Thomas' Plant-Related Blog

On plant science. Mostly.

Spider husk

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I spotted a spider’s shed skin, stuck to its web outside my window yesterday. It was too dark to get photos, but I nabbed it and put it in a jar. Today, I got my hand lens out and took some photos. It’s not plant-related at all, but it’s still pretty cool:

N.B. Pictures are not recommended for arachnophobes!

Spider husk

A massive group of animals, including spiders, but also insects, crabs, millipedes, nematodes, velvet worms and ‘water bears’ all have to shed their skins as they grow. The process is called ‘ecdysis’, and the group of creatures that do it are called Ecdysozoa. A new layer of cuticle forms beneath the old one, the animal then breaks down the inner layers of the old skin and re-absorbs the nutrients, but the outer shell is too tough to break down. So, it splits along the back, and the animal pulls itself out. It then has to expand the old skin (if it couldn’t get bigger, the whole exercise would be a tad pointless). So the new skin has to be soft, at first, which may leave the animal vulnerable to predators (it may hide away to moult). When it’s expanded, the new skin will harden to protect the animal.

At least for the land living animals that do this, they leave an exquisite, but terribly fragile, replica of themselves behind. It’s very light—I had to be careful not to breathe hard on the skin, or it would blow several centimetres over my desk—and I guess that it would disintegrate within a day or so exposed to the elements.


Written by Thomas Kluyver

2 August, 2009 at 1:39 pm

Posted in Photos

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