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.

处于食物链营养级之间的动物，需同时平衡抵御天敌与获取资源的双重生存压力。有毒动物可利用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，动物接触天敌的频率越高，其毒液中防御性组分相较于攻击性组分的占比就会越高；而与猎物的协同进化军备竞赛加剧时，则会出现相反的趋势。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），则可能会减少攻击性毒液组分的合成。在本研究中，我们借助中宇宙实验（mesocosm）调控蝎子对替代脊椎动物天敌以及鲜活、死亡猎物的接触频次，以此探究蝎子毒液组分的变化情况。经过六周实验后，接触过替代天敌的蝎子与未接触过天敌的对照组蝎子相比，其毒液的化学组成存在显著差异。该差异表现为部分对脊椎动物细胞有毒性的化合物占比相对上升，而部分对其无脊椎猎物有效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提供了实证依据。这类毒液组分的改变或可提升包含有毒动物的食物网的稳定性。