Pathology of Spiroplasma floricola in Galleria mellonella larvae

Spiroplasma floricola strain 23-6, originally isolated from tulip tree flowers, was injected into larvae of the greater wax moth. Histopathology and cytopathology of disease larvae were studied by histochemical, fluorescent antibody, and electron microscopical methods. The gut was empty, polysaccharides in fat and muscle tissue were reduced, the fat body was broken down, and phospholipids were depleted in larvae 4 days after injection. Fluorescein conjugated S. floricola antibody was adsorbed onto hemocytes, sarcolemma, gut epithelial membrane, and the cortex of the ventral ganglia. By electron microscopy, spiroplasmas were found in hemocoel, hemocytes, pericardial cells, connective tissues, basement membranes, epidermal cells of the cuticle, the neural lamella, and the peripheral glial cells of the ventral nerve cord, and on midgut and epidermal membranes. It is postulated that the cytopathological effects induced in the body of the insect released nutritional elements that allow extensive reproduction of S. floricola.