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The Recipe For A Perfectly Sticky Web May 31, 2009

Posted by Mrs Weird Scientist in Animals, Brain Power, Evolution, Insects, Tough Stuff.
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Have you ever tried to bake a cake, only to find out that when it came out of the oven, it was dry and hard? Maybe you realized that you’d put in too much sugar. Or, maybe you cooked it for too long. Would you believe that spiders have a similar challenge when it comes to spinning their webs? Too much of a good thing can actually leave a web that’s far from perfect.

For this web to catch its prey, it needs to have just the right amount of stickiness and strength.  If all goes well for the spider, dinner will soon be served!

For this web to catch its prey, it needs to have just the right amount of stickiness and strength. If all goes well for the spider, dinner will soon be served!

For a spider to catch its prey, the web needs to be sticky but still remain strong. If the balance isn’t right, the web won’t catch a bug and it’ll be one hungry and grumpy spider!

A Killer Web Evolves

If you’re a spider, you’ve got your work cut out for you! To catch your prey, you want a web sticky enough that the bug gets caught inside but strong enough that the web doesn’t break from its struggles. With such a fine balance needed, spiders have evolved to get it just right.

Let the Construction Work Begin

To build those impressive webs we see, spiders start by putting down lines of dry silk. Then, they weave spirals of sticky silk to nab their prey. But, spiders of yesteryear didn’t build their webs in quite the same way.

Millions of years ago, spiders would lay down a coating of dry adhesive on these spirals. Rather than stick to the web, a bug would be entangled by these dry spirals. As a cool fact you can throw out at your friends, there are still some spiders today that weave their webs with this dry adhesive – we call them deinopoid spiders.

Yet things began to change, with orb weaving spiders evolving to make webs that were more effective at catching prey. Rather than continue to use this dry adhesive, spiders started to go the sticky route by using wet drops of a glue-like substance. When you think of glue, it seems that the sticker the glue, the better. Not for spiders though!

Curious Scientists Start Investigating

Some scientists started to wonder about these sticky webs – is stickier always better? To find out, Ingi Agnarsson of the University of Puerto Rico in San Juan and Todd Blackledge of the University of Akron in Ohio went on a mission to check out a lot of different spiders. They observed 17 species of orb weaving spiders. You’d have to like spiders quite a bit to watch so many different kinds! The full study results are in the Journal of Zoology.

It’s All About Force

The researchers tested the strength of the strands and the stickiness of them too. How’d they do that? Well, they stuck a piece of sandpaper in the web and then measured how much force was required to remove it.

To break a strand on the web, a specific amount of force is needed. When the researchers put the web to the test, they found that by using anywhere from 20% to 70% of this force needed to break the web, the sandpaper was released.

So, a stickier web might hold the insect but as it continues to struggle, the force would ultimately break strands of the web, causing the insect to be released. Yet, with the glue being a bit less sticky, the insect could pull away from a single strand, but it would get caught by the next one. Since the strands don’t break, they can continue to stick to the bug, making its fight a much harder one.

Spiders Are Impressive

It’s actually really impressive and cool when you think about the work that goes into creating a web with just the right balance of stickiness and strength. As for me, I’ll leave the bug-catching to those smart spiders. I think I’ll just stick to making cakes instead. Pun fully intended! Now if only there was a recipe for making good jokes…

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Hairy Frogs Have An Unusual Defense June 2, 2008

Posted by Mrs Weird Scientist in Animals, Tough Stuff.
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When I think about frogs, I usually picture the cute, little ones hopping around the lake near my house. Well, there are many types of frogs and one in particular is almost the stuff of nightmares! Not only is it a super duper hairy creature but it has a peculiar defense mechanism that has intrigued scientists.

Hairy Frog

Credit: Gustavocarra for Wikimedia Commons. Check out the claws on this bad boy! If the hairy frog feels threatened, he will bring forth his dangerous claws through the toe pads on his hind legs. Hmmm. I have a feeling that unlike dogs, throwing him a treat won’t make him like me!

Trichobatrachus robustus – as the frog is formally named – breaks its own bones to create special claws that force their way through the frog’s toe pads. It’s thought that this action is performed when the frog is threatened. While we already know that salamanders do something similar by pushing their ribs through the skin to create spiky barbs, the frog’s maneuver is unique! Not only that, but the closest action we’ve seen from other frogs involves bony spines that stick out from the wrist. The difference, however, is that the bones project out naturally, which is different from the hairy frog where the claws force their way out as a form of defense.

