Anurans secrete a wide diversity of toxins from skin glands to defend themselves against predators and pathogens. Bufonids produce potent poison in parotoid macroglands located in the postorbital region. Parotoid secretion is a rich source of bioactive compounds with cardiotoxic, cytotoxic and hemolytic activity. Poison content and toxicity may vary between species, populations, and among conspecifics inhabiting the same area. In the present paper, we pre-analyzed the individual variation in cardiotoxicity of parotoid extract of common toads (Bufo bufo Linnaeus, 1758) and impact of body mass (BM), snout to vent length (SVL), and body condition (BC) of toad on the poison toxicity. We hypothesized that large toads produce poison with higher cardiotoxicity than smaller ones. Parotoid extract was fractionated by reverse phase chromatography, and then in vitro physiological bioassays were carried out on the semi-isolated hearts of the mealworm beetle (Tenebrio molitor Linnaeus, 1758) to determine cardiotoxicity of the whole poison and separated fractions. Generalized linear mixed models were used to determine effects of BM, SVL, and BC on the poison toxicity. We recorded significant changes in the insect heart contractility after treatment with the whole poison and separated fractions. We found an individual variation in cardiotoxicity of the parotoid extract which was explained by the body size of toad. Poison of smaller toads displayed a negative, whereas poison of larger toads positive, chronotropic effect on the heart contractility. Thus, we conclude that the effectiveness of parotoid secretion in repelling predators may vary depending on the toad individual size.

中文翻译：

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普通蟾蜍腮腺分泌物心脏毒性的个体差异取决于体型——初步结果

无尾猿从皮肤腺分泌多种毒素，以保护自己免受捕食者和病原体的侵害。Bufonids 在位于眶后区域的腮腺大腺中产生强效毒药。腮腺分泌物是具有心脏毒性、细胞毒性和溶血活性的生物活性化合物的丰富来源。毒物含量和毒性可能因物种、种群和居住在同一地区的同种物种而异。在本论文中，我们预先分析了普通蟾蜍 (Bufo bufo Linnaeus, 1758) 的心脏毒性的个体差异以及体重 (BM)、口鼻至排气口长度 (SVL) 和身体状况 (BC) 的影响蟾蜍对毒的毒性。我们假设大型蟾蜍比较小的蟾蜍产生具有更高心脏毒性的毒物。腮腺提取物通过反相色谱分离，然后对黄粉虫甲虫 (Tenebrio molitor Linnaeus, 1758) 的半离体心脏进行体外生理生物测定，以确定整个毒物和分离部分的心脏毒性。广义线性混合模型用于确定 BM、SVL 和 BC 对毒物毒性的影响。我们记录了在用整个毒物和分离的部分处理后昆虫心脏收缩力的显着变化。我们发现腮腺提取物的心脏毒性存在个体差异，这可以用蟾蜍的体型来解释。小蟾蜍的毒药对心脏收缩力有负面影响，而大蟾蜍的毒药对心脏收缩力有积极的变时作用。因此，我们得出结论，腮腺分泌物在排斥捕食者方面的有效性可能因蟾蜍个体大小而异。