Abstracts (first author)
Predatory cannibalism in Drosophila melanogaster larvae
Predatory cannibalism involves hunting live conspecifics of size similar to (or larger than) oneself. Although this is risky and is thought to require specialized behavioural and morphological adaptations similar to those in predatory animals, instances of such predatory cannibalism have been reported in numerous non-carnivorous species. It remains unclear if such predatory cannibalism has adaptive significance, while research into its genetic and sensory basis has been hindered by the lack of a suitable model system. Here we report predatory cannibalistic behaviour in Drosophila melanogaster larvae and address its evolutionary significance. We found that groups of younger larvae regularly attack and consume larger healthy conspecific larvae. Aggregations of cannibalistic larvae are mediated by strong attraction to chemical cues from the attacked victim. The nutrition obtained through cannibalism is significant: we show that Drosophila can complete their egg-to-adult development on an exclusively cannibalistic diet, and that this diet induces phenotypic plasticity of the mouth hooks. Finally, during 118 generations of experimental evolution, replicated populations maintained under larval malnutrition evolved enhanced propensity towards cannibalism, in addition to changes in their larval-foraging path length (sitter-like behavior) and competitive ability. These results indicate that predation on conspecifics in Drosophila involves specific adaptations, has a survival value, and can rapidly evolve in response to nutritional conditions. Thus, even in non-carnivorous animals natural selection can promote cannibalistic behaviour. This discovery additionally changes the perspective on many aspects of behaviour, ecology and evolution of Drosophila and simultaneously provides an extensive model for investigating the neuronal, ecological and evolutionary aspects of cannibalistic behaviour.