The effect of thermal stresses on the immune system of the potato tuber moth, Phthorimaea operculella (Lepidoptera: Gelechiidae)

Abstract

The hemocytes of insects are one of important components of immune system of insects against various stresses such as pathogens attack, parasitoids, starvation period and temperature changes. Hemocytes characteristics recognition and frequency in cellular immune studies will help us in order to better pest control. In this study hemocytes of fourth instar larvae of potato tuber moth Phthorimaea operculella (Zeller)were identified after staining with Giemsa and by light microscopy at 40x magnification. Five types of identified hemocytes were prohemocytes (PRs), plasmatocytes (PLs), granulocytes (GRs), oenocytoids (OEs) and spherulocytes (SPs). The effect of different thermal stresses was also investigated for 24 hours on cellular defense of fourth instar larvae. In addition number of various hemocytes and total number of blood cells were investigated. At 35 °C, total hemocyte count (THC) and PLs of larvae was increased significantly compared to the control (25±1 °C). Also, chill stress (4 °C) showed a significant decrease in THC, PLs and OEs compared to the control. These findings could be used as a base for further investigation on the immunology studies of potato tuber moth.

Keywords

• phthorimaea operculella
• hemocytes
• cellular defense
• heat and chill stresses
• total hemocyte count