Prey species can respond to the presence of predators by inducing phenotypic plastic traits which form morphological, life history or behavioral defenses. These so-called inducible defenses have evolved within a cost-benefit framework. They are only formed when they are needed, and costs associated with defenses are saved when predators are not present. However, a disadvantage compared to permanent defenses are lag phases between predator perception and the full formation of defenses. This may be especially important when the predation risk persists for longer periods, e.g., outlasts one generation and challenges prey offspring. We hypothesized that transgenerational induced phenotypic plasticity reduces lag phases in situations where hazards threaten specimens over several generations. We tested this in three generations of the freshwater crustacean Daphnia lumholtzi using the three-spined stickleback Gasterosteus aculeatus as predator. In the presence of chemical cues from fish D. lumholtzi expresses elongated head and tail spines. In the F0 generation defenses are constraint by a comparatively long lag phase and are not developed prior to the 3rd instar. In the F1, and F2 of induced animals this lag phase is shortened and defenses are developed upon birth. We show that induction of TGP in the mothers takes place already during the juvenile stages and transfers to the offspring generation in forms of shortened time lags and enhanced trait expression. When progeny is additionally exposed to fish cues as embryos, the addition of maternal and embryonic effects further enhances the magnitude of defense expression. Our findings detail a distinguished strategy of transgenerational phenotypic plasticity which allows to shorten lag phases of trait changes in phenotypic plasticity.

中文翻译：

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更高，更快，更好：母体效应缩短了水蚤的后代时间并增加了形态防御能力

猎物物种可以通过诱导形成形态，生活史或行为防御的表型可塑性来对掠食者的存在做出反应。这些所谓的诱导防御在成本效益框架内得到了发展。它们仅在需要时才形成，而在不存在掠食者的情况下可以节省与防御相关的成本。但是，与永久防御相比，劣势是捕食者感知与防御完全形成之间的滞后阶段。当捕食风险持续较长时间（例如，超过一代人并挑战猎物后代）时，这一点尤其重要。我们假设在危害几代人威胁标本的情况下，跨代诱导的表型可塑性减少了滞后阶段。我们在三代淡水甲壳动物水蚤（Daphnia lumholtzi）中测试了这一点，使用三棘刺背G Gasterosteus aculeatus作为捕食者。在鱼类的化学提示存在下，D。lumholtzi表达了细长的头和尾棘。在F0代中，防御受到相对较长的滞后阶段的约束，并且在第三龄之前没有发展。在诱导动物的F1和F2中，这种滞后阶段缩短了，并且在出生时就形成了防御能力。我们表明，母亲中的TGP诱导已经发生在幼年期，并以缩短的时间滞后和增强的性状表达的形式转移至后代。当子代额外暴露于鱼线索作为胚胎时，母体和胚胎效应的添加进一步增强了防御表达的强度。