Phytochemistry-Mediated Modulation of Larval Metabolism, Antioxidant Defense Systems, and Cocoon Quality Traits in Semi-Domesticated Tasar Silkworm (Antheraea Mylitta D.)

Background: The tropical tasar silkworm, Antheraea mylitta Drury (Lepidoptera: Saturniidae), is a polyphagous insect of considerable commercial importance in non-mulberry silk production. However, the physiological mechanisms by which host plant phytochemistry governs larval development, oxidative homeostasis, and eventual silk quality remain incompletely understood. Objective: This study investigated the differential effects of three primary host plants—Terminalia arjuna (Arjun), Terminalia tomentosa (Asan), and Shorea robusta (Sal)—on larval metabolic enzymes, antioxidant defense systems, and cocoon quality parameters in A. mylitta. Methods: Fourth-instar larvae were reared on each host plant for 10 days. Hemolymph and midgut tissues were analyzed for detoxification enzyme activities (CYP450, GST, CarE), antioxidant markers (SOD, CAT, GSH, ascorbate), oxidative damage (lipid peroxidation, H₂O₂), and metabolic profiles (total protein, carbohydrate, lipid). Cocoon quality was assessed by shell weight, shell ratio, and filament characteristics. Results: Larvae fed on S. robusta exhibited significantly elevated oxidative stress markers (MDA: 2.8-fold increase in midgut; H₂O₂: 210% increase) compared to T. arjuna-fed controls. Compensatory upregulation of antioxidant enzymes (SOD, CAT, GST) was observed across all treatments, with S. robusta inducing maximal responses. Detoxification enzyme activities correlated positively with foliar tannin and metal content. Cocoon quality was superior in T. arjuna-fed larvae (shell ratio: 18.4 ± 1.2%), while S. robusta produced inferior silk parameters (shell ratio: 11.2 ± 0.9%, p < 0.01). Correlation analysis revealed strong negative relationships between midgut oxidative burden and cocoon traits (r = -0.82 to -0.91). Conclusion: Host plant chemistry, particularly tannin and redox-active metal content, drives oxidative stress-mediated trade-offs between detoxification investment and silk production. These findings provide mechanistic insights for optimizing tasar silkworm rearing practices.