The DNA extracted from long-dead insects and other critters can shed light on their evolution, the climate of the ancient past, and other puzzles. Unfortunately, most methods used to extract DNA from these critters damages the specimens, which can hinder further studies on the specimens.
Eske Willerslev (University of Copenhagen, Denmark) and coworkers have made progress towards solving this problem. Their gentle method of DNA extraction is especially useful for extracting DNA from non-frozen specimens.
The insects.
The scientists applied their DNA extraction procedure on three types of specimens. The museum-preserved specimens were of 20 beetles stored in a museum in Denmark, and were less than 200 years old.
The frozen specimens were of 14 beetle fossils found in the permafrost of Alaska and Siberia, and were more than 10,000 years old. The specimens from sediment were of a beetle and a butterfy (soil samples, not of preserved insects), from New Zealand, and were a few thousand years old.
DNA extraction and characterization.
DNA was extracted from the specimens by immersing them in a protein-degrading buffer for up to 20 hours. Afterwards, the insects were washed in ethanol, dried, and returned to their collections.
Small amounts of DNA were obtained from this procedure. This small amount of DNA was turned into a larger amount using PCR (polymerase chain reaction), the same general technique used by law enforcement personnel to characterize blood or other useful biological fluids left behind at a crime scene.
Success of DNA extraction.
The scientists were able to extract enough DNA from all of the museum beetles. However, there was only successful DNA extraction from three of the fourteen beetles from the permafrost, and from one of the two sediment-preserved specimens.
However, there was no obvious physical damage to the insect specimens. This is a big advantage over the current destructive techniques used for DNA extraction.
For ancient specimens, destructive DNA sampling techniques may still be needed. However, for more recently deceased insects, these scientists have successfully demonstrated a method to extract their DNA without damaging the specimen.
for more information:
Thomsen, P. F.; Elias, S.; Gilbert, M. T. P.; Haile, J.;
Munch, K.; Kuzmina, S.; Froese, D. G.; Sher, A.;
Holdaway, R. N.; Willerslev, E.
Non-destructive sampling of ancient insect DNA.
PLoS ONE 2009, 4, e5048.