|Chironomus plumosus male|
Welcome to episode 2 of the series Larva Thursday on this blog. Today we will be looking at the non-biting midges - the Chironomidae, a family of nematoceran flies comprising of perhaps some 10000 species.
Chironomidae are important as indicator organisms. Their presence, absence, or quantities of various species in a body of water can indicate whether pollutants are present. Larval stages of them can be found in almost any aquatic habitat in which they usually form an important fraction of the macro zoobenthos.
However they are notoriously difficult to identify and ecologists often record them only by species groups. Each morphologically distinct group comprises a number of morphologically similar species that can only be further identified by rearing adult males or by cytogenetic analysis of the polytene chromosomes. Morphology-based identification of females is often impossible. Hence, environmental assessments and bio-monitoring of freshwater habitats have much to gain if the larvae and other life history stages could be more readily identified to species. The use of DNA Barcoding seems to be a logical consequence and indeed it has been used in a number of studies. Researchers were able to conduct biodiversity assessments that included females and to describe hitherto undescribed larval stages of some species. New species were discovered and described for Brazil, Norway, and Tibet.
All studies show that a DNA Barcode library for chironomids is very useful for species identification especially the larval stages that serve so well as environmental indicators. As effective and rapid identification is essential for the success of modern freshwater bio-monitoring projects, DNA Barcoding represents a powerful tool to do exactly this.