Aquatic insects are commonly used to assess water quality, since some groups are highly sensitive to pollution, while others tolerate it. Chironomids are a group of aquatic insects that are diverse, abundant, and widely distributed in ecosystems, like streams, rivers, and lakes. The cast skins left on the surface of the water by the adult that has emerged are commonly used for these monitoring programs. However, these skins are hard to identify to species using morphological characters, such as the shape of the respiratory organ, since there are not enough comprehensive dichotomous keys.
DNA barcoding is a molecular tool that has the potential to resolve these problems by providing a rapid approach to species identification. This tool relies on a reference library of short, standardized sequences of DNA that can quickly be generated and serve as unique species identifiers, allowing users to easily differentiate species. DNA barcoding has been acknowledged by many studies (see International Barcode of Life (iBOL) for list of publications) and barcoding techniques are becoming increasingly commonplace in monitoring of aquatic systems.
Crucial for the success in the use of these molecular tools is the performance of extraction protocols, because all subsequent steps are reliant upon getting quality DNA from the specimen. Therefore, we (Petra Kranzfelder, Torbjørn Ekrem, and Elisabeth Stur) collected chironomid skins from Norway and Costa Rica and we are testing the success of different DNA extraction methods. We hope that we will be able to identify more chironomid species by improving these insect skin extraction protocols and anticipate that this work will lead to future collaborations in the area of DNA barcoding, morphological and molecular taxonomy and systematics, and chironomid life stage association and description, all of which will enhance worldwide biological monitoring. So, we hope that there is DNA in these insect skins and we will have to wait for a few months to get the answer to our question.
Written by Petra Kranzfelder (NTNU Visiting Ph.D. Fellow from the University of Minnesota)