Effects of Metarhizium anisopliae crude toxins on Algedonia coclesalis larvae hemocytes
The effects of Metarhizium anisopliae crude toxins on Algedonia coclesalis larvae hemocytes were investigated by determining the insecticidal potency of different concentrations(200,500,1 000,2 000,and 5 000 mg·L-1)of the crude toxins against A.coclesalis larvae.Changes in hemocyte counts and morphologies were then assessed in A.coclesalis larvae,which were fed M.anisopliae crude toxins at 5 000 mg·L-1 concentration.Cumulative collective mortality after feeding 4 to 5 instar larvae for 9 days with 5 000 mg·L-1 M.anisopliae crude toxins using the leaf dipping method was 97.37%,and the LT50 was 3.91 days.After feeding on crude toxins,the total hemocyte concentration in A.coclesalis larvae first increased,then decreased with extended treatment time,displaying a maximum value of 5.92×106 pcs·mL-1 when the duration of treatment reached 2.0 d,significantly higher than that of the control(P<0.01).Among the hemocytes,the concentrations of granulocytes and plasmatocytes showed increasing,followed by decreasing trends with prolonged treatment time.Both reached their respective maximum values(26.99×105 pcs·mL-1 and 22.85×105 pcs·mL-1)when the duration of treatment reached 2.0 d.These values were significantly higher than that of the control(P<0.01);prohaemocytes and spherulocytes reached their maximum densities when duration of treatment reached 1.5 d and 2.0 d,respectively significantly higher than that of the control(P<0.01)then rapidly decreased.Oenocytoid concentration showed a decreasing trend with prolonged treatment time.Our analyses of the proportions of various types of hemocytes in the larvae of A.coclesalis after feeding on M.anisopliae crude toxins revealed a rather high proportion of granulocytes,ranging from 42.1%to 47.9%.The proportion of plasmatocytes increased significantly with prolonged treatment time to 39.9%at 3.5 d(P<0.05).Microscopic observation revealed ruptured,vacuo lated hemocytes that exuded their contents when A.coclesalis larvae fed on the crude toxins for 2.0 d.Collectively,M.anisopliae crude toxins exhibited strong toxicity against A.coclesalis larvae,exerting a huge impact on hemocyte concentration and hemocyte morphology within 2-3 days.
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