Data from: Seasonal changes in diet and toxicity in the Climbing Mantella frog (Mantella laevigata)

Poison frogs acquire chemical defenses from the environment for protection against potential predators. These defensive chemicals are lipophilic alkaloid toxins that are sequestered by poison frogs from dietary arthropods and stored in skin glands. Despite decades of research focusing on identifying poison frog toxins, we know relatively little about how environmental variation and subsequent arthropod availability impacts toxicity in poison frogs. We investigated how seasonal environmental variation influences poison frog toxin profiles through changes in the diet of the Climbing Mantella (Mantella laevigata). We collected M. laevigata females on the Nosy Mangabe island reserve in Madagascar during the wet and dry seasons and tested the hypothesis that seasonal differences in temperature and rainfall are associated with changes in the diet and skin toxin profiles of M. laevigata. The arthropod diet of each frog was characterized into five groups (i.e. ants, termites, mites, larvae and other) using visual identification and cytochrome oxidase 1 DNA barcoding. We found that frog diet differed between the wet and dry seasons, where frogs had a more diverse diet in the wet season and consumed a higher percentage of ants in the dry season. To determine if these differences in diet were associated with variation in frog defensive chemical composition, we used gas chromatography / mass spectrometry to quantify toxins from individual skin samples. Although the assortment of identified toxins was similar across seasons, we detected significant differences in the abundance of certain alkaloids, which we hypothesize reflects seasonal variation in the diet of M. laevigata. We suggest that tThese variations could originate from seasonal changes in either arthropod leaf litter composition or changes in frog behavioral patterns between wet and dry seasons. Although additional studies are needed to understand the consequences of long-term environmental shifts, this work suggests that toxin profiles are relatively robust against short-term environmental perturbations.

箭毒蛙（poison frog）从环境中获取化学防御物质以抵御潜在捕食者。这类防御性化学物质为亲脂性生物碱毒素（lipophilic alkaloid toxins），由箭毒蛙从其摄食的节肢动物（arthropods）中富集，并储存在皮肤腺体中。尽管数十年来的研究多聚焦于箭毒蛙毒素的鉴定，但我们对环境变化以及随之变化的节肢动物可获得性如何影响箭毒蛙的毒性水平仍知之甚少。
本研究以攀岩曼蛙（Mantella laevigata）为对象，探究了季节性环境变化如何通过其饮食变化影响箭毒蛙的毒素谱。我们在马达加斯加的诺西芒加贝岛保护区内，于湿季和旱季分别采集了攀岩曼蛙的雌性个体，并验证了如下假说：温湿度的季节差异与攀岩曼蛙的饮食及皮肤毒素谱的变化存在关联。
研究人员通过形态学鉴定与细胞色素氧化酶1（cytochrome oxidase 1）DNA条形码技术，将每只攀岩曼蛙的节肢动物饮食划分为五大类：蚂蚁、白蚁、螨类、幼虫及其他类群。研究结果显示，蛙类的饮食在湿季与旱季存在显著差异：湿季的饮食多样性更高，而旱季的蚂蚁摄入占比更高。
为明确此类饮食差异是否与蛙类防御性化学成分的变化相关，我们采用气相色谱-质谱联用法（gas chromatography / mass spectrometry）对单只皮肤样本中的毒素进行了定量分析。尽管各季节中鉴定出的毒素种类组成相似，但我们检测到部分生物碱的含量存在显著差异，我们推测这一现象反映了攀岩曼蛙饮食的季节性变化。
我们认为，此类变化可能源于两个方面：一是节肢动物在枯落物中的组成随季节发生改变，二是蛙类在湿季与旱季的行为模式存在差异。尽管仍需开展更多研究以明确长期环境变化带来的影响，但本研究结果表明，毒素谱对短期环境扰动具有相对较强的耐受性。