Comparison of the immune response of Galleria mellonella and Rhynchophorus ferrugineus after infection with the entomopathogenic nematode Steinernema carpocapsae

The red palm weevil, Rhynchophorus ferrugineus (Olivier 1790) (Coleoptera: Curculionidae), a pest of palm trees, and Galleria mellonella L. (Lepidoptera: Pyralidae), a pest of beehives, were used as models to deepen our understanding of the host-entomopathogenic nematode relationship. The effects of the entomopathogenic nematode Steinernema carpocapsae (Nematoda: Steinernematidae) on the immune activity of R. ferrugineus and G. mellonella larvae were compared. The ability to complete the life cycle of S. carpocapsae in the two insects was also evaluated. Although S. carpocapsae is effective in the biological control of the red weevil, it is not able to complete its cycle within the host, whereas the same nematode successfully reproduces in G. mellonella. On the basis of previous laboratory data and a systematic literature review, the nematode-induced effects on the immune response of the Coleoptera and the Lepidoptera were compared. In particular, the immunocompetent haemocyte population (number and cell types), the activity of the prophenoloxidase- phenoloxidase system (proPO) and finally the inhibition and proliferation of the Gram-negative symbiont bacterium Xenorhabdus nematophila (Enterobacteraceae) were analysed.