Cool Creepy Crawlies

Jared lent me his copy of the Lonely Planet's guide to New Zealand, since I will be visiting this country after our stay in Australia has ended. While flipping through last night I came upon the "wildlife" section and promptly began reading. There were lots of entries about cute marsupials and several kinds of short, fat birds that are no good at flying or getting away from even the most inept of predators. Everything that was cool-looking was either endangered or threatened. It seemed a miracle that New Zealand had any native animals at all.

I looked in vain for an "Insects" section. Instead I was affronted with section entitled "Creepy Crawlies" that spoke of but one true insect, the weta. Putting aside the the derogatory term "Creepy Crawlies" for a moment, the embarrassingly ignorant authors of this guide did chose to highlight what is probably one of the coolest insects in New Zealand when they selected the weta.

The weta is nothing fancy to look at. There are apparently 70 species of weta in New Zealand, and none of them are pretty. They look a lot like crickets that have taken to the life of a couch potato, their brown cuticle bulging with an excess of snickers bars and pork rinds. Their large heads are armed with impressive jaws and sometimes tusks. They are not known for their good natured personalities. The weta's great claim to fame is two-fold. One - the NZ-based special-effects company responsible for a great deal of the awesomeness of Lord of the Rings movies took this humble NZ insect as its namesake, calling themselves "The Weta Workshop." This was long before anyone in the world outside of New Zealand knew what a weta was, much less its other claim to fame - one species of weta survives being frozen solid for hours at a time.

Now, being frozen at -9°C (that's 16°F) —85% of your body's water in the form of ice crystals, all of your tissues experiencing severe osmotic shrinkage— is ordinarily considered lethal. The alpine weta (Hemideina maori) takes it in stride. There is no larger insect that can withstand becoming a popsicle like this¹.

The way the alpine weta does it is not the way that we would expect. Other cold-tolerant species avoid turning into insect-sicles by infusing their blood with a sort of antifreeze. Just like the antifreeze in your radiator, proteins circulating in their bodies keep them liquid even under freezing conditions. They do this because ice crystals tend to be bad for living things the same way that putting a coke can in the freezer is bad for the coke can. As the ice crystals form, the coke (like every cell in your body) expands then explodes.

Antifreeze is a great strategy if it doesn't get too cold. But where the alpine weta lives it gets pretty chilly. So instead of preventing ice crystal formation in their bodies like many other insects, the alpine weta welcomes ice crystal formation. Their blood contains ice-nucleating agents, which act like seed crystals for the ice to start to form. The alpine weta compartmentalizes these ice-nucleating agents outside of its cells, allowing ice crystals to form slowly and at a safe distance from their sensitive cells. Thus the whole insect slowly freezes into a solid block of weta, but retains life, ready to scurry away as soon as warmer temperatures allow it to thaw.

I am not looking forward to the winter that awaits me in the southern hemisphere. It seems less terrible when I think about the alpine weta and thank God he decided to make us warm-blooded creatures. The weta withstands the shock of new challenges by welcoming change, a lesson even us endotherms could use. Nevertheless, I wouldn't like to be an alpine weta. I think I would be very un-weta-like if my body temperature sunk to that of my surrounding environment, ice crystals forming throughout my veins. I would probably thrash and shiver, breaking my fragile frozen exoskeleton instead of quietly enduring the freezing process. Though if I had to be a weta, I don't think I'd mind having a nice pair of tusks.

1. Ramløv, H., Bedford, J., Leader, J. 1992. Freezing Tolerance of the New Zealand Apline Weta, Hemideina maori Hutton (Orthoptera: Stenopelmatidae). J. Therm. Biol. 17(1): 51-54.

Photo by Flickr user Kiwi Mikex licensed under Creative Commons Attribution-NoDerivs 2.0 Generic License.