Infochemicals inhibited by UV

Posted on September 26, 2009

Kairomones are “infochemicals” that escape from  predators and stimulate prey species to develop improved anti-predator defence systems.  For example, predatory phantom midges (Chaoborus sp.) release a kairomone that is detected by hairs on the antennae of juvenile water fleas (Daphnia sp.), which are common prey of midges.  As a result, the water fleas develop toothed keels on their heads, which help to protect them against midge predation. 

It’s well known that ultraviolet radiation (UV) can have adverse effects on aquatic organisms, and that it alters and degrades organic substances.   It seems that this impact extends to infochemicals, because water fleas placed in water containing UV-treated kairomone extract developed keels that were less than half the normal size.  These results show that UV has the potential to affect predator-prey interactions in aquatic systems.  Plankton such as waterfleas show strong vertical migration, and  avoid the upper water layers by day.  Vertical migration can therefore help to protect prey species by ensuring that they are in contact with active kairomones, but away from the harmful effects of direct UV radiation. 

Reference:  Sterr, B.  & Sommaruga, R.  2008.  Does ultraviolet radiation alter kairomones? An experimental test with Chaoborus obscuripes and Daphnia pulex.  Journal of Plankton Research 30 (12), 1343-1350.