"Rev Dr" Lenny Flank
Posts: 2560
Joined: Feb. 2005
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| Quote (Guest @ June 28 2006,06:26) | Getting back to the subject, it should perhaps be pointed out that spider silk didn't originally evolve for making webs. The group of arthropods from whcih spiders may (or may not have) evolved, the trigonotarbids, didn't have any spinnerets and presumably didn't have any silk. One of the earliest known spiders, Attercopus, at 380 million years, did. Of course, one of the defining characteristics of spiders is that they have spinnerets.
Some of the most primitive of the existing spiders are the mygalomorphs, the group that includes the tarantulas. Some living species of tarantula-like spiders still have segmented apparent in their abdomens, and they are probably very similar to the most primitive of spiders. This group goes back to 300 million years in the fossil record. And although they have spinnerets and produce silk, they don't make webs. Their silk is used largely to make eggsacs, and to line the burrows that they live in. A few species of trapdoor spiders use silklen lines to make a radiating pattern with their burrow at the center, which alerts them to passing prey. It seems likely that prey-catching webs were a (much) later modification of that strategy.
There are also arboreal species of tarantula, which live in silken shelters that they spin high up in trees. They too, however, don't make webs. It seems a good likelihood that they adapted to an arboreal lifestyle in order to avoid monsoon rains which flooded their terrestrial burrows, and it seems likely that the modern orb-weaving spiders began with a similar lifestyle. |
Can anyone point out anything remotely objectionable in this post, placed in the "spider" thread, that would require it to be banished to the Wall?
Other than the simple fact that I am the one who wrote it, and PZ now has a hard-on for me?
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Editor, Red and Black Publishers
www.RedandBlackPublishers.com
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