The present study focuses on the ability of Pterostichus melas italicus Dejean to mount cellular and humoral
immune responses against invading pathogens. Ultrastructural analyses revealed the presence of
five morphologically distinct types of hemocytes: prohemocytes, plasmatocytes, granulocytes, oenocytoids
and macrophage-like cells. Differential hemocyte counts showed that plasmatocytes and granulocytes
were the most abundant circulating cell types and plasmatocytes exhibited phagocytic activity
following the latex bead immune challenge. Macrophage-like cells were recruited after the immune
challenge to remove exhausted phagocytizing cells, apoptotic cells and melanotic capsules formed to
immobilize the latex beads. Total hemocyte counts showed a significant reduction of hemocytes after
latex bead treatment. Phenoloxidase (PO) assays revealed an increase of total PO in hemolymph after
immune system activation with lipopolysaccharide (LPS). Moreover, the LPS-stimulated hemocytes
showed increased protein expression of inducible nitric oxide synthase, indicating that the cytotoxic
action of nitric oxide was engaged in this antimicrobial collaborative response. These results provide a
knowledge base for further studies on the sensitivity of the P. melas italicus immune system to the
environmental perturbation in order to evaluate the effect of chemicals on non-target species in
agroecosystems.
