Insect skins (exuviae) are of extracellular origin and shed during moulting. The skins do not contain cells or DNA themselves, but epithelial cells and other cell-based structures might accidentally attach as they are shed. This source of trace DNA can be sufficient for PCR amplification and sequencing of target genes and aid in species identification through DNA barcoding or association of unknown life stages.
Given the very low tissue content in exuviae it is rather challenging to extract sufficient quantities of DNA for further analysis. Even if one manages to end up with some DNA the question remains how pure it is and if it is actually the organism that shed the skin and not any contaminant especially from organisms that feed on the exuvia.
Colleagues from Norway put this to the test and compared the performance of five different DNA extraction methods and direct PCR in isolation of genomic DNA from chironomid pupal exuviae in terms of cost, handling time, DNA quantity, PCR success, sequence success and ability to sequence target taxa.
And the winner is:
The very low cost and handling time per sample, as well as, the lack of toxic chemicals makes QuickExtract™ the most time- and cost-efficient approach among the best performing methods tested. Cost and handling time might be of importance for studies requiring high volume DNA extraction and for instance rapid, cost-effective assembly of DNA barcodes. We would consider this extraction method for molecular studies that have large sample sizes and/or are limited in funding.