Thursday, January 22, 2015

Beetle juice

Not only the fish in the previous post, but other vertebrates, plants, and invertebrates, have antifreeze proteins that stop the growth of ice crystals inside the animal.

While fish in the Arctic and Antarctic seas need to protect themselves against temperatures of -1.9 degrees Celsius (28.5 degrees F), creatures that live on land may face colder temperatures.

the fire-coloured beetle larva -- cold-weather adventurer
photo: National Park Service
adult fire-coloured beetle
photo: Sarefo, Wikimedia

A 2012 study showed that the larva of the fire-coloured beetle is an even more efficient anti-freezer. These little grubs can withstand temperatures down to -30 degrees Celsius (-22 degrees F) because their antifreeze proteins are more active than those in cold-water fish.

This study found that the antifreeze proteins in the beetle larvae also interact with adjacent water molecules, which improves the interaction with the ice crystals and, thus, the protection against the severe cold. Do not ask me how these interactions work.

Many of these cold-tolerant insects produce high concentrations of glycerol and other kinds of alcohol molecules that slow ice formation, so although the insect freezes, its cells are not damaged.  Other chemicals (called cryoprotectants) also protect cells when freezing and when thawing.

another freezing water specialist
photo: Paul Cziko
In fact, scientists have identified a number of different types of animal antifreezes, produced by a curious and haphazard variety of species, prompting some to suggest that this adaptation occurred relatively recently, in response to sea level glaciation.

According to molecular biologist Sean Carroll, "The necessity of avoiding freezing has truly been the mother of a great number of evolutionary inventions."

Not only that, but these antifreez proteins  developed separately in Antarctic species and Arctic species (10–30 million years ago and 1–2 million years ago, respectively).  Remember, species in these two communities are isolated and don't interbreed – it's a good example of convergent evolution.

1 comment:

  1. I always wonder how these beetle managed to survive and protect themselve against that temperature. its so interesting to know about these things.

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