| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2008938 | Pesticide Biochemistry and Physiology | 2016 | 8 Pages |
•Sublethal exposure to hexaflumuron changed hemocyte morphology and spreading.•Sublethal exposure altered larval haemogram profile.•Sublethal exposure caused an inhibition on phenoloxidase and nitric oxide synthase.•Sublethal exposure decreased the phagocytic ability of plasmatocytes and granulocytes.
Hemocytes circulating in the hemolymph are essential for the insect immunity to protect insects against infections. The effects of sublethal hexaflumuron exposure on the competence of hemocyte immunity of fifth-instar larvae of Mythimna separata were investigated. In this insect, the sublethal exposure could cause plasmatocyte filopodia to contract and shorten, and granulocytes to compact with a loss of cytoplasmic projections in vitro, and induce granulocytes to swell and expand in vivo. The mean number of total hemocytes was significantly declined in feed-thru larvae by 5.0 μg mL− 1 hexaflumuron. Changes in proportional counts of hemocytes showed that sublethal hexaflumuron exposure caused a decrease of granulocytes and an increase of plasmatocytes in a concentration-dependant manner, but these changes were time-dependently reduced. Few effects of the sublethal exposure were revealed on the proportional counts of spherulocytes, oenocytoids, and prohemocytes. The exposure at 24 h showed strong inhibition on phenoloxidase activity in plasma and hemocytes, but this inhibition was time-dependently weakened. The NADPH-diaphorase staining assays showed that a positive immune response of nitric oxide synthase (NOS) in hemocytes was incited by the sublethal exposure, and the longer-time exposure to the higher concentrations of hexaflumuron caused a heavier loss of NOS activity. Phagocytosis rates revealed the inhibitory effect of sublethal hexaflumuron exposure on the phagocytic ability of granulocytes and plasmatocytes that was significantly greater than the effect of chlorpyrifos at the same concentrations. These results show that sublethal hexaflumuron exposure reduces M. separata larval survival by depressing the competence of hemocyte-mediated immune responses.
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