From predators to bloodsuckers: Comparative Venomics of horseflies (Tabanidae) across life history stages

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Venom research has provided fascinating insights into the composition and mode of action of venom cocktails of various animal groups. However, in the past, there was a bias towards studies on medically relevant groups. Also, intra-specific differences in the venom composition were only occasionally considered. In this regard, the hyper-diverse group of insects still comprises many venomous subgroups poorly studied by venom research. In addition, holometabolic insects in which larvae and adults both rely on the use of venom pose an interesting case to investigate the extent of intra-specific venom variation necessary to occupy different trophic niches. Horse flies (Tabanidae) are an especially promising model, as the predatory larvae utilize venom to overpower prey, whereas the adult females use it for the purpose of blood feeding. So far, no studies have been performed to investigate the transition of venom composition throughout an insect life cycle and, except for caterpillars, insect larvae have generally not been considered by venom research. The major goal of the proposed project is to gain insights into compositional and functional characteristics of horsefly venom throughout the life cycle of a native tabanid species. By identifying the stage-specific venom compounds I will investigate to what extent the transition from a predatory lifestyle of tabanid larvae to the blood feeding specialization of adult females is accompanied by a corresponding alteration of their venom composition. To achieve this, a comprehensive approach combining transcriptomic and proteomic workflows will be applied to reveal the genuine venom compounds of tabanid larvae and adults. In addition, several activity assays are planned with crude venom and single toxins to relate compositional and functional differences between venom of tabanid life stages.