Monday, October 27, 2014

A Molting Tarantula

Last week, one of our Chilean rose tarantulas (Grammostola rosea) molted. This event is one of the most dramatic non-emergencies an Animal Caretaker is apt to encounter. In fact, the process is so stressful looking, it's common to confuse a molting tarantula with a sick or dying one. Often it’s hard not to intervene and 'help'.

Prior to molting, a tarantula builds a silk nest and lies down on her back in the middle of it. She appears to be in her death throes, but then with almost impossible effort, she bursts her way out of the old skin, revealing a velvety, fresh new spider underneath.

The picture above shows our spider, Roslyn, (on the left) immediately after she freed herself of her old skin. She is waiting for her legs to fully expand. Every few minutes she stretches all the legs on one side or the other, probably as she pumps fluids into them to fill out her skin.

For several hours after molting, the spider is totally helpless. Her new exoskeleton needs to expand and harden. Since spiders usually support their full weight on their legs, this is a problem; her legs are too weak to support her body. The tarantula must stay on her back until her legs are strong enough to support her body.

The lighter colored form, on the right, is Roslyn's old skin, lying empty beside her.

In related arachnid news, a newly discovered species of tarantula from the Amazon has been named after a Beatle. Imagine!

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