Beware The Claw

David Blackburn from Harvard University has studied these interesting frogs; the work is published in the journal Biology Letters. Blackburn found that when at rest, the frog’s claws are sheltered in a bunch of connective tissue. A piece of collagen joins the sharp bit of the claw and a bone found at the tip of the frog’s toe. At the other end of the claw is an attached muscle. Blackburn thinks that when the frog is threatened and under attack, it will contract the muscle, which causes the claw to be pulled downwards. Then, the sharp bit tears away from the bony end and pokes through the toe pad. The end result is a contraption that looks really intimidating. But wait, there’s more to the hairy frog than just these claws! They also have some other neat features. When they breed, male frogs produce long strands of skin and arteries that resemble hair. While researchers aren’t totally sure why the hair exists, they think it might be to bring in more oxygen through the frog’s skin.

Feeling Hungry

In some parts of the world, these hairy frogs are cooked and eaten. Yes, you did just read that correctly – food! The people who hunt the frogs have to be careful not to get hurt by the frog’s claws, so they use spears and similar weapons to capture the creatures. Now, I’m all one for trying new foods but in this case, I think I will pass, thank you very much!

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Blame Your Brain For Temper Tantrums March 9, 2008

Posted by Mrs Weird Scientist in Human Body, Psychology and Behavior, Tough Stuff.
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Temper Tantrum

Temper tantrums aren’t just a reaction that young kids exhibit when they get upset or angry. Teens can also go berserk over all sorts of issues. Yet, some teens seem to keep their cool while others fly off the handle at just the slightest aggravation. Now, a study suggests that the connection may lie in a teenager’s brain.

Checking Out Families

Nicholas Allen from the University of Melbourne, Australia investigated 137 children between the ages of 11 and 14. As part of the experiment, he also observed their parents. Allen and his team of researchers used questions – such as curfews – that were expected to trigger arguments. They videotaped these disagreements and found that there were loads of differences between the families. Some families kept calm while others were more aggressive and could barely even speak to one another.

What An Enormous Amygdala You Have

When researchers took scans of the children’s brains, they narrowed in on three specific areas. The first was the amygdala, which is what gets people fired up to react impulsively to situations. The other parts they checked out were pre-frontal regions known as the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC) – areas of the brain that play a role in the more thoughtful types of responses. The results were really interesting!

Brain

Researchers found that the boys and girls who reacted more aggressively to the family discussions had bigger amygdalas. As for the temperamental boys, they had smaller ACCs on the left side of the brain, which researchers think explains why they remained aggressive for a longer period of time. On top of that, the boys who had smaller OFCs on the left side were more likely to respond to mopey parents by acting just as moody!

Making Sense Of The Results

Basically, what the results show is that those grumpy, tantrum-prone teens aren’t getting enough control from the pre-frontal parts over the amygdala. So, the impulsive behaviors end up ruling over the thoughtful and more reflective areas of the brain. What’s the end result? You got it – temper tantrums! The results also suggest that the areas of the brain controlling emotions and aggression are different in boys and girls.

My title for this blog entry is actually a bit misleading because it implies that the structural differences in the brain are fully responsible for aggression, when this just isn’t the case. The research gives us helpful clues to one contributing factor in the puzzle of temper tantrums. Learning more about why some teens are calm when others can freak out so easily and intensely can perhaps allow researchers to find better strategies for helping teens handle their aggression. As for my teenage years, I didn’t blame my brain for temper tantrums – I usually just blamed my parents, as most of us teens do!

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Gene Mutations Can Mean Longer Life March 4, 2008

Posted by Mrs Weird Scientist in Genetics, Human Body, Tough Stuff.
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While they won’t make someone live forever, researchers recently identified some variations in genes that can allow people to live longer. Your genes are your special and unique instructions that determine things like your hair and eye color.

Say Hello To Centenarians

Elderly Nir Barzilai and his team are from the Albert Einstein College of Medicine, which is part of Yeshiva University in New York. Their work involved research subjects of Ashkenazi Jewish descent who were all 100 years of age or older. The fancy term we like to use for people in this age bracket is centenarian. Barzilai and his colleagues identified two gene mutations in the centenarians. If you’re a keen bean, you can read the full, more technical version in the Proceedings of the National Academy of Sciences.

