Effects of the chitin synthesis inhibitor complex nikkomycin on oogenesis in the mite Tetranychus urticae

Abstract

AbstractSome effects of the chitin synthesis inhibitor complex nikkomycin on oogenesis in the two‐spotted spider mite Tetranychus urticae were demonstrated by means of electron microscopy. Four main effects were evident, depending on the oogenetic stages. Nuclear defects, observed in oogonia and primary oocytes, included a widened nuclear envelope, the intermembranous spaces of which were filled with electron‐dense material, and the occurrence of small electron‐dense agglomerations and altered nucleoli inside the nuclei. Cytoplasmic defects occurred mainly in nurse cells and involved electron‐dense granular areas accompanied by mitochondria, and large cisternae and vesicles of rough endoplasmic reticulum. Yolk synthesis in oocytes could be inhibited, as shown by the lack of yolk droplets or the presence of abnormal yolk droplets. Both phases of egg shell synthesis were disturbed, resulting in an inhibition of egg deposition. Mechanisms based upon the oogenetic effects of the metabolite complex nikkomycin are discussed.