Redox chemistry behind dragonfly romance

A mature Sympetrum darwinianums

The colourful displays that male animals use to attract a mate are a common feature of the animal kingdom but the display that some male dragonflies makes is slightly special – they turn from a dull yellow to bright red to signify sexual maturity.

Ryo Futahashi and colleagues at the National Institute of Advanced Industrial Science and Technology in Japan, have now shown that that colour change is down to simple reduction chemistry.

By extracting the pigments in mature and juvenile male dragonflies, they found that the two groups both used the same basic pigments – xanthommatin and decarboxylated xanthommatin – but that the difference comes from the oxidation state of the pigments. While immature dragonflies contain the oxidised form of these pigments, giving them a yellow colour, the adult males contained the reduced form, giving them their characteristic red colour.

Published in Proceedings of the National Academies of Science, USA , the team also showed that young dragonflies, injected with a reducing agent, turned red before their time. This is the first example of a redox controlled colour change in animals.