Monday 7 May 2012

Losing old legs and growing new ones

I see lots of Philodromus spiders with missing legs, some of them with up four legs missing. They are - incredibly - able to walk, and presumably find enough food to stay alive. Many spider species have weak points in their legs, when in danger of being predated or otherwise attacked, they shed them, a phenomenom called autotomy. Spider autotomy has actually been shown to be a voluntary act, as anesthetised spiders would not shed their legs. For a spider, it is costly to lose a leg, as it might impair reproductive or fighting ability, or success at hunting, but it is a small price to pay when the alternative is to be eaten. And the best thing is that sometimes legs are not lost forever, as immature spiders maintain the ability to regenerate lost limbs in the next moult  (although long lived spiders that moult when adult, like tarantulas, do keep that ability for life). The spider on the top shot, enjoying a juicy aphid a few days ago, has regenerated the middle pair of legs on the foreground: notice that they are thinner and shorter than the rest, and lack the colour pattern seen on the equivalent legs on the other side. Even in the Philodromus below, which has lost four legs and a palp, the apparent stumps of the missing legs are actually the miniature folded regenerated legs.


Antje said...

Yikes. I always get a bit queasy when I see things like this, even though I know it's no big deal for the spider. Very interesting post!

Africa Gomez said...

Thank you Antje, Nature really makes you look closer!

BeadleHands said...

I took this photo the other day of a spider that appeared to have a new leg growing.

Werner David said...

Dear Gomez,

I've been fond of spiders since my childhood and right now I'm writing an article concerning the autotomy of spiders. I'll offer this article as a PDF-File on my website With your permission I would like to use your impressive Picture of this biological phenomenon.

With kind regards

Africa Gomez said...

Hi Werner, thank you for your comment. Most honoured you like my photo and you can of course use it if you acknowledge me.

Werner David said...

That's great! :-) Thanks a lot

Kind regards


Here some spiders in my minigarden on my balkony: