Late ain’t great: Consequences to delayed symbiont acquisition in a leaf-footed bug

Nutritional microbial symbionts synthesize nutrients lacking in the diet of their insect host. These associations have frequently resulted in strategies that ensure symbiont transmission between host generations with high fidelity. In contrast, in several bug families, including in leaf-footed bugs (Hemiptera: Coreidae) such as Leptoglossus zonatus, an arboreal pest of pomegranates, almonds and pistachios, nymphs ingest their bacterial symbiont Caballeronia from the environment early in the second instar. Caballeronia acquisition is critical for L. zonatus; aposymbiotic bugs rarely reach adulthood, and when they do are ~50% the weight of infected adults. Caballeronia is in both soil and in host frass, but we have found access to these sources may be limited in the tree canopy. We know that a bug that is aposymbiotic is severely compromised. We asked: Does a delay in symbiont acquisition also affects adult fitness and survivorship? A cohort of L. zonatus were given no Caballeronia (negative control) or fed GFP-labelled Caballeronia at 0 (positive control), 4, 8, 12, 16, 20, or 24 days after reaching the second instar. Development time was recorded for each insect and fresh weight was collected for those that reached adulthood. We observed significant increases in development time when symbiont acquisition occurred four or more days after reaching the second instar. Adult weight declined significantly for bugs that acquired the symbiont after 16 days. Together these data suggest the window for acquisition of the symbiont is relatively narrow and has significant consequences for bug fitness should the window be missed.