Mutations Can Be Good

You might be wondering to yourself that it seems odd for a mutation to result in greater longevity – something we consider beneficial! The word mutation can leave us thinking of disease, death and just generally bad stuff. While this is often the case, genetic mutations can also lead to positive changes. It’s thought that these changes occur to help humans or other organisms evolve and better adapt to their environment.

Looking Inside The Body

DNA In this study, researchers found that the two mutations affect a receptor for insulin-like growth factor 1 (IGF-1). What does IGF-1 do? If you’re thinking it might influence growth, you’re definitely on the right track. IGF-1 is a guiding force in your body’s growth and maturity. It’s especially dominant during puberty and directs the intense growth and development that occurs during the adolescent years. So, what if the receptor stops working properly, as in the case of the centenarians? If the receptor is just a wee bit faulty, the result is that IGF-1 doesn’t effectively bind to the receptor. Low and behold, the pathway to aging and maturation doesn’t proceed at the same pace and ultimately, it is slowed.

For my male readers, don’t get too hopeful you’ve got the gene mutations. Thus far, the carriers identified are all women. Even more interesting is that the centenarians were shorter than an average woman. These women were approximately 2.5 centimeters shorter than the rest of the population. It makes sense, however, given the role of IGF-1 during the huge pubertal growth spurt.

Our Obsession

Injection In westernized societies, we’re absolutely obsessed with anti-aging and finding the next product to decrease aging – whether it’s the visible, aesthetic signs of aging or the internal, physiological ones. Ironically, people have been getting injections of growth hormone for many years now, with the belief that it slows down the aging process. Given that Barzilai’s study showed it was the people with lower levels of growth hormone who are living longer, these injections could potentially be quite dangerous.

We’re Not Alone

Another thing to keep in mind is that humans are not the only ones with these types of mutations. Worms, flies and mice have similar faulty genes that increase longevity. In the coming years, researchers will probably be in a mad flurry to investigate the genes in other centenarian populations around the world. One of the hopes is to discover strategies to reduce aging in the general population. I guess for now though, I’ll just have to fake it by sticking with my anti-aging face cream!

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It’s Good To Look Like Poo February 22, 2008

Posted by Mrs Weird Scientist in Animals, Insects, Tough Stuff.
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Sometimes, it’s great to look like poo. That is, if you’re a caterpillar! Say hello to the Asian swallowtail caterpillar. It has some neat tricks up its sleeve to successfully stay camouflaged from predators. The first trick comes into play quite early on – when the caterpillar is black and white, with fine spines. Here, it resembles bird droppings. Later on, the caterpillars get older and grow larger, which means it’s a lot harder for the caterpillars to pass themselves off as bird poo. So, as the little critters fatten up, their color changes to a vivid green. Hmmm. Why might being green work well as a camouflage? If you guessed it’s because they can blend in with the leaves, you got it!

Caterpllar Camouflage

Credit: Ryo Futahashi. You can see the wee caterpillar on the left side of the picture looks a lot like bird droppings! On the right, the distinguished fellow is a grown caterpillar – the bright, green color really does make the caterpillar look like the surrounding leaves.

Manipulating The Caterpillar’s Camouflage

In an interesting twist of events, Ryo Futahashi and Haruhiko Fujiwara of the University of Tokyo in Japan, discovered a special way to keep the caterpillar looking like bird droppings. This means that the caterpillar still matures and develops, but it retains its poopy camouflage instead of growing into a green caterpillar that resembles leaves. How did the researchers accomplish this task? It’s not so easy.

Caterpllar Camouflage 2

It’s All About Genes

You might already be familiar with the concept of genes. Your genes are unique instructions that tell your body how to work. They control all sorts of stuff such as your hair or eye color. Humans aren’t the only ones with genes either! Caterpillar camouflage depends on genes. There are three genes that control the caterpillar’s camouflage. One is responsible for the green color, another for the black color and finally, one for those spikes we see on the very young caterpillars.

Tinkering With Genes

If researchers can find a way to meddle with these genes, they can change the caterpillar’s color. Hint hint. In the case of our Japanese scientists, they did their meddling with a hormone that rules the expression of all three genes. It’s called juvenile hormone. Researchers smeared a synthetic version of juvenile hormone on the back of a young caterpillar. Since the hormone controls the three genes that affect the caterpillar’s color, adding more of the hormone managed to keep the caterpillar looking poopy right through its development. It’s a cool manipulation because it teaches us more about how hormones and genes interact. As for all this talk about poo, I think my next blog post will be on something a bit more pleasant!

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