Crete Nature Blog: The Final Ascent

Just before we begin our push for the summit there are a couple of other little things in this cave that I’d like to draw to your attention. This apparently dead spider up here for instance. As a spider grows it gets too big for its skin but unlike us its skin is its skeleton and although it is flexible enough to allow the spider to move it doesn’t grow like our bones do. Periodically then a spider needs a new skeleton. How it does this is to start absorbing the inner layers of its existing skeleton and use that to start growing a new skeleton inside. It also produces a fluid to keep the old and new skeletons apart. There is an obvious flaw in this arrangement in that the new skeleton must necessarily be smaller than the old one (like Russian dolls) which obviously defeats the object. Undeterred by this drawback, the spider reabsorbs the separating fluid so that the new skeleton is loose within the old one, pumps itself up until the old skeleton cracks and then bursts out. This new skeleton however is extremely soft and flexible and also folded to some extent. The spider then undergoes a growth spurt to inflate the new skeleton to its maximum before it hardens. Result; one new, bigger spider and one discarded skeleton like this one here.

Read on at http://bit.ly/2fCHMkh

Posted on November 10, 2016 08:50 AM by