, I banished both flatworms to a jar, then a bowl of sand and water. In "real life", they would change the makeup of the intertidal community; not here.

Be that as it may, the critters adapt to the conditions they find, and go about their business as usual; there is much to be learned, yet.

And back to broken worms; a couple of hours ago, I noticed a large one on the surface of the sand. Hunting for food, I thought, but it was moving oddly, waving about aimlessly, sluggishly. I looked more closely. A big hermit was at the other end, eating the worm; I could see the bloodied end, the head end without a head.

I always thought these big worms had no enemies in the tank. They're bigger around than the largest of the hermits, and too quick to retract under the sand at the least touch of a pincer or clawed foot. Only the large male crab seems strong and fast enough to do them any damage, and he didn't look interested. But something bit the worm in half.

I removed it; I didn't want it dying and fouling the tank; it's more food than the population could eat in a couple of days. I put it in the bowl with the flatworms, where I can remove it easily if it dies. It still swims, though it's missing the head. Oddly, it swims in the direction it would if it had a head, but it doesn't burrow into the sand.

We'll see: will it grow a head? Will it die? Will the flatworms eat it? Same questions I started out with, last year.


  1. Delightful essay Susannah

  2. What an incredible experiment. I'm looking forward to reading about what you observe. Poor headless worm.

  3. Very cool - your aquarium sounds like a fascinating place. We have a similar set up in one of the touch tanks at work; people throw in crabs, shrimp, little fish and squids, whatever they catch in our seine nets, and if some of them eat each other, so be it. I don't really spend much time observing that tank (I'm preoccupied with turtle care) but maybe I'll start!


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