Correlation of oxygen consumption, cytochrome c oxidase, and cytochrome c oxidase subunit I gene expression in the termination of larval diapause in the bamboo borer, Omphisa fuscidentalis

The moth Omphisa fuscidentalis (Lepidoptera, Pyralidae) is a univoltine insect with a larval diapause period lasting up to 9 months. We studied changes in O2 consumption in conjunction with cytochrome c oxidase activity and cytochrome c oxidase subunit I (cox1) gene expression. O2 consumption changed within a day, showing a supradian rhythm with a ca.12-h cycle at 25 °C. During the first two-thirds of the diapause period, from October to March, O2 consumption was constant until January and then increased by March. Topical application of methoprene, a juvenile hormone analog (JHA), to diapausing larvae terminated the diapause and was associated with an increase in O2 consumption rate at diapause termination. In JHA-treated larvae, cytochrome c oxidase activity in fat bodies was high at the beginning of the prepupal period and highest at pupation. cox1 expression in fat bodies displayed a transient peak 8 days after JHA application and peaked in the prepupal period. Taken together, our results show that the break of diapause by JHA is associated with the activation of cox1, bringing about an increase in cytochrome c oxidase activity, followed by an increase in O2 consumption rate.