Defensive tactics: lessons from Drosophila

Abstract

Parasitoid wasps exert strong selective pressure on their hosts, driving the evolution of diverse defense strategies. Drosophila, a widely studied model organism, hosts a wide range of parasites, including parasitoid wasps, and has evolved immune and behavioral mechanisms to mitigate the risk of parasitization. These defenses range from avoidance and evasion to post-infection immune responses, such as melanotic encapsulation. In response, parasitoid wasps have developed countermeasures, contributing to an ongoing arms race between host and parasite. This article reviews the anti-parasitoid behaviors of Drosophila, focusing on their role in reducing parasitization and enhancing host survival and fitness. It also explores the molecular and neuronal circuit mechanisms that underlie these behaviors, using Drosophila as an ecologically relevant model for studying host-parasitoid interactions. Furthermore, the article discusses the potential applications of these findings in biological pest control and highlights key unresolved questions in the field.

Keywords: Anti-parasitoid behaviors; Evolutionary arms race; Host-parasitoid; Innate response; Multimodal inputs; Pre-infection behaviors.

Fig. 1.

Life cycles of Drosophila and parasitoid wasps. The schematic illustrates the life cycle of Drosophila (the host, shown in grey) alongside its larval (red), pupal (dark cyan), and adult parasitoids (purple). After the wasp lays its eggs inside the host, one of two outcomes occurs: either the host's immune response halts the wasp's development through melanotic encapsulation (visible as black spots in the infected host), leading to the emergence of resistant flies (escapees), or the wasp suppresses the host's immune defenses and successfully completes its life cycle.

Fig. 2.

Anti-parasitoid behaviors of Drosophila. This schematic depicts the pre-infection behaviors displayed by Drosophila larvae and adults to defend against parasitoids, along with the sensory mechanisms that underlie these responses. For additional details, refer to the main text and Table 1.