HISTOCHEMICAL CHANGES IN MELOLONTHA MELOLONTHA (LINNAEUS) (COLEOPTERA) INFECTED BY A NEW VIRUS

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Abstract
Changes in DNA, RNA, protein, and glycogen in the fat body of a beetle, Melolontha melolontha (Linnaeus), were studied histochemically at intervals of 15, 23, 75, and 195 days after intrahemocoelic injection of a cytoplasmic polyhedrosis virus, Vagoiavirus melolonthae. As the disease progressed, the average nuclear diameter increased considerably without any apparent change in DNA content. Cytoplasmic RNA increased progressively for about 75 days and then decreased slightly. Nuclear protein content increased during the first 23 days after virus inoculation. Cytoplasmic protein content progressively increased throughout the disease process. There was no significant change in glycogen reserves 23 days after inoculation; thereafter, glycogen was drastically reduced.Three morphologically different types of cytoplasmic inclusions all staining intensely with naphthol yellow S (thus establishing their proteinaceous nature) were observed. The pyroninophilic "round" type is considered to be "mature" inclusions containing the virus particles demonstrated by electron microscopy. The resemblances between this virus and some viruses of higher animals are discussed.