Cotesia flavipes (CAM) (Hymenoptera: Braconidae) supresses immune responses in Diatraea flavipennella (BOX) (Lepidoptera: Crambidae).

Eliana M Dos Passos,Valéria Wanderley-Teixeira,Fábio A Brayner,Edmilson J Marques,Álvaro A.C Teixeira

doi:10.1590/0001-3765201420130393

Eliana M Dos Passos, Valéria Wanderley-Teixeira + Show 3 more

Open Access

https://doi.org/10.1590/0001-3765201420130393

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Abstract

The present research aimed to elucidate which aspects of immune responses in Diatraea flavipennella are suppressed by the parasitoid Cotesia flavipes, thus, ensuring parasitism success. We investigated the presence of apoptosis in fat body cells through the TUNEL technique. According to the results, reduced levels of nitric oxide and phenoloxidase activity were observed in larvae parasitized for three days, and reduced total number of hemocytes, after three and seven days. An increase in plasmatocytes and decrease in spherulocytes numbers were observed in the differential count on the third day of parasitism. The number of melanized microspheres in parasitized larvae was low and indicated less intense melanization. The ultrastructural analysis confirmed the immunosuppressive effect of C. flavipes on the encapsulation response of D. flavipennella because only the formation of hemocytes capsules, adhered to the microspheres' surface, was evidenced in non-parasitized caterpillars. The effect of parasitism was also recorded on the third day with the presence of hemocytes and apoptosis in fat body cells, including aspects of degeneration in the latter. We concluded that C. flavipes suppresses cellular and humoral immunological responses in D. flavipennella and drastically affects the host's fat tissue.

Highlights

Brazil is the world's largest producer of sugarcane, generating sugar and ethanol for domestic and international markets (MAPA 2012)
The cellular and humoral responses and occurrence of apoptosis in the fat body nutritional reserve tissue in D. falvipennella that were triggered by C. flavipes parasitism, were investigated
The results of this study indicate that the endo-parasitoid C. flavipes ensures its development in D. flavipennella by suppressing the host’s cellular and humoral responses and triggering apoptosis and degradation in the fat body

Summary

Introduction

Brazil is the world's largest producer of sugarcane, generating sugar and ethanol for domestic and international markets (MAPA 2012). The Diatraea sugarcane borer complex represents one of the main problems for this culture in worldwide regions of cultivation and the biological control of Diatraea saccharalis (Fabricius) and Diatraea flavipennella (Box) occur in Brazil (Mendonça 1996). The endo-parasitoid C. flavipes was cultivated in the laboratory on D. saccharalis and introduced in Brazil in mid-1974 for the control of both borer species. A reversal predominance of the sugarcane borer species occurred in the last 30 years in the state of Alagoas in Brazil (Freitas et al 2006) showing D. flavipennella as currently the predominant species in northeastern Brazil. The D. saccharalis and D. flavipennella borers feature bio-ecological similarities; the C. flavipes wasp does not demonstrate a preference between the two hosts and is able to locate the two species (Freitas et al 2006, Silva et al 2012). Upon acceptance by the host, the immature parasitoid faces a number of physiological challenges that may diminish its chances of survival and the host’s immune defense mechanisms is the biggest challenge faced by the parasite (Edwards et al 2001)

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