Termite soldiers constitute the defensive frontline of the colonies, despite workers also perform such tasks, especially within the Neotropical Apicotermitinae, in which all species are soldierless. Workers of the genus Ruptitermes display an extreme form of defense, characterized by body rupture and release of a sticky secretion. Previous observations suggested that such behavior may be advantageous against enemies, but the chemical composition of this secretion has been neglected. Here we firstly provide the proteomic profile of the defensive secretion of Ruptitermes reconditus and Ruptitermes pitan workers. Additionally, the mechanisms of action of this behavior was evaluated through different bioassays. A total of 446 proteins were identified in R. reconditus and 391 proteins in R. pitan, which were classified into: toxins, defensins and proteolytic enzymes; sticky components/ alarm communication; proteins related to detoxification processes; proteins involved in folding/conformation and post-translational modifications; housekeeping proteins; and uncharacterized/hypothetical proteins. According to the bioassays, the self-sacrifice is triggered by a physical stimulus, and the defensive secretion may cause immobility and death of the opponents. Assuming that termites are abundant in the tropics and therefore exposed to predators, suicidal behaviors seem to be advantageous, since the loss of an individual benefit the whole colony. SIGNIFICANCE: Although recent studies have reported the biochemical composition of different weapons in soldiered species of termites, such efforts had not been applied to sordierless taxa up until now. Thus, this is the first report of the defensive mechanisms in soldierless termite species based on proteomic analysis. The diversity of compounds, which included toxin-like and mucin-like proteins, reflect the mechanisms of action of the defensive secretion released by termite workers, which may cause immobility and death of the opponents. Our findings may contribute to the knowledge regarding the development of defensive strategies in termites, especially in groups which lost the soldier caste during the evolution.

中文翻译：

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蛋白质组学成分提供了对无兵属 Ruptitermes 白蚁工蚁防御性分泌的深入了解。

白蚁士兵构成了殖民地的防御前线，尽管工人也执行此类任务，特别是在所有物种都没有士兵的新热带Apicotermitinae内。Ruptitermes 属的工人表现出一种极端的防御形式，其特征是身体破裂并释放出粘性分泌物。先前的观察表明，这种行为可能对敌人有利，但这种分泌物的化学成分被忽略了。在这里，我们首先提供了 Ruptitermes reconditus 和 Ruptitermes pitan 工人的防御性分泌的蛋白质组学特征。此外，通过不同的生物测定评估了这种行为的作用机制。R. reconditus 共鉴定出 446 种蛋白质，R. pitan 共鉴定出 391 种蛋白质，分为：毒素、防御素和蛋白水解酶；粘性元件/报警通讯；与解毒过程相关的蛋白质；参与折叠/构象和翻译后修饰的蛋白质；管家蛋白质；和未表征/假设的蛋白质。根据生物测定，自我牺牲是由物理刺激触发的，防御性分泌物可能导致对手无法动弹和死亡。假设白蚁在热带地区很丰富，因此暴露在捕食者面前，自杀行为似乎是有利的，因为失去一个个体会使整个蚁群受益。意义：尽管最近的研究报告了不同武器在士兵白蚁中的生化成分，但直到现在，这种努力还没有应用于无白蚁类群。因此，这是基于蛋白质组学分析的无兵白蚁物种防御机制的第一份报告。化合物的多样性，包括毒素样蛋白和粘蛋白样蛋白，反映了白蚁工蚁释放的防御性分泌物的作用机制，这可能导致对手的不动和死亡。我们的研究结果可能有助于了解白蚁防御策略的发展，特别是在进化过程中失去士兵种姓的群体中。