Virus-bearing scorpions wander the Southwest

By

Richard Harth

In the hot, arid environment of Phoenix and surrounding Sonoran Desert, ancient creatures flourish. Bark scorpions are among Earth’s oldest terrestrial animals. Their earliest fossil ancestors are believed to have made the transition from sea to land some 450 million years ago.

In new research, Arvind Varsani and colleagues in the Biodesign Center for Fundamental and Applied Microbiomics and Arizona State University’s School of Life Sciences, describe bark scorpions collected around the Phoenix area.

The venomous predators appear to play host to various polyomaviruses which, like the scorpions themselves, have ancient origins. The work was part of Kara Schmidlin’s MSc thesis with Varsani’s research group.

“A simple question emerged in the research group — what viruses are circulating in Arizona arachnids?,” Varsani says. “Soon, we were collecting scorpions in our backyards to address this question, and we identified these unique polyomaviruses.”  

The findings appear in the current issue of the journal Virology.

There are nearly 2,200 species of scorpion, belonging to the class Arachnida. Nocturnal creatures, they are generalist predators, feeding on a wide variety of insects, spiders, centipedes and even other scorpions. They are found across an impressive range of ecosystems, including deserts, grasslands, savannahs, deciduous forests, pine forests, intertidal zones, rainforests and caves.

The animal’s simple body plan consists of two primary segments, a cephalothorax — which includes four pairs of legs and pincer-bearing pedipalps — and an abdomen, which carries the tail and stinger. The pedipalps are used to capture prey, for defense, in courtship and in burrow excavation.

In the current study, four bark scorpions were collected from the Phoenix area. Three of these were found to carry polyomaviruses in their gut or liver, though the viruses produced no obvious ill effects in the scorpions. 

Polyomaviruses have circular, double-stranded DNA genomes. They were first isolated in the 1950s and given their name due to their ability to produce multiple tumors in their host organisms. Although polyomaviruses were initially identified in mammals (including humans), they have since been detected in birds and several fish species, though their diversity among arthropods has been a matter of speculation.

Careful techniques must be used to ensure an arthropod, like a scorpion, has truly been infected by a virus, as opposed to simply ingesting them from the environment or carrying them on their bodies within ectoparasites. The identification of the scorpion polyomaviruses hence remains tentative, though it is believed the viral host is either a scorpion or another arthropod.

The use of high-throughput sequencing along with traditional molecular techniques allowed the researchers to determine the genome sequences of eight novel polyomaviruses, belonging to three distinct putative virus species in the Phoenix scorpions. The study’s genomic analysis suggests that polyomaviruses and their scorpion hosts both underwent divergent evolution.

The findings are important as they suggest at least one ancestral species of polyomavirus existed among the ancient common ancestors of arthropods and Chordates — the phylum that includes humans and all other vertebrates.