Consumption of polypropylene caused some ultrastructural and physiological changes in some tissues of Galleria mellonella (Lepidoptera: Pyralidae) larvae

Abstract

G. mellonella is a promising species for use in the biodegradation of plastics. It is easy to breed and has high resistance to diverse climatic conditions, which is particularly valuable when considering its potential application in the decomposition of plastics. Thus, it demonstrated the capacity for biodegradation of the most common types of plastics, such as polyethylene (PE) and polypropylene (PP). However, reports on whether consumed plastics or their decomposition products will adversely affect the structure and functioning of the internal organs are rather poor. The studies aimed to determine whether the consumption of PP by a greater wax moth larvae caused any ultrastructural changes in the organs of the animal’s body, evaluate the survival rate of the animals, and describe their reproduction. Thus, this study provided an understanding of histological and ultrastructural changes caused, or not caused, by the PP diet. We investigated three organs – midgut, silk gland, and fat body – under PP consumption by G. mellonella caterpillars (7th instar larvae). The level of reactive oxygen species (ROS) in selected organs, as well as the ability of larvae to survive and undergo metamorphosis were also examined. The animals were divided into four groups: G0-C, G0-S, G0-24, and G0-48. The research used transmission electron microscopy (TEM), confocal microscopy, and flow cytometry. Our study showed that a diet containing PP did not affect internal organs at the ultrastructural level. Cells in the analyzed organs – midgut, silk gland, and fat body – showed no degenerative changes. An increase in the intensity of autophagy and cell vacuolization was noted, but they probably act as a survival pathway. These observations suggest that the final larval stage of the greater wax moth can potentially be applied in PP biodegradation.

Keywords

• Polypropylene biodegradation
• ultrastructure
• midgut
• fat body
• autophagy
• cell vacuolization