tjewell (hydrolagus) wrote,
tjewell
hydrolagus

tiny aquarium excitement today

Most of the exhibits of local species at the aquarium use water from Puget Sound, filtering out only big stuff. The water is returned to the Sound afterwards. This means we get things living in the exhibits that came in on the plankton and decided that our exhibit tasted/smelled like a good place to settle out and grow. This is a positive thing--those exhibits develop a complexity and texture that is nearly impossible to achieve deliberately. The tidepool near the oystercatchers was showing off some of these today: a bunch of (a href="http://bcbiodiversity.lifedesks.org/pages/19695">skeleton shrimp</a> and a small aggregation of some kind of sea slug (sea hare, I think), both very cool and things we never added.
Another thing that we have never added to the exhibit is crabs, but there are crabs aplenty in there. My supervisor and I were looking at the various inverts when she spotted something odd and I identified it as a hermit crab without a shell. It was pretty large, which is probably why it didn't have a shell--the only snails in the exhibit that get bigger than a dime are limpets, which aren't much use for crab homes. It was looking understandably agitated. She managed to round up some shells that had just been removed from another exhibit, one of which turned out to be still occupied by another hermit--more on it in a moment. She put the other four near the original crab which grabbed the closest. It seemed to be having trouble getting in, so she nudged the others closer. Normally, having a Big Thing poking around in the water near it would be cause for a crab to leave, but this one had a single agenda. It settled into one shell and proceeded to examine the other, now that its soft abdomen was protected.
She placed the other hermit crab a bit of a way away so there wouldn't be any conflict over ownership. However, a smaller hermit crab that was using a bit of broken tubeworm casing as a shell immediately dashed out from under a rock pile and was ready to fight for the new ones' shell. My supervisor moved the smallest of the new empty shells over to the scene and the pugnacious little thing promptly relocated into it.
No-one had been aware that there was such an issue and we'll be seeding the exhibit with a variety of shell sizes from here on. Less drama but more hermit crabs is fine.
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