FABI PhD candidate Quentin Guignard recently returned from a three week visit to the University of Würzburg in Germany where he received training to operate an electroretinogram (ERG). He visited the lab of Prof. Johannes Spaethe and Dr Martin Strube-Bloss, both world-leaders in the field of neurology and physiology of insects’ perception of their environment. His trip was made possible through an Entomological Society of Southern Africa (ESSA) Young Entomologist Travel Grant that Quentin was awarded. This equipment is needed as part of his PhD project to link the protein expressed in the compound eye to colour vision and the visual spectrum visible to the European woodwasp, Sirex noctilio.

Quentin explains that the basis of colour vision in insects, and in the rest of the animal kingdom, is strongly linked to the presence of proteins called opsins. Different opsins cause photons of different wavelengths (colours) to be absorbed by the photosensitive cell, and lead to a depolarisation. A common way to link the range of the visual spectrum each opsin can absorb is to perform an ERG study. This entails inserting an electrode into the eye of the insect and then flash it with different wavelengths (colours) of light. For each wavelength flashed (17 in this experiment), the corresponding depolarisation can be recorded and transformed as the sensitivity to the different wavelength.

The outcome was fascinating. Quentin was able to accurately link the UV opsin peak at λmax= 363nm, and the green opsin peak at λmax= 520-527nm from the compound eyes of S. noctilio. There was no physiological evidence for a blue opsin peak which corresponds with the genetic data previously investigated. Apart from the data, the various discussions and advice from Johannes and Martin was very valuable for the rest of his project. The experience and understanding of running an ERG system would also be valuable for the rest of his career. Quentin will present a seminar on ERG for those that want to find out more about this technique.