The Physiological Effects of Reynoutria japonica Houtt. (Japanese Knotweed) Root Material in Zophobas morio (Superworms)
Document Type
Event
Faculty Mentor
Joseph Staples
Abstract
Reynoutria japonica Houtt. (Japanese Knotweed) is a common invasive plant in New England. This plant thrives as an invasive due to low herbivory by native species, likely due in part to chemically mediated defenses, including emodin and resveratrol. In this study, we examine the metabolic costs of herbivorous insects consuming knotweed-derived compounds by measuring respiratory quotient (RQ; CO₂ production/O₂ consumption) in Zophobas morio; Coleoptera: Tenebrionidae (Superworms) larvae. Respiratory measurements followed a 24-h exposure to wheat-flour diets treated with knotweed root extract, commercial knotweed powder, purified emodin (60 mg g⁻¹), or resveratrol (120 mg g⁻¹). RQ differed significantly among treatments. The emodin treatment produced the largest increase relative to controls, thereby indicating a shift from lipid-based metabolic substrate to carbohydrate utilization or lipogenesis. This trend is seen in organisms under metabolic stress. Based on our results and related published studies, we suggest that in dense stands of R. japonica and other chemically defended invasive plants, metabolically costly responses may not only reduce individual insect performance but may also scale up to influence insect populations and the ecosystem functions they support.
The Physiological Effects of Reynoutria japonica Houtt. (Japanese Knotweed) Root Material in Zophobas morio (Superworms)
Reynoutria japonica Houtt. (Japanese Knotweed) is a common invasive plant in New England. This plant thrives as an invasive due to low herbivory by native species, likely due in part to chemically mediated defenses, including emodin and resveratrol. In this study, we examine the metabolic costs of herbivorous insects consuming knotweed-derived compounds by measuring respiratory quotient (RQ; CO₂ production/O₂ consumption) in Zophobas morio; Coleoptera: Tenebrionidae (Superworms) larvae. Respiratory measurements followed a 24-h exposure to wheat-flour diets treated with knotweed root extract, commercial knotweed powder, purified emodin (60 mg g⁻¹), or resveratrol (120 mg g⁻¹). RQ differed significantly among treatments. The emodin treatment produced the largest increase relative to controls, thereby indicating a shift from lipid-based metabolic substrate to carbohydrate utilization or lipogenesis. This trend is seen in organisms under metabolic stress. Based on our results and related published studies, we suggest that in dense stands of R. japonica and other chemically defended invasive plants, metabolically costly responses may not only reduce individual insect performance but may also scale up to influence insect populations and the ecosystem functions they support.
