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

Abstract

The haemocyte reactions of the white grub larvae Polyphylla adspersa to 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 of Galleria mellonella were individually infected with monoxenic Heterorhabditis bacteriophora or Steinernema glaseri. The maximum total haemocyte counts (THC) level of the white grub larvae against the nematode S. glaseri occurred at 12 h post-injection. In addition, by 8 h post-injection, the granulocyte and plasmatocyte levels decreased. The cell reactions of the grubs against H. bacteriophora in terms of THC and differential haemocyte counts and the encapsulation rate started earlier and were more pronounced than those against S. glaseri. The maximum percentage of the encapsulation observed in the white grub larvae against S. glaseri (27.3 ± 0.7%) and H. bacteriophora (36.5 ± 3.5%) occurred at 12 and 8 h post-injection, respectively. EPN-triggered encapsulation in P. adspersa larvae was more extensive than in G. mellonella larvae.