Tarantula (side view). Photo by Senta Niederegger.
Posted on 09/27/2006 7:16:29 PM PDT by PatrickHenry
Discovery could have implications for evolutionary origin of spider silk
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.
Adam Summers, a UC Irvine assistant professor of ecology and evolutionary biology, was among the team of scientists who made the discovery using zebra tarantulas from Costa Rica. The team found that the tarantulas secrete silk from spigots on their legs, allowing them to better cling to surfaces. Until now, spiders were only known to spin silk from spinnerets located on their abdomen and to use the silk to form webs for protection and capturing prey rather than for locomotion.
The findings are published in the current issue of Nature.
“If we find that other spiders in addition to these tarantulas have the ability to secrete silk from their feet, this could represent a major change in our evolutionary hypothesis regarding spider silk,” Summers said. “It could mean that silk production actually originated in the feet to increase traction, with the diversity of spinneret silk evolving later.”
The researchers placed tarantulas on a vertical glass surface. Though ground dwelling, these spiders can normally hang on to vertical surfaces by using thousands of spatulate hairs and small claws. However, the scientists noticed that when the spider started to slip down the surface, it produced silk from all four pairs of legs, allowing it to adhere to the glass for more than 20 minutes. The silk secretions were clearly visible on the glass. Using scanning electron microscopy, the scientists also were able to see the openings on the legs that resemble the silk-producing spigots on spider abdominal spinnerets.
The next step, according to Summers, is to investigate whether the silk produced by the feet is the same as that produced by the spinneret. Many spiders can produce seven different kinds of silk. Scientists will look at the genes involved in silk production from the feet, compare them to the gene family that leads to spinneret silk production, and be able to better determine whether silk was originally used for traction, or whether that was a secondary usage that came later.
Collaborating on the study were Stanislav Gorb of the Max Planck Institute for Metals Research in Germany; Senta Niederegger of the Friedrich Schiller University of Jena in Germany; Cheryl Hayashi of UC Riverside; Walter Votsch of the Max Planck Institute for Developmental Biology in Germany; and Paul Walther of the University of Ulm in Germany.
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Cool!
I had one hanging upside down on my back porch the past spring. He stayed there for a day then moved on.
I think it's important to determine whether this is unique to tarantulas.
My guess is that it is, or at least only with any closely related species with thick legs.
My gut instinct is this is something that benefits only thick-legged spiders, although that doesn't prove who came first.
We're the spider family right now. My son's doing a book report for his fourth grade te4acher, and my daughter's reading Charlotte's Web--a great story with some truth and contrived facts about spiders. Thanks for the info.
The Tarantula has to be one of the coolest spiders. I wish I had a few loose around my house, as they tend to get rid of much less than desirable life forms. Thanks for posting this!
In order to show that "diversity of silk" into webs only happened *after* the spinning of silk from the feet for traction, it would have to be shown that the spinnarets on the feet predate the spinnarets on the, err, posterior orifice region.
Did the article get into that?
Cheers!
When posting *anything* on *either side* of a crevo thread.
There, I've set my web, let others walk into it :-)
Cheers!
Growing up in rural Oklahoma I had the opportunity to catch and hold turantulas often. They are, IMO, the most docile creature I have encountered. They will crawl on you without malice and it seems even enjoy being pet. I know that sounds creepy, but it's true.
Also, another counter to this scientists claim that the leg thread evolved before the spinerette is the fact that the silk is not only used to catch prey but to "cacoon" it as well. A process which, if I'm not mistaken, the abdominal silk. This allows the spider's kiddos to be able to feed without fear of the larger insect injuring them.
Meanwhile, caterpillars (of both butterflies and moths) produce silk from their heads, near their mouths.
---The Tarantula has to be one of the coolest spiders. I wish I had a few loose around my house, as they tend to get rid of much less than desirable life forms. ---
Like unwanted girlfriends?
Yeah, but can they spin nylons?
What the hell?
I am in as much dismay of this conclusion jumping as you are, believe me. IMO, it's a silly conjecture to attempt to create more importance to both the scientist and the science.
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