Action of Insecticides on the Cellular Immune Reaction of Drosophila Melanogaster Against the Parasitoid Leptopilina Boulardi

Abstract

Abstract-Drosophila larvae infested by endoparasitoids can survive the infestation by an immune reaction leading to the encapsulation and destruction of parasitoid eggs. Conversely, parasitoids can escape the encapsulation by inhibiting this immune reaction. These processes could be influenced by exposure to pesticides, so an experiment was designed to investigate this possibility. Two strains of Drosophila melanogaster Meigen were tested, one with a high capacity for encapsulation (reactive strain) and the other with a very low capacity for encapsulation (nonreactive strain). We compared their immune reaction capacity after infestation when reared on a medium containing or not containing an LD30 of insecticide. Six different insecticides were tested. Two appeared to modify the effectiveness of the immune reaction. When the reactive strain was tested, dieldrin decreased the success of the immune reaction by 25%, and endosulfan, by 23%. Endosulfan also decreased the encapsulation rate of this strain by 26%. With the nonreactive strain no effect was observed regardless of insecticide. The possible causes of these weakening of encapsulation ability and their consequences on the evolution of these species are discussed.

Mechanisms by which pesticides affect insect immunity

“…These insecticides decrease the encapsulation response in larvae of the fly, D. melanogaster, to eggs of the hymenopteran endoparasite, Leptopilina boulardi, leading to an increase in the survival rate of the parasitoid eggs (Delpuech et al, 1996). Conversely, lindane (another organochlorine), propoxur (a carbamate), oxydemeton-methyl (an organophosphate), and chlordimeform (a formamidine) have no measurable effect on encapsulation of parasitoid eggs (Delpuech et al, 1996).…”

Phylogeny, classification and evolution of the Cynipoidea

“…Rizki & Rizki 1990; van Alphen 1993; Janssen et al . 1995; Combes 1996; Delpuech et al . 1996; Carton & Nappi 1997; Gemmil & Read 1998).…”

“…Some easily cultivated Drosophila parasites have become important model organisms in experimental studies of parasitic wasp biology (e.g. Rizki & Rizki 1990;van Alphen 1993;Janssen et al 1995;Combes 1996;Delpuech et al 1996;Carton & Nappi 1997;Gemmil & Read 1998).…”

Physiological consequences of immune response by Drosophila melanogaster (Diptera: Drosophilidae) against the parasitoid Asobara tabida (Hymenoptera: Braconidae)

“…In contrast, flies in the field face a variety of environmental stresses including starvation, desiccation, attack from other parasites, as well as heat and cold shock (Van Herrewedge & David, 1997). Indeed, survivors of parasitism have much reduced stress resistance; they are less resistant to desiccation (pupal –Kraaijeveld & Van Der Wel, 1994, adult –Hoang, 2001) and starvation (adult –Hoang, 2001), have lower tolerance to chemical hazards such as pesticides (Delpuech et al ., 1996), and have an increased chance of attack by other parasitoids (Fellowes et al ., 1998b). Similar reductions in stress resistance resulting from efforts to survive parasitism have been demonstrated in other insects (Moret & Schmid‐Hempel, 2000).…”