Flaviruses are arthropod viruses and some of them cause serious human diseases, such denque, yellow fever, Zika virus disease, and tick-borne encephalitis. However, majority of the flaviruses are harmless to humans. The viruses were found infecting glow-worms on two separate years, which suggests that these viruses are part of a glow-worm microbiome and thus they are not normally pathogenic to the insect.
As viruses usually transfer from one individual to another, we hypothesise that the glow-worms would have abnormally small amount of viruses because they are unsocial insect species: they meet each other only during mating. However, we were wrong: the glow-worms have a normal number of virus species (Figure 1). How are the viruses transmitted to the glow-worms? Since glow-worms eat slugs and molluscs, the viruses could be transmitted from their prey. Viruses can also infect gametes and then transfer from parent to offspring. Our results indicate that most of the glow-worm viruses are indeed “inherited” from a parent, which is an excellent strategy for viruses that infect unsocial host.
Glow-worms are best known for their bioluminescence. We do not yet know whether the viruses affect females’ ability to produce light or males’ ability to detect it. However, couple of the males we studied had extremely high amounts of virus in their heads (e.g. almost half of the RNA originated from a virus), so at least for these males viruses made it very difficult to detect the female glow.
On average, the glow-worms had seven different virus species. Each virus may have thousands of copies in an insect.
Viljakainen, L., Borshagovski AM., Saarenpää S., Kaitala A., Jurvansuu J. Identification and characterisation of common glow-worm RNA viruses, Virus Genes 2019. DOI: 10.1007/s11262-019-01724-5
Main photo: Glowing female glow-worm in nature. Photo: Antti Yrjölä
Last updated: 3.1.2020