Temporal dynamics of the encapsulation response towards a synthetic immune challenge in Acheta domesticus

Researchers interested in insect ‘ecological immunology’ often quantify variation among individuals in the capacity to produce an immune response by challenging the immune system with a synthetic implant. Many studies focus on the encapsulation response in particular, because it requires the coordination of different cellular and humoral factors. However, most encapsulation assays are based on a single assay period, in part because the assay is destructive, such that the response cannot be measured repeatedly in the same individual. This approach may be problematic. For example, if the time‐course of the response is complex, an arbitrarily chosen assay period may fail to capture the most biologically relevant parameters of the response. In the present study, the time‐course of the encapsulation response towards a synthetic, nylon implant is investigated over a 5‐day period, using Acheta domesticus as a model host. Encapsulation is quantified at intervals by randomly allocating crickets to different time‐points. The most rapid period of capsule development appears to occur during the first 6‐h period. Subsequent increases in capsule size can only be confirmed during the latter stages of the assay period, when there is also a significant increase in haemocyte density. The results indicate that, in any given system, the assay period should ideally be based on preliminary data quantifying the time‐course of the response. Such data encourage clearer conclusions regarding the biological meaning of the assay and will increase relevance for real‐host parasite systems, in which temporal dynamics can be highly variable.