Insect eggs exert rapid control over an oxygen-water tradeoff
Insect eggs exert rapid control over an oxygen-water tradeoff
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DOI：
10.1098/rspb.2005.3374
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发表时间：
2006-04-07
影响因子：
4.7
通讯作者：
Woods, HA
中科院分区：
文献类型：
--
作者：
Zrubek, B;Woods, HA
在陆地环境中，呼吸气体的交换需要水的代价：获得氧气或二氧化碳需要失去水。昆虫卵应该对这种权衡特别敏感，因为它们不能觅食水，有很高的表面积与体积比，并且经历了大的温度驱动的氧气需求变化。我们实验室以前对一种常见的天蛾（Manduca sexta）卵的研究表明，在发育过程中，代谢率和失水率平行上升。这些相关数据表明，蛋壳电导增加，以适应不断增加的代谢需求。在这里，我们通过实验测试了这个想法，将M。Sexta至15、21（常氧）和35%氧气24小时，同时测量代谢率（如二氧化碳排放）和水分损失。缺氧降低了鸡蛋的代谢率，但导致了水分流失的显著迅速增加。相比之下，高氧对代谢或水分流失没有显着影响。这些数据表明，昆虫卵积极参与平衡氧增益和水分损失，并且它们使用组织氧状态或其一些相关性作为增加蛋壳电导的线索。对电导的快速控制可以使蛋在低代谢需求的初始阶段保存水，从而将呼吸气体交换的水成本推迟到发育后期。
In terrestrial environments, the exchange of respiratory gases exacts a water cost: obtaining oxygen or carbon dioxide requires losing water. Insect eggs should be especially sensitive to this tradeoff-because they are unable to forage for water, have high surface area-to-volume ratios, and experience large temperature-driven changes in oxygen demand. Previous work from our laboratory, on eggs of a common hawkmoth, Manduca sexta, has shown that, during development, metabolic rate and water loss rates rise in parallel. These correlative data suggest that eggshell conductance increases to accommodate increasing metabolic demand. Here, we test this idea experimentally by subjecting eggs of M. sexta to 15, 21 (normoxia) and 35% oxygen for 24 h, while measuring rates of metabolism (as carbon dioxide emission) and water loss. Hypoxia depressed egg metabolic rates, but led to pronounced, rapid increases in water loss. By contrast, hyperoxia had no significant effect on metabolism or water loss. These data demonstrate that insect eggs actively participate in balancing oxygen gain and water loss, and that they use tissue oxygen status, or some correlate of it, as a cue for increasing eggshell conductance. Rapid control over conductance may allow eggs to conserve water during an initial period of low metabolic demand, thereby deferring water costs of respiratory gas exchange until late in development.