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.
biological control; cell apoptosis; digestive system; morphological change; Podisus nigrispinus
A. Salivary gland of insects fed pupae sprayed with distilled water (control) showing lumen (L), epithelium (Ep), and nucleus (arrow). Bar = 50 μm. B. Salivary gland of insects fed pupae sprayed with herbicide, showing lumen (L), epithelium (Ep), nucleus (arrow), and the granular area (*). Bar = 10 μm. C. Salivary gland of insects fed on plants sprayed with herbicide showing lumen (L), epithelium (Ep), nucleus (arrow), and the granular area (*). Bar = 10 μm. D. Salivary gland of insects fed with a commercial herbicide solution, showing lumen (L), epithelium (Ep), and nucleus (arrow). Bar = 10 μm.
A. Midgut of insects fed with distilled water (control) showing the lumen (L), epithelium (Ep), and nucleus (arrow). Bar = 50 μm. B. Midgut of insects fed with a commercial herbicide solution, showing epithelium (Ep), nucleus (arrow), and muscles (M). Bar = 10 μm. C. Midgut of insects fed pupae sprayed with herbicide, showing lumen (L), epithelium (Ep) nucleus (arrow), and vesicles (V). Bar = 50 μm. D. Midgut of insects fed on plants sprayed with herbicide, showing lumen (L), epithelium (Ep), nucleus (arrow), and vesicles (V). Bar = 50 μm.