Parâmetros imunológicos e morfofisiológicos em Spodoptera frugiperda (J.E. Smith) (Lepidoptera : Noctuidae) e Podisus nigrispinus (Dallas) (Hemiptera : Pentatomidae) expostos a CRY1AC

Abstract

Despite of the Bt formulation and transgenic Bt plants efficiency against several lepidopteran species, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) exhibits low susceptibility to the majority of them. The reasons to this low susceptibility specifically to toxins Cry1Ac and Cry1Ab are not fully clarified. Also, it is possible that species moderately or not susceptible to Cry1Ac can convey the toxin to the third trophic level. This study investigated response of S. frugiperda related to Bt with three hypotheses about its low suscepbility: regenerative cells from midgut are activated by Cry1Ac protein and renovate the epithelial cells (i) in hemolymph they increase the nitric oxide and phenoloxidases as a toxin response (ii) and the tolerance is associated to the qualitative and quantitative variations from hemocytes. We still tested the hypothesis that S. frugiperda fed with Bt-cotton can induce alterations in the ultrastructure and histochemistry of digestive cells, in humoral parameters, hemogram and ultrastructure of hemocytes of Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae), a generalist predator. It was concluded that Cry1Ac in Bt-cotton is not toxic enough to kill the armyworm, but it induce to humoral and cellular alterations as signal of response to xenobiotic. The Cry1Ac toxin ingested by S. frugiperda can expose the third trophic level (P. nigrispinus) and it causes alterations in the distribution of glycogen, lipids and calcium caused by perimicrovillar matrix disorganization. The TEM revealed the presence of spherocrystals that appear to be involved in the defense against the toxin. The humorals parameters and the hemogram of P. nigrispinus are not affected when they are reared with prey S. frugiperda fed daily with leaf Bt-cotton. However it is capable of induces little modifications in granulocytes and plasmocytes.