Paramos are high-elevation tropical Andean ecosystems above the tree line that display variable temperature and frequent freezing spells. Because a significant anuran community lives in this environment, physiological protection against freezing must characterise individuals in this community. Antifreeze protection has been studied in amphibians from other communities, and it is likely that Paramo anurans rely on the same underlying molecules that convey such protection to Nearctic species. However, given the pervasive presence of freezing spells in the Paramos year-round, the processes of activating protection mechanisms may differ from that of seasonal counterparts. Accordingly, this study investigated cryoprotection strategies in high-elevation tropical frogs, using as a model the terrestrial and nocturnal genus Pristimantis, specifically P. bogotensis, P. elegans and P. nervicus from Paramos, and the warm ecosystem counterparts P. insignitus, P. megalops and P. sanctaemartae. We focused on freeze tolerance and its relationship with glucose accumulation and ice formation. Under field conditions, the highest elevation P. nervicus exhibited higher glucose concentration at dawn compared to noon (1.7 ± 0.6 mmol/L versus 3.5 ± 1.32 mmol/L). Under experimental thermal freeze exposure for 2 hours between −2 and −4 ºC, the glucose concentration of the three Paramo species increased but physiological diversity was evident (P. nervicus 126%; P. bogotensis 100%; and P. elegans 55%). During this test, body ice formation was assessed calorimetrically. The species with the highest body ice formation was P. bogotensis (17% ± 5.37; maximum value: 63%; n = 8), followed by P. nervicus (5% ± 3.27; maximum value: 11%; n = 5) and P. elegans (0.34% ± 0.09; maximum value: 1%; n = 4). The study shows physiological diversity both within a genus and across the amphibian community around the freezing contour. Overall, Paramo species differ in freezing physiology from their low-elevation counterparts. Thus, climate shifts increasing freezing spells may affect the structure of communities in this zone.

中文翻译：

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新热带青蛙的耐冻性：使用高海拔和中等海拔 Pristimantis 物种的属内比较

帕拉莫斯是树线以上的高海拔热带安第斯生态系统，显示出温度变化和频繁的冰冻期。因为在这种环境中生活着一个重要的无尾猿群落，所以对冰冻的生理保护必须是这个群落中个体的特征。已经在来自其他群落的两栖动物中研究了防冻保护，并且 Paramo anurans 很可能依赖于将这种保护传递给 Nearctic 物种的相同底层分子。然而，鉴于帕拉莫斯全年普遍存在冰冻法术，激活保护机制的过程可能与季节性对应的过程不同。因此，本研究调查了高海拔热带青蛙的冷冻保护策略，以陆地和夜间活动的属为模型。普里斯蒂曼蒂斯， 具体来说P. bogotensis,线虫和P. nervicus来自 Paramos 和温暖的生态系统同行P. insignitus,P. megalops和P. sanctaemartae. 我们专注于耐冻性及其与葡萄糖积累和结冰的关系。在野外条件下，最高海拔P. nervicus与中午相比，黎明时葡萄糖浓度更高（1.7 ± 0.6 mmol/L 对 3.5 ± 1.32 mmol/L）。在 -2 和 -4 ºC 之间 2 小时的实验性热冷冻暴露下，三种 Paramo 物种的葡萄糖浓度增加，但生理多样性明显（P. nervicus126%；P. bogotensis100%；和线虫55%）。在该测试期间，通过量热法评估身体冰的形成。体冰形成最多的物种是P. bogotensis（17% ± 5.37；最大值：63%；n = 8），然后是P. nervicus（5% ± 3.27；最大值：11%；n = 5）和线虫（0.34% ± 0.09；最大值：1%；n = 4）。该研究显示了一个属内和整个冰冻轮廓周围两栖动物群落的生理多样性。总体而言，Paramo 物种的冷冻生理学与低海拔物种不同。因此，气候变化增加冰冻期可能会影响该地区社区的结构。