The infection of leafhoppers by Western X-disease virus: VI. Cytopathological interrelationships

Abstract

The lethal effect of a plant virus, peach Western X-disease virus (WXV) was investigated in a leafhopper vector, Colladonus montanus. Our earlier reports of cytopathology in trophocytes of the adipose tissue, perineurium of cephalic neural system, serous cells of the salivary glands, and alimentary tract tissue are supplemented in this paper by description of similar cytopathological signs in the mycetome, urate cells, collaterial gland, the ten remaining cell types of the salivary gland, the corpus cardiacum, pericardial cells, and connective tissue. Nonviruliferous insects were found to undergo a definite sequence of depletion of adipose tissue. The speed of depletion was reduced by viral infection, but viral “inclusions” could be found in fat cells of many stages. Whereas accumulation of densely staining basophilic material in the cytoplasm was the most typical and identifiable cytopathological symptom, a prior stage is hypothesized, characterized by nuclear hypertrophy and decreased chromaticity of cytoplasm. Cells in this stage were noted in salivary, adipose, and Malpighian tubule tissue. Extreme shrinkage or swelling of cells occurred in certain salivary acini. Systemic pathology in oviduct, alimentary tract, and possibly urate cells, could not be definitely interpreted but may have represented the onset of the moribund condition. Lesions in a particular tissue frequently occurred in apposition with lesions in a different adjacent tissue. Cephalic lesions occurred earliest on the cephalic structures first receiving hemolymph from the aorta. Insects injected with high concentrations of virus, but not transmitting WXV to celery, usually exhibited no pathology, but one anomalous case is examined in detail. Insects transmitting WXV, but living longer than other infected insects nonetheless showed severe pathological changes. Insects acquiring WXV during early life demonstrated severe pathalogy in early adulthood. Relevance of these observations to possible Mycoplasma etiology of many leafhopper-borne “yellows” plant diseases is discussed.