Scientists discover parasitoid wasp that attacks adult Drosophila flies

North American researchers have discovered a species of parasitoid wasp that attacks and develops inside adult flies of the genus Drosophila. This finding represents a novelty in the field of biology, since, until then, there was no record of species that parasitized the adult stage of flies, such as the widely studied Drosophila melanogaster, a key species in scientific research.

The discovery, made by a team of researchers in southeastern states of the United States, reveals that this new species of wasp, called Syntretus perlmani, infects adult flies by laying eggs inside their bodies. The wasp's life cycle includes the hatching of larvae that, when developed, emerge from the fly's abdomen, in a process that lasts about 18 days.

Parasitism in adults, known as "imagobiosis", is a rare strategy among insects, especially among parasitoid wasps. Typically, these species attack larvae or pupae of other insects. However, S. perlmani follows a distinct evolutionary line, belonging to the Euphorinae group, a subfamily of braconid wasps known for their ability to infect adults of other insects, such as beetles and ants.

Although there are records of wasps attacking adults of other insects, this is the first time that this behavior has been observed in flies of the genus Drosophila. This expands our understanding of the biodiversity and specialization of parasitoid wasps, opening up new possibilities for studying how these organisms evolve to face the challenges of infecting adult hosts, which tend to be more mobile and resistant than their juvenile forms.

Drosophila melanogaster has been one of the main model species in genetic and biological studies for over a century. Therefore, the discovery of a wasp that parasitizes it in its adult stage could have profound implications for future research, especially in understanding host-parasite interactions, immunity, metabolism and behavior. According to the researchers, the fact that S. perlmani using such a widely studied species as a host may provide new insights into immunological and ecological mechanisms.

Furthermore, the new parasitoid wasp can aid in studies on the evolution of immune responses at different stages of insect development. As D. melanogaster It is a species that is easy to genetically manipulate, which allows controlled experiments on how these insects react to attacks by adult parasitoids.

Geographical distribution and frequency of infection

The new wasp species was collected in fruit-baited traps in rural and suburban environments. Infections by S. perlmani were observed in less than 1% of males of the species Drosophila affinis, collected between March 2023 and February 2024. Although the infection rate is low, scientists point out that it varies throughout the year and according to the abundance of hosts.

By analyzing DNA samples from wild flies, researchers also found signs of S. perlmani in flies D. melanogaster captured in the states of Georgia, Virginia, Pennsylvania and Illinois. This suggests that the wasp may have a wider distribution than initially thought, with the possibility of parasitizing several species of Drosophila.

More information can be found at doi.org/10.1038/s41586-024-07919-7