Storing Frozen Maggots

This screwworm larva uses its tusk-like mandibles to eat the flesh of open wounds in livestock, people and pets.  A half of a century ago, these maggots caused millions of dollars in losses each year for the U.S. cattle industry.

But the threat has largely disappeared thanks to sterile-insect releases (SIR), which helped eradicate these parasites from the United States and Central America in 1966. 

The SIR programs raised huge numbers of male and female screwworm flies and then sterilized them.  When these adults were released to the wild, fly numbers dropped from fruitless mating. 

In case of future outbreaks, adult screwworm populations are maintained in cages for thousands of dollars a month.  But scientists from the Agriculture Research Service have found a way to store frozen screwworm embryos for pennies a day.

The reason adult flies are not frozen is that ice crystals can damage tissue.  In undeveloped flies, water can be removed and replaced with ethylene glycol - basically antifreeze.  This winterizing allows the embryos to be immersed in liquid nitrogen at minus 196 degrees Fahrenheit.

Researchers who need screwworms for studying can thaw the embryos and revive them using fetal bovine serum.

-- LiveScience Staff

Credit: John Kucharski