Geomagnetic intensity variation and deprivation elicit distinct transcriptomic responses in a migratory insect.

Geomagnetic field intensity varies along migratory routes; however, whether migratory insects respond similarly to intensity shifts and geomagnetic deprivation remains unclear. We compared transcriptomes of brown planthoppers, Nilaparvata lugens (Stål), reared under ~45 μT or ~50 μT fields, approximating intensities along their migratory route, or under a near-zero magnetic field (NZMF). The natural-range ~5 μT comparison identified 244 DEGs and a restricted functional response. 'Lipid transporter activity' was the only Gene Ontology term significant after false-discovery-rate correction, whereas 'response to light stimulus' and 'flavin adenine dinucleotide binding', both containing cryptochrome1 (Cry1), were nominally enriched. By contrast, NZMF identified 2753-3258 DEGs and enrichment of central carbon and amino-acid metabolism, peroxisomal function, redox regulation and clock-related genes. RT-qPCR validated representative genes. Given its differential expression under ecologically relevant geomagnetic intensity variation, established photoreceptive and circadian functions and previous NZMF responsiveness, Cry1 was examined by RNA interference as a step toward an eclosion-based magnetic response assay. Cry1 knockdown disrupted the diel eclosion rhythm, demonstrating its importance for eclosion timing and limiting this phenotype as a magnetic field intensity readout after knockdown. Together, natural-range geomagnetic variation and NZMF exposure may evoke qualitatively distinct magnetobiological response states rather than quantitatively different magnetic environments.