Serological marking of Pnigalio agraules (Hymenoptera: Eulophidae) for field dispersal studies

Abstract

The parasitoid wasp Pnigalio agraules (Wlk.) is a key natural enemy of the horsechestnut leafminer Cameraria ohridella Deschka and Dimic (Lepidoptera: Gracillariidae). As a basis for mark-release-recapture studies, aimed at investigating the dispersal of this parasitoid in the field, adults of P. agraules were marked using a vertebrate-specific immunoglobulin (IgG). The marker was later detected by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). The IgG was either applied externally by spraying or internally by feeding an IgG-enriched diet. Different concentrations of the marker were used and the influence of abiotic (climatic conditions, time elapsed between marking and marker examination) and biotic factors (sex and age of the parasitoids) on the detection of the immunomarker was tested. External marking by spraying led to more homogeneous labelling than feeding the marker. Parasitoids labelled with 0.25 mg rabbit IgG per ten individuals contained enough immunomarker to be easily distinguished from unmarked ones. Neither the climatic conditions nor the sex or age of the insects had an influence on the detection of the marker. The IgG remained well detectable during the entire lifespan of the parasitoids, which was not negatively affected by the marking procedure. Serological marking can be used to investigate the dispersal behaviour of beneficial insects within mark-release-recapture studies.