Predators usurp prey defenses? Toxicokinetics of tetrodotoxin in common garter snakes after consumption of rough-skinned newts
Predators usurp prey defenses? Toxicokinetics of tetrodotoxin in common garter snakes after consumption of rough-skinned newts
复制标题
掠食者篡夺了猎物的防御？
作者：
B. L. Williams;C. Hanifin;E. D. Brodie;E. D. Brodie
蛇是两栖动物等生物体的常见捕食者，具有对其他捕食者致命的毒性防御。因为蛇没有将猎物解剖成可食用或不可食用的成分的选择，它们在试图捕食时面临着全剂量的任何化学防御。这种限制可能导致了激烈的选择有利于替代机制的演变，处理猎物毒素。这些机制可以是生理性的（例如，对猎物毒素的抗性）或行为（例如，毒素取样和剔除）。当生理抗性出现时，就可能导致毒素的生物积累。我们研究了普通束带蛇（Thamnophis sirtalis）和粗皮蝾螈（Taricha granulosa）之间的共同进化相互作用，粗皮蝾螈含有一种强大的神经毒素，称为河豚毒素（TTX）。在某些与蝾螈共生的种群中，T. Sirtalis已经进化出对TTX的抗性。我们研究了TTX在T. Sirtalis在口服剂量的TTX后，研究蛇隔离TTX的可能性。TTX在蛇肝中的半衰期估计为8.1天。因此，TTX单次给药99%的清除率平均为61天。在蝾螈消费期间和之后的中毒的负面健身后果可以通过选择蝾螈的化学防御来保护蛇自己的捕食者来平衡。蛇和蝾螈之间的共同进化动态的会计必须纳入消费后的影响挥之不去的TTX。
Snakes are common predators of organisms, such as amphibians, with toxic defenses that can be lethal to other predators. Because snakes do not have the option of dissecting prey into edible versus inedible components, they face a full dose of any chemical defenses encountered during attempted predation. This limitation has likely resulted in intense selection favoring the evolution of alternative mechanisms for dealing with prey toxins. These mechanisms can be physiological (e.g., resistance to prey toxins) or behavioral (e.g., toxin sampling and rejection). When physiological resistance arises, the possibility of bioaccumulation of a toxin results. We examined the coevolutionary interaction between the common garter snake (Thamnophis sirtalis) and the rough-skinned newt (Taricha granulosa), which contains a powerful neurotoxin called tetrodotoxin (TTX). In some populations syntopic with newts, individuals of T. sirtalis have evolved resistance to TTX. We examined the persistence of TTX in T. sirtalis after administration of an oral dose of TTX to investigate the possibility that snakes are sequestering TTX. The half-life of TTX in snake liver was estimated at 8.1 days. Accordingly, clearance of 99% of a single dose of TTX averages 61 days. Negative fitness consequences of intoxication during and after newt consumption may be balanced by co-opting the newts’ chemical defense for protection from the snakes’ own predators. Accounting of the coevolutionary dynamic between snakes and newts must incorporate post-consumption affects of lingering TTX.