Tuesday, February 06, 2018

High flyer

The ocean surface temperature along the east coast of Vancouver Island varies from about 6.5 degrees Celsius in February to a maximum of approximately 13.5 in August, our hottest month. (That's 45 Fahrenheit to 55 F.) My aquarium sits in a warmish room, with an average temperature of 20 to 21 degrees Celsius in the winter, more in summer. It's too hot for my intertidal invertebrates here, even in midwinter.

I keep everybody happy and healthy by adding ice to the tank. I freeze tank water in yogurt containers that have never seen detergent (which will poison some of the animals) and exchange them for the ones floating at the top of the tank several times a day. It's not pretty, but it works.

This morning, when I went to change the ice, I found a naked hermit riding the yogurt container. How he got up there, I don't know; he can't swim.

Hairy hermit, freshly molted.

When hermit crabs molt, they have to leave their shell. Often it won't fit any more when the molt is finished; all their growing happens in those few minutes between a molt and the hardening of their new skin.

They're vulnerable in this situation. Crabs aim for that juicy, curly abdomen. Fish, too. Luckily, there are no fish in this tank, but there's one big, starving (to hear her tell it) green shore crab. So the hermits head for the highest spot they can find to wait out the growing time. This one somehow found his way onto the iceberg.

It was a good choice. He'd already been damaged; he's missing his main defensive weapon, the large pincer on his right side. He uses the smaller one on the left to manipulate his food.

To replace the ice, then, I removed the yogurt container carefully, hermit and all. I put him into a bowl with a few empty shells for him to choose between whenever he was ready. 5 minutes later, he was dressed and rarin' to go. He had probably been waiting on the floating container for some time, not knowing how to get off without risking dropping into the waiting crab pincers.

With a good shell (according to him: he chose a broken one, well worn and covered with algae. He knows what feels best.) he went safely back into the tank.

(Look back at the photo. Look at the first foot on the upper left. It's not usually apparent that the legs are basically transparent, but here you can see the design on the yogurt container showing through.)

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