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The case of the six-legged spider

The case of the six-legged spider

A SPIDER climbing a tree in central America, some 20 million years ago, was hit by a blob of resin and drowned.

Well, okay… you might say – a nasty way to die, but it was a long time ago, and lots of spiders have been eaten or washed down plugholes since then. It's time to move on. Except that, due to the miraculous properties of amber, it's possible to reconstruct this tiny tragedy in astonishing detail – as if we were standing by the tree when it happened. Dr David Penny, a post-doctoral researcher at Manchester University's School of Earth, Atmospheric and Environmental Sciences, has studied the piece of amber in which the unfortunate arachnid is preserved. The results are intriguing: the spider (Filistatidae) is only the second known fossil of this family, and – a palaeontological first – Penny also found traces of the creature's blood. The two droplets of blood, technically known as haemolymph, are the first identified examples of spider blood ever found in an amber fossil. It is possible, Penny speculates, that the blood could be used to extract ancient DNA. The fossil, which is 4cm long and dates back to the Miocene period, belongs to the Museo del Ambar Dominicano in Puerto Plata, Dominican Republic. The researcher has used the blood droplets inside it to trace how, when, and where the spider died all those years ago. Penny said: "It's amazing to think that a single piece of amber with a single spider in it can open up window into what was going on 20 million years ago. By analysing the position of the spider's body in relation to the droplets of blood in the amber we are able to determine how it died, which direction it was travelling in and even how fast it was moving." In the latest issue of the journal Palaeontology Penny reconstructs the creature's final moments. He believes the spider was climbing up a tree when it was struck head-on by a sudden strong flow of resin. The spider then became engulfed in the resin and died. Penny argues that the shape and position of the blood droplets reveals which direction the spider was travelling in – the droplets were stretched, forming a ‘tail', as the resin continued its downward path. Penny also reveals which of the spider's legs broke first – the fossilized blood is seen to be still oozing from its snapped-off right patella, whereas the second droplet is distinctly removed from the detached left leg. So, the left leg got it first… I told you: it's like watching it happen. I can hardly bear to look. TM Satterthwaite

‘Fossil Blood Droplets in Miocene Dominican Amber Yield Clues to Speed and Direction of Resin Secretion', Palaeontology (2005, vol. 48, part 5).

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From HERO