M Is For the Many Things She Gave Me...

June 24, 2010

Tags: Walker, Kim, Amaurobius, Amaurobiidae, spiderlings

Matt Walker over at the BBC's Earth News has a couple of fascinating videos and a somewhat blood-curdling report (at least for those of us who already wonder whether we do too much for our kids) on new research by Kil Won Kim. Kim studied the interaction between mothers and spiderlings and then between spiderling siblings in the subsocial spider species Amaurobius ferox (in the family Amaurobiidae). Yet another reminder that there's more than one way to find food and to avoid predators.

Definitely check out the links to Walker's other recent reports on araneology.

Man Bites Spider

June 22, 2010

Tags: Cambodia, Bristowe, Thailand, Mygalomorphae

A friend directed us to this article about tourists hunting and eating big spiders in Cambodia. Although the article states that Cambodians first began eating large spiders when forced into the countryside by the Khmer Rouge, the practice undoubtedly started long before--maybe even thousands of years before. The great British araneologist W. S. Bristowe reports spider consumption in Thailand in the 1930s, and it's hard to believe Asians and others haven't always dug for spiders. Really, when you think about it, eating a spider is no more disgusting than eating a soft-shell crab. They're both arthropods, with all that taxonomic designation entails. Exoskeleton, jointed legs, segments. Throw in some chili or garlic and you've got a tasty, protein-packed entree.

So it's not surprising that subsistence farmers or other people who struggle to get enough to eat would look to oyster-sized spiders for sustenance. But foreign tourists don't need to eat spiders. Every one of us who extols environmentalism eats something that leaves us open to charges of hypocrisy. The problem with this new tourist trade in spiders, though, is that it probably represents a sudden increase in the number of spiders taken from their burrows, and no one knows how this will affect local ecosystems.

Arthropods aren't as cute as sea turtles or baby seals. But they play vital, and usually underappreciated, roles in ecosystems. These fried spiders belong to the infraorder Mygalomorphae, which includes tarantulas, trap-door spiders, and their closest relatives. Many other kinds of spider complete their full lifecycles in a single year. But some mygalomorphs rack up the years, living more than two decades in captivity. Females in some mygalomorph families aren't sexually mature until they are more than 5 years old. So it's easy to see how too many burrow raids could inadvertently lead to collapse of local spider populations. Burrowing spiders are predators of walking insects and other arthropods, so hunting may also have an indirect negative impact on local farmers' crops.

The local people selling these mygalomorphs to tourists must need income. Maybe tourists could be convinced to pay them to guide catch-and-release expeditions instead.

Silk: From Liquid to Solid

June 14, 2010

Tags: silk, protein structure

A group of scientists in Norway and Sweden reported in the journal Nature last month that they've figured out something new about how spider silk self-assembles. Spider silk, which is a protein, starts out as liquid dope in spiders' silk glands. A protein molecule is a chain of amino acid molecules. As the amino acids up and down the chain interlock with each other in characteristic patterns, the liquid dope transforms into fibers.

The timing of this self-assembly is crucial. If it happened too soon, a spider would be left with balls of silk fiber clogging up its silk glands--useless. Why do the same molecules form a liquid in the glands but form fibers as they emerge from the spinnerets?

Like all proteins, silk protein molecules have two ends and a middle. One end is known as the C-terminus. The middle of silk protein molecules is made up of repeating sequences of amino acids that interlock to form the fiber. And the other end is known as the N-terminus. Silk scientists have known for a while that the C-terminus plays an important role in ensuring correct fiber self-assembly. The new report indicates that the N-terminus determines the timing of self-assembly.

As silk molecules move through the ducts leading from silk glands to spinnerets, they encounter gradually decreasing pH levels--that is, their surroundings become more acidic. The molecular structure of the N-terminus makes it sensitive to such a change, and it in turns influences how the middle, repeating segment of the silk molecule twists back and forth on itself. The researchers found that the N-terminus actually inhibits fiber formation in basic or neutral environments and hastens it at the levels of acidity found out in the spinnerets. So spider silk fibers self-assemble right on time.

One more example of how spider silk proteins may help us understand all sorts of other proteins.

Louise Bourgeois

June 1, 2010

Tags: Bourgeois

The powerful and provocative artist Louise Bourgeois died in New York this week at 98. Her towering Maman made her a favorite of many araneophiles. If you ever get a chance to watch The Spider, The Mistress and the Tangerine, a wonderful documentary about Bourgeois, don't miss it.




Tags

"...a compelling introduction to evolution in action through the lens of spiders and their silks."

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