Data from: Changes in predator exposure, but not diet induce phenotypic plasticity in scorpion venom

Animals embedded between trophic levels must simultaneously balance pressures to deter predators and acquire resources. Venomous animals may use venom toxins to mediate both pressures, and thus changes in this balance may alter the composition of venoms. Basic theory suggests that greater exposure to a predator should induce a larger proportion of defensive venom components relative to offensive venom components, while increases in arms races with prey will elicit the reverse. Alternatively, reducing the need for venom expenditure for food acquisition, for example because of an increase in scavenging, may reduce the production of offensive venom components. Here, we investigated changes in scorpion venom composition using a mesocosm experiment where we manipulated scorpions' exposure to a surrogate vertebrate predator and live and dead prey. After six weeks, scorpions exposed to surrogate predators exhibited significantly different venom chemistry compared with naive scorpions. This change included a relative increase in some compounds toxic to vertebrate cells and a relative decrease in some compounds effective against their invertebrate prey. Our findings provide, to our knowledge, the first evidence for adaptive plasticity in venom composition. These changes in venom composition may increase the stability of food webs involving venomous animals.

处于食物链营养层级间的动物，需同时权衡两类核心生存压力：抵御天敌捕食与获取食物资源。有毒动物可借助毒液毒素同时调控这两类压力，因此生存平衡的改变可能会影响毒液的组分构成。基础理论表明，当动物更多暴露于天敌威胁时，其毒液中防御性组分的占比应相较于攻击性组分有所提升；而当与猎物的协同进化军备竞赛加剧时，则会呈现相反的变化趋势。此外，若降低获取食物所需的毒液消耗——例如因食腐行为增多而减少主动捕猎——则可能会降低攻击性毒液组分的合成量。本研究通过中宇宙模拟实验（mesocosm experiment），调控蝎子对脊椎动物天敌替代物以及鲜活、腐食猎物的暴露情境，以此探究蝎子毒液组分的动态变化。六周后，暴露于天敌替代物的蝎子，其毒液化学成分与未接触过天敌的空白对照组蝎子存在显著差异。该差异具体体现为：部分对脊椎动物细胞具有毒性的化合物占比相对上升，而部分对其无脊椎猎物具有杀伤效能的化合物占比相对下降。据我们所知，本研究结果首次为毒液组分的适应性可塑性（adaptive plasticity）提供了实证依据。这类毒液组分的变化或可提升包含有毒动物的食物网的整体稳定性。