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journal1 ›› 2017, Vol. 33 ›› Issue (2/3): 319-325.DOI: 10.16409/j.cnki.2095-039x.2017.03.004

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Effect of Parasitization by Microplitis pallidipes Szepligeti on the Hemolymph Melanization, Total Number and Composition of Hemocytes in the Hemolymph of Larval Spodoptera exigua (Hübner)

JI Xiangyun, YIN Yangyi, WAN Nianfeng, JIANG Jiexian, ZHANG Hao   

  1. Institute of Eco-environmental Protection, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China
  • Received:2016-12-08 Online:2017-06-08 Published:2017-04-08

Abstract: Spodoptera exigua (Hübner) is a global insect pest that feeds on various agricultural crops including vegetables, cotton, and ornamentals. To investigate the immunological responses in S. exigua larvae parasitized by Microplitis pallidipes Szepligeti, we observed the hemolymph melanization and the changes in the total number and composition of hemocytes using a neubauer hemocytometer. The results indicated that melanization rate in the hemolymph of the early 2nd-instars parasitized by M. pallidipes began to decrease gradually from day 1 after the parasitization, the ability of the parasitic wasp in inhibiting melanization increased with time after parasitization and with increase of host age; within 5-day after parasitization, the percentage of melanization was consistently lower in the parasitized than the control group and the difference was significant during day 2 to day 6 after parasitization. The total number of hemocytes and the number of granular cells were lower in the parasitized than the control group on days 1, 2, 3 and 6 after parasitization. The changes in the number of plasmatocytes were different from that of granular cells, and the difference was significant on day 6 after parasitization compared to the control. The proportion of granular cells and plasmatocytes in the hemocytes also varied after parasitization, which was in inverse proportion to each other. In this study, we reveals that the blood cells play an important role in cellular immunity, and that the changes in the number and composition of blood cells can primarily reflect the immune response of insect cells to the parasitization of parasitoids.

Key words: Spodoptera exigua, Microplitis pallidipes, hemolymph melanization, granular cells, plasmatocyte

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