Temperature and Ca²⁺ ion as modulators in cellular immunity of the Sunn pest Eurygaster integriceps Puton (Heteroptera: Scutelleridae)

Abstract

Environmental conditions in addition to divalent cations may affect the interactions between pathogens and insects. Elucidation of factors which modulate insect immune responses could be a significant part of investigations in this area. In this study, adults of Eurygaster integriceps, as the destructive pest of wheat, were kept at different temperatures in addition to injection with different concentrations of Ca2+ to find the effect on cellular immune reactions against Beauveria bassiana. Results showed that total and differentiate hemocyte numbers, nodule formation and phenoloxidase activity increased with elevation of temperature so that the higher values were obtained at 30 and 40°C at various intervals. Higher concentrations of Ca2+ ion (5 mM) caused an increase in plasmatocyte length and width especially after 60 min. Similar results were observed for nodule formation and phenoloxidase activity of E. integriceps adults after injection by B. bassiana spores and phenoloxidase activity. It is clear from the current study that thermoregulation and Ca2+ ion can positively affect the hemocyte numbers especially plasmatocytes and granulocytes, nodule formation and phenoloxidase activity in E. integriceps. The understanding of modulators of the insect immune response may directly influence novel approaches to obtain safe and effective biological control agents.

Phenoloxidase and its zymogen are required for the larval–pupal transition in Bactrocera dorsalis (Diptera: Tephritidae)

“…It is reported that divalent cations enhance or are required for phagocytosis, nodule formation, encapsulation, and other immune-related processes in insects (Zibaee et al, 2009). The effect of metal ions on PO has been extensively studied.…”

Interplay between behavioural thermoregulation and immune response in mealworms

“…Environmental temperature has been shown to affect positively the amount of PO in T. molitor being higher at 30°C than at 20 or 10°C (Catalán et al, 2012), while PO activity in Eurygaster integriceps was higher and more persistent in time at 40°C (over 72 h) than at 20 or 30°C (Zibaee et al, 2009). Moreover, field studies have confirmed that environmental temperature is positively correlated with PO activity (Fuller et al, 2011).…”

Immunological vulnerability and adjustments to environmental thermal variability

“…Previous results indicate that immune response of insects is affected by environmental temperature (Ouedraogo et al 2003, Zibaee et al 2009, Rolff & Reynolds 2009, Adamo & Lovett 2011. Par ticularly, the constitutive immune response seems to be highly sensitive to thermal conditions, being higher at elevated temperatures (Catalán et al 2012).…”