蟑螂和一些昆虫会周期性地停止呼吸，这让科学家们百思不得其解。一种假设认为，通过关闭外骨骼上名为通气孔的一个微小的呼吸瓣，这些昆虫能够防止体内的蒸发作用。

据美国《科学》杂志在线新闻报道，研究人员最近对这一假设进行了测试。他们在5周的时间里，将一种宠物蟑螂（Nauphoeta cinerea，如上图）放置在具有不同湿度的瓶子中。与在闷热的环境中相比，在干燥瓶子中的蟑螂打开通气孔的时间要比前者大约少40%。研究人员在9月份出版的《实验生物学杂志》上报告了这一发现。很显然，这些昆虫似乎能够通过屏住呼吸来保持体内的水分。

Journal of Experimental Biology 212, 2773-2780 (2009)doi: 10.1242/jeb.031310

Cockroaches breathe discontinuously to reduce respiratory water loss

Natalie G. Schimpf*, Philip G. D. Matthews, Robbie S. Wilson and Craig R. White

School of Biological Sciences, Faculty of Biological and Chemical Sciences, University of Queensland, Brisbane 4000, Australia

The reasons why many insects breathe discontinuously at rest are poorly understood and hotly debated. Three adaptive hypotheses attempt to explain the significance of these discontinuous gas exchange cycles (DGCs), whether it be to save water, to facilitate gas exchange in underground environments or to limit oxidative damage. Comparative studies favour the water saving hypothesis and mechanistic studies are equivocal but no study has examined the acclimation responses of adult insects chronically exposed to a range of respiratory environments. The present research is the first manipulative study of such chronic exposure to take a strong-inference approach to evaluating the competing hypotheses according to the explicit predictions stemming from them. Adult cockroaches (Nauphoeta cinerea) were chronically exposed to various treatments of different respiratory gas compositions (O2, CO2 and humidity) and the DGC responses were interpreted in light of the a priori predictions stemming from the competing hypotheses. Rates of mass loss during respirometry were also measured for animals acclimated to a range of humidity conditions. The results refute the hypotheses of oxidative damage and underground gas exchange, and provide evidence supporting the hypothesis that DGCs serve to reduce respiratory water loss: cockroaches exposed to low humidity conditions exchange respiratory gases for shorter durations during each DGC and showed lower rates of body mass loss during respirometry than cockroaches exposed to high humidity conditions.