Effect of midgut infection with the microsporidium Endoreticulatus schubergi on carbohydrate and lipid levels in Lymantria dispar larvae

Abstract

Lymantria dispar (Lep., Lymantriidae), an important forest defoliator, is host for a variety of entomopathogenic microsporidia. These are obligate intracellular parasites that completely depend on resources provided by the hosts. The microsporidia infecting L. dispar diVer in the host tissues that become infected as well as in virulence, with presumably diVerent eVects on host physiology. Endoreticulatus schubergi infects the midgut tissue of the host; its virulence is low. We studied the eVects of infection with E. schubergi on carbohydrate and lipid levels in the L. dispar host larva. Trehalose titer in the hemolymph increased with larval age. There were no signiWcant diVerences between infected and uninfected hosts. Glycogen content of the host tissue also increased with age. Levels of this storage carbohydrate were signiWcantly lower in infected larvae at a late stage of infection when insects were either full grown larvae prior to pupation (57.4 § 5.7 and 36.4 § 5.2 g/mg in uninfected controls and infected hosts, respectively) or prepupae (53.2 § 3.4 vs. 34.7 § 4.7 g/mg). Lipid levels in host tissue likewise increased over time and were slightly but not signiWcantly lower in infected L. dispar at a late stage. The results suggest that L. dispar larvae are able to compensate for most of the loss of nurients to the developing microsporidia. DiVerences between these Wndings and the eVects of infection with the virulent microsporidium, Vairimorpha disparis, that infects the host's fat body and causes severe depletion of nutrients in L. dispar larvae are discussed.

Stuck in the Caterpillars’ Web: A Half-Century of Biocontrol Research and Application on Gregarious Lepidopteran Pests in Europe

“…Cossentine and Kuhlmann [167] noted that in the majority of its natural and colonized range, Y. malinellus populations remained neutral either by natural enemies' regulation or collaterally, due to the Btk treatments previously applied for Cydia pomonella (L.) (Tortricidae) infestations [168]. Apart from exporting BCAs, Europe contributed with susceptibility and optimization studies [160][161][162][163][164][165][166][167][168][169][170] as well as rearing records [163,[171][172][173][174]. Entomopathogenic BCAs or bioinsecticides containing living agents are hitherto not assessed in Europe.…”