Department of Biology and Centre for Forest Inter-Disciplinary Research (C-FIR), University of Winnipeg, Winnipeg MB R3B2E9, Canada.
Integr Comp Biol. 2011 Sep;51(3):364-73. doi: 10.1093/icb/icr076. Epub 2011 Jul 8.
White-nose syndrome (WNS) has caused alarming declines of North American bat populations in the 5 years since its discovery. Affected bats appear to starve during hibernation, possibly because of disruption of normal cycles of torpor and arousal. The importance of hydration state and evaporative water loss (EWL) for influencing the duration of torpor bouts in hibernating mammals recently led to "the dehydration hypothesis," that cutaneous infection of the wing membranes of bats with the fungus Geomyces destructans causes dehydration which in turn, increases arousal frequency during hibernation. This hypothesis predicts that uninfected individuals of species most susceptible to WNS, like little brown bats (Myotis lucifugus), exhibit high rates of EWL compared to less susceptible species. We tested the feasibility of this prediction using data from the literature and new data quantifying EWL in Natterer's bats (Myotis nattereri), a species that is, like other European bats, sympatric with G. destructans but does not appear to suffer significant mortality from WNS. We found that little brown bats exhibited significantly higher rates of normothermic EWL than did other bat species for which comparable EWL data are available. We also found that Natterer's bats exhibited significantly lower rates of EWL, in both wet and dry air, compared with values predicted for little brown bats exposed to identical relative humidity (RH). We used a population model to show that the increase in EWL required to cause the pattern of mortality observed for WNS-affected little brown bats was small, equivalent to a solitary bat hibernating exposed to RH of ∼95%, or clusters hibernating in ∼87% RH, as opposed to typical near-saturation conditions. Both of these results suggest the dehydration hypothesis is plausible and worth pursuing as a possible explanation for mortality of bats from WNS.
自发现以来的 5 年内，白鼻综合征（WNS）已导致北美的蝙蝠数量急剧下降。受感染的蝙蝠在冬眠期间似乎会饿死，这可能是由于正常的休眠和苏醒周期被打乱。水合状态和蒸发失水（EWL）对影响冬眠哺乳动物休眠时间的重要性最近导致了“脱水假说”，即真菌 Geomyces destructans 对蝙蝠翅膀膜的皮肤感染导致脱水，从而增加了冬眠期间的苏醒频率。该假说预测，最易感染 WNS 的物种（如小棕蝠（Myotis lucifugus））的未感染个体与较不易感染的物种相比，表现出较高的 EWL 率。我们使用文献中的数据和新数据来检验这一预测的可行性，这些数据量化了 Natterer 蝙蝠（Myotis nattereri）的 EWL，该物种与其他欧洲蝙蝠一样，与 G. destructans 共存，但似乎不会因 WNS 而遭受重大死亡率。我们发现，小棕蝠在正常体温下的 EWL 率明显高于其他具有可比 EWL 数据的蝙蝠物种。我们还发现，与暴露在相同相对湿度（RH）下的小棕蝠相比，Natterer 蝙蝠在潮湿和干燥空气中的 EWL 率明显较低。我们使用种群模型表明，导致受影响的小棕蝠观察到的死亡率模式所需的 EWL 增加量很小，相当于单独一只蝙蝠在 RH 约为 95%的情况下休眠，或者集群在 RH 约为 87%的情况下休眠，而不是典型的接近饱和的情况。这两个结果都表明，脱水假说似乎是合理的，值得作为 WNS 导致蝙蝠死亡的可能解释进行研究。
