Which came first? The spigot or the spinnaret?


Tarantulas produce silk from their feet:

"Researchers have found for the first time that tarantulas can produce silk from their feet as well as their spinnerets, a discovery with profound implications for why spiders began to spin silk in the first place."

I love these sorts of discoveries. Now we have an interesting project - what evolved first and why? Silk for climbing or silk for spinning and prey capture? Some previous work suggested that orb web spinning evolved twice, with one group spinning dry silk webs that use electrostatic forces to capture prey, while another group evolved glue-covered silk to do this. There are as many as seven kinds of silk. If this new silk is homologous with one of the spinnaret based silks, then one will have evolved from the other, since the likelihood that such genes would evolve more than once is vanishingly small. But which was first? The spigot on the legs or the spinnaret on the abdomen? Watch this space (well, watch the journals, anyway).

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