Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
Proc Biol Sci. 2019 Jul 24;286(1907):20190832. doi: 10.1098/rspb.2019.0832. Epub 2019 Jul 17.
Our goal was to use novel fibreoptic sensors to make the first direct PCO measurements in the digestive tracts of live freshwater fish (anaesthetized, artificially ventilated, 12°C). PCO levels in gastrointestinal fluids were substantially higher than in blood, and were elevated after feeding. In the carnivorous, gastric rainbow trout, the mean PCO in various parts of the tract increased from 7-13 torr (1 torr = 0.1333 kPa) during fasting to 20-41 torr after feeding, relative to arterial levels of 3.5-4 torr. In the agastric, omnivorous goldfish, the mean gut levels varied from 10-13 torr in fasted animals to 14-18 torr in fed animals, relative to arterial levels of 5-7 torr. These elevated PCO values were associated with surprisingly high [Formula: see text] concentrations (greater than 40 mmol l) in the intestinal chyme. Incubations of food pellets with acid or water revealed endogenous PCO generation sufficient to explain gastric PCO in fed trout and anterior intestine PCO in fed goldfish. The impacts of possible equilibration with venous blood draining the tract are assessed. We conclude that fish are already coping with PCO levels in the internal gastrointestinal environment many-fold greater than those of current concern in the external environment for climate change and aquacultural scenarios.
我们的目标是使用新型光纤传感器首次在活体淡水鱼（麻醉、人工通气、12°C）的消化道内进行直接 PCO 测量。胃肠液中的 PCO 水平明显高于血液，进食后会升高。在肉食性的胃彩虹鳟鱼中，与动脉水平 3.5-4 托相比，空腹时消化道各部位的平均 PCO 从 7-13 托（1 托=0.1333kPa）增加到进食后的 20-41 托。在非胃、杂食性金鱼中，空腹动物的平均肠道水平从 10-13 托变化到进食动物的 14-18 托，与动脉水平 5-7 托相比。这些升高的 PCO 值与肠道食糜中惊人的高[公式：见文本]浓度（大于 40mmol/L）有关。用酸或水孵育食物颗粒表明，内源性 PCO 生成足以解释喂食鳜鱼的胃 PCO 和喂食金鱼的前肠 PCO。评估与流经消化道的静脉血可能达到平衡的影响。我们得出结论，鱼类已经在应对内部胃肠道环境中的 PCO 水平，这些水平比当前气候变化和水产养殖情景中外部环境中令人关注的水平高出许多倍。
