[01] Shigeru Kikukawa, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [02] Yuta Kakihara, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [03] Hiroki Nakamura, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [04] Ayumu Saitoh, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [05] Renpei Shindou, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [06] Naoyuki Sugino, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [07] Kosuke Terayama, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [08] Jinnai Tsunekawa, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan.

The interacting effects of photoperiod and thermoperiod with different phase angles on the adult eclosion rhythm of the Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae), are investigated. The photoperiod is LD 12:12 h (L=light and D=dark) and the thermoperiods (TC 12:12 h where T=thermophase and C=cryophase) are 30°C/20°C, 28.5°C/21.5°C, 28°C/22°C, 27.5°C/22.5°C, 26.5°C/23.5°C and 25.5°C/24.5°C. For each temperature cycle, the average temperature is 25°C. When the photoperiod is superimposed on to the thermoperiod of 30°C/20°C, the temporal position of the adult eclosion peak (φ_E) is within the thermophase (30°C) regardless of the LD cycle. However, when the thermoperiod is 25.5°C/24.5°C, φ_E occurs at approximately Zeitgeber time (Zt) 3.3 after the light-on signal, regardless of the phase difference between photoperiod and thermoperiod. For the thermocycles of 28.5°C/21.5°C - 26.5°C/23.5°C, intermediate responses are observed. When 27.5°C/22.5°C is coupled with LD 12:12 h and the phase angle is changed, a phase jump of φ_E occurs at 12-16 h after light-on of the phase difference between LD cycle and TC cycle. This strongly indicates that at least two components of the time-keeping system are involved in determining the temporal position of φ_E. Thermocycle, therefore, appears to be a useful tool for analyzing temporal organization of the adult eclosion rhythm of this insect species.

Adult Eclosion Rhythm, Indian Meal Moth, Photoperiod, Thermoperiod

[01] Beck, S. D. (1980) Insect Photoperiodism, 2^nd edn. Academic Press, New York. [02] Saunders, D. S. (2002) Insect Clocks, 3^rd edn. Elsevier, the Netherlands. [03] Pittendrigh, C. S. and Bruce, V. G. (1959) Daily rhythms as coupled oscillator systems and their relation to thermoperiodism and photoperiodism. In Photoperiodism and related Phenomena in Plants and Animals (Ed. by Withrow, R. B.). American Association for the Advancement of Science, Washington, pp. 475-505. [04] Pittendrigh, C. S. (1960) Circadian rhythms and the circadian organization of living systems. Cold Spring Harbor Symposia on Quantitative Biology, 25: 159-183. [05] Arai, T. (1976) Effects of temperature and light-dark cycles on the diel rhythm of emergence in the oriental fruit fly, Dacus dorsalis Hendel (Diptera: Trypetidae). Japanese Journal of Applied Entomology and Zoology, 20: 69-76 (in Japanese). [06] Zdarek, J. and Denlinger, D. L. (1995) Changes in temperature, not photoperiod, control the pattern of adult eclosion in the tsetse, Glossina morsitans. Physiological Entomology, 20: 362-366. [07] Watari, Y. and Tanaka, K. (2010) Interacting effect of thermoperiod and photoperiod on the eclosion rhythm in the onion fly, Delia antiqua supports the two-oscillator model. Journal of Insect Physiology, 56:1192-1197. [08] Kikukawa, S., Hashizume, R., Inoue, Y., Miyabayashi, M., Mori, N., Sakata, R. and Takigaura, Y. (2015) Free-running eclosion rhythm of adult Plodia interpunctella entrained by either a single light pulse or a thermocycle. International Journal of Animal Biology, 1:281-285. [09] Kikukawa, S., Hashizume, R., Honda, M., Inoue, Y., Maekawa, T., Miyabayashi, M., Mori, N., Sakata, R., Takahashi, N., Takigaura, Y., Tanaka, K. and Uchida, Y. (2012) Effects of photoperiod and temperature on the rhythm and free-running of adult eclosion in the Indian meal moth Plodia interpunctella. Physiological Entomology, 37:258-265. [10] Kikukawa, S., Hashizume, R., Honda, M., Inoue, Y., Maekawa, T., Sakata, R., Takahashi, N., Tanaka, K. and Uchida, Y. (2013) Adult eclosion rhythm of the Indian meal moth Plodia interpunctella: response to various thermocycles with different means and amplitudes. Physiological Entomology, 38:253-259. [11] Kikukawa, S., Kakihara, Y., Nakamura, H., Okano, Y., Saitoh, A., Shindou, R., Sugino, N., Terayama, K., Tsunekawa, J., Yasui, A. and Yoneda, K. (2016) Adult eclosion rhythm of Plodia interpunctella under non-24 h photoperiods. International Journal of Animal Biology, 2:11-18. [12] Kikukawa, S., Kakihara, Y., Okano, Y., Shindou, R., Sugino, N., Tsunekawa, J., Yasui, A. and Yoneda, K. (2015) Eclosion rhythm of Plodia interpunctella under non-24 h thermocycles. International Journal of Animal Biology, 1:273-280. [13] Masaki, S. and Kikukawa, S. (1981) The diapause clock in a moth: response to temperature signals. Biological Clocks in Seasonal Reproductive Cycles (Ed. by B. K. Follett), pp. 101-112. J. Wright & Sons, U.K. [14] Kikukawa, S. and Masaki, S. (1984) Interacting effects of photophase and scotophase on the diapause response of the Indian meal moth, Plodia interpunctella. Journal of Insect Physiology, 30:919-925.