背景:蛇毒可以表现出显著的种间和种内变异。虽然不同的生态和环境因素在理论上解释了这种变化,只有少数研究试图揭示它们的确切作用。这种知识差距不仅阻碍了我们对毒液进化的理解,而且可能对蛇咬伤治疗产生可怕的后果。为了解决这个缺点,我们调查了罗素毒蛇(Daboiarusselii)和眼镜眼镜蛇(Najanaja)毒液的进化生态学,印度的两条临床上最重要的蛇造成了惊人数量的人类死亡和残疾。
方法:几个属于多个离合器(n=9)的D.russelii和N.naja的个体(n=226)及其母亲被囚禁以获取个体发育阶段特异性毒液。使用各种体外和体内试验,我们评估了猎物的重要性,驱动毒液成分中的个体发育和性别,函数,和效力。
结果:在D.russelii中观察到毒液谱中相当大的个体发育变化,新生儿的毒液对哺乳动物(2.3-2.5×)和爬行动物(2-10×)猎物的效力是青少年和成年人的许多倍。这是关于毒蛇个体发育转变的第一份文献。与之形成鲜明对比的是,N.naja,具有类似于D.Russelii的生物地理分布,在整个开发过程中部署相同的生化鸡尾酒。此外,眼镜蛇毒毒素与各种猎物和捕食者合成靶受体的结合动力学为进化军备竞赛提供了启示。
结论:我们的发现,因此,提供有关生态和生活史特征在塑造蛇毒中的作用的迷人见解。
BACKGROUND: Snake venoms can exhibit remarkable inter- and intraspecific variation. While diverse ecological and environmental factors are theorised to explain this variation, only a handful of studies have attempted to unravel their precise roles. This knowledge gap not only impedes our understanding of venom evolution but may also have dire consequences on snakebite treatment. To address this shortcoming, we investigated the evolutionary ecology of venoms of Russell\'s viper (Daboia russelii) and spectacled cobra (Naja naja), India\'s two clinically most important snakes responsible for an alarming number of human deaths and disabilities.
METHODS: Several individuals (n = 226) of D. russelii and N. naja belonging to multiple clutches (n = 9) and their mothers were maintained in captivity to source ontogenetic stage-specific venoms. Using various in vitro and in vivo assays, we assessed the significance of prey, ontogeny and sex in driving venom composition, function, and potency.
RESULTS: Considerable ontogenetic shifts in venom profiles were observed in D. russelii, with the venoms of newborns being many times as potent as juveniles and adults against mammalian (2.3-2.5 ×) and reptilian (2-10 ×) prey. This is the first documentation of the ontogenetic shift in viperine snakes. In stark contrast, N. naja, which shares a biogeographic distribution similar to D. russelii, deployed identical biochemical cocktails across development. Furthermore, the binding kinetics of cobra venom toxins against synthetic target receptors from various prey and predators shed light on the evolutionary arms race.
CONCLUSIONS: Our findings, therefore, provide fascinating insights into the roles of ecology and life history traits in shaping snake venoms.