Does the Ingestion of Isoxaflutole Herbicide Affect the Midgut and Salivary Glands of Pentatomidae Predators?

Abstract

-Podisus nigrispinus is a generalist predator naturally occurring in agricultural and forestry systems that effectively contributes to the population balance of phytophagous insects, especially defoliating caterpillars. Histological changes were evaluated in the salivary glands and midgut of P. nigrispinus caused by ingestion of systemic herbicide isoxaflutole. These predator females were fed with leaves of eucalyptus plants, Tenebrio molitor pupae or water, contaminated or not by herbicide. Salivary glands and midguts were dissected, processed and analyzed under a light microscope. Activity level and cell morphology of the salivary glands and midgut showed differences among insects fed on plants, contaminated water or pupae. The epithelia of the salivary gland and midgut of individuals which had no contact with the herbicide showed homogeneous cytoplasm, nucleus with predominance of decondensed chromatin and evident nucleoli, intense cell activity features. As for the insects in contact with contaminated food, they presented undeveloped nucleus and condensed chromatin. The luminal contents of the salivary glands in the contaminated insects had become more acidophilus than in insects without poisoning, as well as having heterogeneous and granular secretion, being more evident in the bioassay in which the insects fed on contaminated water. There was a marked morphological change in the midgut cells in contaminated insects. High degree of apoptosis, disorganization and secretory vacuoles in the epithelial cytoplasm were observed. The apical portion of the midgut cells proved undeveloped, irregular and partially destroyed. It is concluded that isoxaflutole causes morphological changes in the digestive system of the predator P. nigrispinus.Keywords: biological control, cell apoptosis, digestive system, morphological change, Podisus nigrispinus. RESUMO -Podisus nigrispinus é um predador generalista de ocorrência natural em sistemas agrícolas e florestais que contribui de forma efetiva para o equilíbrio populacional dos insetos fitófagos, principalmente lagartas desfolhadoras. Avaliaram-se alterações histológicas nas glândulas salivares e no intestino médio de P. nigrispinus causadas após ingestão do herbicida sistêmico isoxaflutole. Fêmeas desse predador foram alimentadas com folhas de plantas de eucalipto, pupas de Tenebrio molitor ou água, contaminados ou não pelo herbicida. As glândulas salivares e o intestino médio foram dissecados, processados e analisados em microscópio de luz. O nível de atividade e a morfologia celular das glândulas salivares e do intestino médio apresentaram diferenças conforme a alimentação. Os epitélios da glândula salivar e do intestino médio de indivíduos que não tiveram contato com o herbicida apresentaram o citoplasma homogêneo, núcleos com predomínio de cromatina descondensada e nucléolos evidentes. Já os insetos que tiveram contato com o herbicida apresentaram

Spodoptera frugiperda (Noctuidae) fed on transgenic maize can transfer Bt proteins to Podisus nigrispinus (Pentatomidae)

“…Discarding cells by cell death (Santos et al, 2015) might be a response to damages to midgut epithelial cells after Bt ingestion. Infections, mutations, presence of viruses, toxic aggressions, such as insecticides or herbicides, thermal shock, ionizing radiation, among others are stimuli described as triggers of midgut cell death (Gonçalves et al, 2013;Daniel et al, 2014;Gonçalves et al, 2016). Despite the importance of apoptosis to eliminate damaged or infected cells that may affect their normal function, excessive apoptosis can impair tissue function (Portt et al, 2011;Clapp et al, 2012), affecting important digestion processes and consequently predation and survival.…”