Cellular reactions of the white grub larvae, Polyphylla adspersa, against entomopathogenic nematodes

Abstract

The haemocyte reactions of the white grub larvaePolyphylla adspersato entomopathogenic nematodes (EPN), together with the host haemocyte types, have been studied. Six types of identified haemocytes included the prohaemocytes, granulocytes, plasmatocytes, oenocytoids, coagulocytes and spherulocytes. The granulocytes were the dominant (65.2%) haemocyte type followed by the plasmatocytes (22.1%). Both haemocyte types encapsulate EPN. White grub larvae and last larval stage ofGalleria mellonellawere individually infected with monoxenicHeterorhabditis bacteriophoraorSteinernema glaseri. The maximum total haemocyte counts (THC) level of the white grub larvae against the nematodeS. glaserioccurred at 12 h post-injection. In addition, by 8 h post-injection, the granulocyte and plasmatocyte levels decreased. The cell reactions of the grubs againstH. bacteriophorain terms of THC and differential haemocyte counts and the encapsulation rate started earlier and were more pronounced than those againstS. glaseri. The maximum percentage of the encapsulation observed in the white grub larvae againstS. glaseri(27.3 ± 0.7%) andH. bacteriophora(36.5 ± 3.5%) occurred at 12 and 8 h post-injection, respectively. EPN-triggered encapsulation inP. adspersalarvae was more extensive than inG. mellonellalarvae.