Covert infection with an RNA virus affects medfly fitness and the interaction with its natural parasitoid Aganaspis daci

With the advent of high-throughput sequencing, large sets of insect-infecting RNA viruses producing apparent asymptomatic infections are being discovered. In the Mediterranean fruit fly (medfly) Ceratitis capitata, an agricultural key pest of a wide range of fruits, 13 different RNA viruses have been described so far. Recent analysis demonstrated a wide distribution of these viruses in different medfly strains collected worldwide, but little is known about the interactions between those viruses and the medfly host. Previous studies suggested that a higher abundance of Ceratitis capitata nora virus (CcaNV) correlated with a shorter lifespan in adults. Here, we investigated the effect of CcaNV on a broad range of parameters related to host fitness and its interaction with other trophic levels. CcaNV purified from a naturally infected medfly strain was added to the larval diet. Pupal weight, adult emergence, flying ability, and longevity were monitored after oral infections. Our results revealed detrimental effects associated with a CcaNV infection in the medfly, in terms of reduced pupal weight and reduced adult longevity. Moreover, we tested the influence of a CcaNV infection in medflies on the parasitism performance of Aganaspis daci, an endoparasitoid used in biological control programs against medflies. Our results showed that A. daci progeny increased when parasitizing on CcaNV-infected larvae. Overall, we proved that covert RNA viruses can impact the insect ecology, directly affecting its insect host biology and indirectly influencing multitrophic interactions.

Automated summary

With the development of high-throughput sequencing, numerous asymptomatic insect-infecting RNA viruses have been found. This study focused on the interaction between Ceratitis capitata nora virus (CcaNV) and its medfly host, as well as the influence of CcaNV on multitrophic interactions. It was found that CcaNV infection in medflies resulted in reduced pupal weight and decreased adult longevity, while enhancing the parasitism performance of the endoparasitoid Aganaspis daci. These findings demonstrate the impact of covert RNA viruses on insect biology and ecological interactions.