Dehydration and infection elicit increased feeding in the western flower thrips, Frankliniella occidentalis, likely triggered by glycogen depletion

We examined water balance characteristics and influence of desiccating conditions on adult western flower thrips (Frankliniella occidentalis) physiology and behavior. Western flower thrips are globally invasive and likely to contend with shifts in water availability across their expansive geographic range. Basic water balance characteristics, including water mass and dry mass, were established for adult males and females, revealing a distinct sexual dimorphism wherein females are larger, but males retain a larger percentage of their mass as body water. Males lose relative water mass more quickly and their survival times are shorter when compared to females. RNA-seq analysis identified significant enrichment of factors associated with carbohydrate transport and metabolism in dehydrated males and females. A reduction of glycogen reserves was confirmed during dehydration. The probability of thrips feeding significantly increased when desiccation was a factor. Lastly, infection with Tomato spotted wilt orthotospovirus (TSWV), a principal plant-pathogenic virus transmitted by F. occidentalis, did not have a consistent and apparent influence on desiccation tolerance; however, a reduction in glycogen reserves, and an increase in feeding activity in infected thrips, very similar to that observed in dehydrated thrips, was observed. Our results establish the fundamental water balance characteristics of adult thrips, and indicate that dehydration significantly influences the survivorship and feeding behavior of thrips; crucial factors that contribute to their capacity to spread disease.