Veerman Alfred, Veenendaal René L
Department of Population Biology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Kruislaan 320, 1098 SM Amsterdam, The Netherlands.
J Insect Physiol. 2003 Aug;49(8):727-32. doi: 10.1016/s0022-1910(03)00097-0.
In the spider mite Tetranychus urticae photoperiodic time measurement proceeds accurately in orange-red light of 580 nm and above in light/dark cycles with a period length of 20 h but not in 'natural' cycles with a period length of 24 h. To explain these results it is hypothesized that the photoperiodic clock in the spider mite is sensitive to orange-red light, but the Nanda-Hamner rhythm (a circadian rhythm with a free-running period tau of 20 h involved in the photoperiodic response) is not and consequently free runs in orange-red light. To test this hypothesis a zeitgeber was sought that could entrain the Nanda-Hamner rhythm to a 24-h cycle without inducing diapause itself, in order to manipulate the rhythm independently from the orange-red sensitive photoperiodic clock. A suitable zeitgeber was found to be a thermoperiod with a 12-h warm phase and a 12-h cold phase. Combining the thermoperiod with the long-night orange-red light/dark regime, both with a cycle length of 24 h, resulted in a high diapause incidence, although neither regime was capable of inducing diapause on its own. The conclusion is that the Nanda-Hamner rhythm is necessary for the realization of the photoperiodic response, but is not part of the photoperiodic clock, because photoperiodic time measurement takes place in orange-red light whereas the rhythm is not able to 'see' the orange-red light. It is speculated that the Nanda-Hamner rhythm is involved in the timely synthesis of a substrate for the photoperiodic clock in the spider mite.
在二斑叶螨中，光周期时间测量在波长580纳米及以上的橙红光下，于周期长度为20小时的光/暗循环中能准确进行，但在周期长度为24小时的“自然”循环中则不行。为了解释这些结果，有人提出假说，二斑叶螨的光周期时钟对橙红光敏感，但南达-哈姆纳节律（一种参与光周期反应、自由运行周期τ为20小时的昼夜节律）则不敏感，因此在橙红光下自由运行。为了验证这一假说，人们寻找了一种能够将南达-哈姆纳节律调整为24小时周期且自身不诱导滞育的授时因子，以便独立于对橙红光敏感的光周期时钟来操控该节律。结果发现，一个合适的授时因子是一个具有12小时暖期和12小时冷期的温度周期。将该温度周期与长夜间橙红光/暗循环（两者周期长度均为24小时）相结合，尽管单独一种循环都无法诱导滞育，但却导致了高滞育发生率。结论是，南达-哈姆纳节律对于光周期反应的实现是必要的，但不是光周期时钟的一部分，因为光周期时间测量在橙红光下进行，而该节律无法“感知”橙红光。据推测，南达-哈姆纳节律参与了二斑叶螨光周期时钟底物的适时合成。
