Homepage Arne Janssen, University of Amsterdam
A spider mite that manipulates plant defence
When herbivores such as spider mites attack a plant, complex plant defence mechanisms are activated.In collaboration with colleagues from the Federal Universities of Viçosa and Tocantins, Brazil, we recently discovered that certain spider mites are able to disrupt these mechanisms, effectively disarming the plant.
Phytopathogens and herbivores induce plant defences. There is evidence that some pathogens suppress these defences by interfering with signaling pathways involved in the defence, but such evidence is scarce for herbivores. We found that the invasive spider mite Tetranychus evansi suppresses the induction of signaling routes involved in induced plant defences in tomato. As a result, the mites performed much better on previously attacked plants than on non-attacked plants. These findings provide a new perspective on plant–herbivore interactions, plant protection and plant resistance to invasive species.Another mite species, the closely related T. urticae can also profit from the suppression of induction of defence by T. evansi. However, the latter protects leaf area with down-regulated plant defence by covering it with a dense web that is difficult to penetrate by T. urticae.
(photo: Jan van Arkel, IBED)
See publication in Ecology Letters
See publication in PLoS ONE
Parasitoid turns its host into a bodyguard
Parasites can induce dramatic changes of behaviour in their host species. This behaviour is thought to be detrimental to the host, but beneficial to the parasite. In a joint publication, researchers from the University of Amsterdam and University of Viçosa ( Brazil ) show evidence of spectacular behavioural changes induced by a parasitic wasp in the caterpillar of a moth species.
After the wasp (Glyptapanteles sp.) has oviposited eggs in the body of a caterpillar (Thyrinteina leucocerae), these develop into larvae that live on the body fluids of the caterpillar. After the wasp larvae crawl out of the caterpillar to pupate, the caterpillar acts as a bodyguard to defend them from predator attacks. This results in a twofold reduction of predation of the wasp pupae in the field.
After several days, the adult wasps emerge from their pupae and the caterpillar dies.
(photo Jose Lino Neto)
See publication in PLoS One
Movie of a caterpillar defending parasitoid pupae
Movie of an unparasitized caterpillar showing no response to a predator
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