Koveos D S, Kroon A, Veerman A
Department of Pure and Applied Ecology, University of Amsterdam, The Netherlands.
J Biol Rhythms. 1993 Winter;8(4):265-82. doi: 10.1177/074873049300800401.
In the spider mite Tetranychus urticae, both diapause induction (which takes place during the larval and nymphal stages) and diapause maintenance (in the adult female) are under photoperiodic control. The question of whether or not the same photoperiodic clock is involved in both photoperiodic reactions was investigated in eight strains of the spider mite, originating from different localities in Europe. The methods employed consisted of (1) determination of the relative importance of the photophase and scotophase in the two photoperiodic reactions; (2) comparison of photoperiodic response curves for diapause induction and diapause maintenance; and (3) determination of the effect of light breaks on the capacity of long nights to maintain diapause, and comparison with the effect of light breaks in diapause induction experiments. The scotophase appeared to be much more important than the photophase for both diapause induction and diapause maintenance. In all strains the critical daylength for diapause maintenance, measured at the moment of saturation of the response to long daylengths, was identical to the critical daylength for diapause induction. However, the critical daylength for diapause maintenance appeared to be labile; it shifted gradually to shorter values as the mites were kept in the cold for a longer period of time, or were kept at a higher temperature for a progressively longer period of time after their stay in the cold room. This seems to reflect a gradual loss of photoperiodic control of diapause maintenance as diapause development proceeds. Photoperiods close to the critical daylength appeared to be less strong with regard to diapause maintenance than shorter daylengths. Quantitative differences in the "strength" of different daylengths were found in all strains investigated. Interruption of the night by short pulses of light revealed either one or two peaks of sensitivity in the night, or one broad "trough" where the two peaks had merged. However, in each case maximal sensitivity to the light breaks occurred at the same position in the night for diapause induction and diapause maintenance. The many similarities found lead to the conclusion that most probably the same photoperiodic clock mechanism is involved in both diapause induction and diapause maintenance in T. urticae.
在二斑叶螨（Tetranychus urticae）中，滞育诱导（发生在幼虫和若虫阶段）和滞育维持（在成年雌螨中）均受光周期控制。在源自欧洲不同地区的八个二斑叶螨品系中，研究了这两种光周期反应是否涉及相同的光周期时钟。所采用的方法包括：（1）确定光期和暗期在两种光周期反应中的相对重要性；（2）比较滞育诱导和滞育维持的光周期反应曲线；（3）确定光间断对长夜维持滞育能力的影响，并与滞育诱导实验中的光间断效果进行比较。对于滞育诱导和滞育维持而言，暗期似乎比光期重要得多。在所有品系中，在对长日照反应达到饱和时测得的滞育维持临界日长与滞育诱导临界日长相同。然而，滞育维持的临界日长似乎不稳定；随着螨在低温下保存的时间延长，或者在其在冷藏室停留后在较高温度下保存的时间逐渐延长，它会逐渐向较短的值偏移。这似乎反映出随着滞育发育的进行，滞育维持的光周期控制逐渐丧失。接近临界日长的光周期在滞育维持方面似乎不如较短的日长有效。在所研究的所有品系中，发现不同日长的“强度”存在定量差异。短光脉冲打断夜间会在夜间显示出一个或两个敏感峰，或者是两个峰合并后的一个宽“谷”。然而，在每种情况下，滞育诱导和滞育维持对光间断的最大敏感性都出现在夜间的同一位置。发现的诸多相似之处得出这样的结论：很可能相同的光周期时钟机制参与了二斑叶螨的滞育诱导和滞育维持。
