Retention of immunolabels by Diorhabda carinulata, a biological control agent of saltcedar

Abstract

AbstractMarking biological control agents facilitates studies of dispersal and predation. This study examines the feasibility of marking the various life stages of a weed biological control agent, Diorhabda carinulata (Desbrochers) (Coleoptera: Chrysomelidae), by submersion in rabbit or chicken immunoglobulin G (IgG) protein solutions. We determined whether externally applied IgGs are effective labels of the various lifestages, whether IgGs can be retained between D. carinulata lifestages, and to what extent abiotic factors associated with field conditions mediate label retention. The presence of the labels on the various lifestages of the beetles was detected by IgG‐specific enzyme‐linked immunosorbent assays. Duration of each immunolabel was measured on eggs and larvae in laboratory studies and on adults in laboratory and field studies. For adults, both labels showed high (>80%) retention for ca. 14 days after marking under field and laboratory conditions. Temperature and type of label (rabbit or chicken) had only a minimal effect on marker retention. Externally marked eggs exhibited high (100%) retention for both proteins over the entire duration of the egg stage. Interestingly, some larvae emerging from externally labeled eggs contained both external and internal IgG marks. To our knowledge, this is the first case of an IgG being transferred from the egg to larva of an insect. Age of eggs at the time of label application affected the intensity of the external label on neonates. For instance, larvae that emerged from eggs that were >1 day old when labeled exhibited stronger label retention than larvae that emerged from eggs that were 1 day old when labeled. For larvae, retention of rabbit IgG was greater than retention of chicken IgG. Label retention declined as larvae aged; larvae >3 days old retained significantly less label than did neonate larvae. Both IgG labels were retained from the first to second instar, but at a very low rate of <10%. Overall, our study demonstrates that protein‐marking technology has potential for use in studies of dispersal and predator–prey associations for D. carinulata.