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Spiders With Brains In Their Legs Give New Meaning To Thinking On Your Feet
Tuesday, 13 December 2011 4:13

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Smithsonian researchers report that the brains of tiny spiders are so large that they fill their body cavities and overflow into their legs. As part of ongoing research to understand how miniaturization affects brain size and behavior, researchers measured the central nervous systems of nine species of spiders, from rainforest giants to spiders smaller than the head of a pin. As the spiders get smaller, their brains get proportionally bigger, filling up more and more of their body cavities.
Nephila clavipes, a big tropical spider, has plenty of room in its body for its brain.
Credit: Pamela Belding, STRI

"The smaller the animal, the more it has to invest in its brain, which means even very tiny spiders are able to weave a web and perform other fairly complex behaviors," said William Wcislo, staff scientist at the Smithsonian Tropical Research Institute in Panama. "We discovered that the central nervous systems of the smallest spiders fill up almost 80 percent of their total body cavity, including about 25 percent of their legs."

Some of the tiniest, immature spiderlings even have deformed, bulging bodies. The bulge contains excess brain. Adults of the same species do not bulge. Brain cells can only be so small because most cells have a nucleus that contains all of the spider's genes, and that takes up space. The diameter of the nerve fibers or axons also cannot be made smaller because if they are too thin, the flow of ions that carry nerve signals is disrupted, and the signals are not transferred properly. One option is to devote more space to the nervous system.

"We suspected that the spiderlings might be mostly brain because there is a general rule for all animals, called Haller's rule, that says that as body size goes down, the proportion of the body taken up by the brain increases," said Wcislo. "Human brains only represent about 2-3 percent of our body mass. Some of the tiniest ant brains that we've measured represent about 15 percent of their biomass, and some of these spiders are much smaller."

The brains of smaller spiders, like nymphs in the genusMysmena, extend out of their body cavity into their legs.

Credit: Wcislo lab./ STRI
Brain cells use a lot of energy, so these small spiders also probably convert much of the food they consume into brain power.

The enormous biodiversity of spiders in Panama and Costa Rica made it possible for researchers to measure brain extension in spiders with a huge range of body sizes. Nephila clavipes, a rainforest giant weighs 400,000 times more than the smallest spiders in the study, nymphs of spiders in the genus Mysmena.


Contacts and sources:
Beth King
Smithsonian Tropical Research Institute

The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a unit of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Website:www.stri.org.

http://beforeitsnews.com/story/1495/...Your_Feet.html

[foltdan]

Just like many modern GOP candidates... who have their brains in their dicks!

[dolaBeetCeage]

that's very interesting.. I often wonder how much more than just instinct is going on. You know, find water, find food, stay in shadows, follow this skirting board for miles (spider miles). Behaviour is an interesting thing and if you actually look you do see it in their actions. You see planning and looking into the future a little. Nesting and protecting eggs and so on. Or do you see planning? Is it just pure mechanical instinct? I was going to say some insects are just plain dumb but spiders aren't insects. So we have these tiny jumping spiders. Proportionally they have really big heads, small bodies and powerful legs. They are kinda cheeky, not intimidated by much. I don't know if their brains would be in their legs. They do seem to have some though.

[EvaQWmrm]

Just like many modern GOP candidates... who have their brains in their dicks!

Or is it that they have dicks for brains?

[dogdesign]

The image of the giant Costa Rican spider looks just like this Golden Orb Weaver that I watched just outside my window a couple of years ago. No scale in the picture but her body was most the size of my thumb.

Seems that, by extension, the article isn't specific to spiders but extends to most (if not all) species. Saw a show recently where jellyfish with no detectable brains at all were showing remarkably sophisticated and adaptable behavior.

[gueremaisse]

Tom what level zoom/lens did you use for that shot?

[EarnestKS]

Tom what level zoom/lens did you use for that shot?

Probably using macro, zoom is not for closeups.

[MARMELADINA]

So what would happen if one of these spiders lost a leg? Would they suffer permanent brain damage?

[ApporpSothe]

So what would happen if one of these spiders lost a leg? Would they suffer permanent brain damage?

Naw,

Temporary, the brainy leg will grow back, as long as the spider does not become someones lunch.

[ENCOSEARRALIA]

Tom what level zoom/lens did you use for that shot?

Dogman got it, it's a macro, a Minolta 100mm f2.8 (link). This is the same lens that I use for my coin shots.

[aspinswramymn]

We know that many loose 3/4 of the upper part of their head and are not affected at all.....it takes some time for what they have left to become "normal" once again.......we only use 8% of our brain so that to me there is an extra 92% that we can develop for an emergency.

[BoomBully]

The more you look at GOD'S DESIGNS the more you should marvel are the wondereous works of God.

That post about the weta a few weeks back I talked about it having eyes on it's feet as well.