Dietary sequestration of defensive steroids in nuchal glands of the Asian snake Rhabdophis tigrinus
Dietary sequestration of defensive steroids in nuchal glands of the Asian snake Rhabdophis tigrinus
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DOI：
10.1073/pnas.0610785104
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发表时间：
2007-02-13
影响因子：
11.1
通讯作者：
Schroeder, Frank C.
中科院分区：
文献类型：
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作者：
Hutchinson, Deborah A.;Mori, Akira;Schroeder, Frank C.
亚洲蛇横纹蛇的脖子上有专门的防御腺体，其中含有被称为蟾二烯内酯的类固醇毒素。我们假设r.t tigrinus不合成这些防御性类固醇，而是将其作为猎物吃掉的蟾蜍的毒素隔离开来。为了验证这一假设，我们对在无蟾蜍和有蟾蜍的地方收集的蛇的腺液进行了化学分析。我们还进行了饲养实验，将幼鼠饲养在控制饲料中，包括或不包括蟾蜍。我们证明了老虎颈腺中的强心性类固醇是从食性蟾蜍中获得的。我们进一步表明，含有高水平蟾二烯内酯的母亲可以为其后代提供毒素。只有喂食蟾蜍或出生在含有高浓度这种化合物的环境中，幼仔的颈腺才会含有蟾二烯内酯。由于有毒猎物的地理分布反映在腺液的化学成分中，因此没有蟾蜍的地区的蛇没有类固醇毒素的保护。我们的研究结果证实，饮食毒素的隔离是该物种反掠食性行为的地理差异的基础，并提供了在特定脊椎动物结构中隔离防御化合物的独特例子。
The Asian snake Rhabdophis tigrinus possesses specialized defensive glands on its neck that contain steroidal toxins known as bufadienolides. We hypothesized that R. tigrinus does not synthesize these defensive steroids but instead sequesters the toxins from toads it consumes as prey. To test this hypothesis, we conducted chemical analyses on the glandular fluid from snakes collected in toad-free and toad-present localities. We also performed feeding experiments in which hatchling R. tigrinus were reared on controlled diets that either included or lacked toads. We demonstrate that the cardiotonic steroids in the nuchal glands of R. tigrinus are obtained from dietary toads. We further show that mothers containing high levels of bufadienolides can provision their offspring with toxins. Hatchlings had bufadienolides in their nuchal glands only if they were fed toads or were born to a dam with high concentrations of these compounds. Because geographic patterns in the availability of toxic prey are reflected in the chemical composition of the glandular fluid, snakes in toad-free regions are left undefended by steroidal toxins. Our findings confirm that the sequestration of dietary toxins underlies geographic variation in antipredatory behavior in this species and provide a unique example of sequestered defensive compounds in a specialized vertebrate structure.