Biological Sciences, Zoophysiology Section, Aarhus University, Denmark.
Comp Biochem Physiol A Mol Integr Physiol. 2011 Feb;158(2):207-14. doi: 10.1016/j.cbpa.2010.10.029. Epub 2010 Nov 3.
Air-breathing fish are common in the tropics, and their importance in Asian aquaculture is increasing, but the respiratory physiology of some of the key species such as the striped catfish, Pangasianodon hypophthalmus Sauvage 1878 is unstudied. P. hypophthalmus is an interesting species as it appears to possess both well-developed gills and a modified swim bladder that functions as an air-breathing organ indicating a high capacity for both aquatic and aerial respiration. Using newly developed bimodal intermittent-closed respirometry, the partitioning of oxygen consumption in normoxia and hypoxia was investigated in P. hypophthalmus. In addition the capacity for aquatic breathing was studied through measurements of oxygen consumption when access to air was denied, both in normoxia and hypoxia, and the critical oxygen tension, Pcrit, was also determined during these experiments. Finally, gill ventilation and air-breathing frequency were measured in a separate experiment with pressure measurements from the buccal cavity. The data showed that P. hypophthalmus is able to maintain standard metabolic rate (SMR) through aquatic breathing alone in normoxia, but that air-breathing is important during hypoxia. Gill ventilation was reduced during air-breathing, which occurred at oxygen levels below 8 kPa, coinciding with the measured Pcrit of 7.7 kPa. The findings in this study indicate that the introduction of aeration into the aquaculture of P. hypophthalmus could potentially reduce the need to air-breathe. The possibility of reducing air-breathing frequency may be energetically beneficial for the fish, leaving more of the aerobic scope for growth and other activities, due to the proposed energetic costs of surfacing behavior.
呼吸空气的鱼类在热带地区很常见，它们在亚洲水产养殖中的重要性日益增加，但一些关键物种的呼吸生理特性，如条纹𬶐，Pangasianodon hypophthalmus Sauvage 1878，尚未得到研究。P. hypophthalmus 是一个有趣的物种，因为它似乎同时拥有发育良好的鳃和改良的鳔，后者作为呼吸器官具有空气呼吸功能，表明它具有很强的水生和空气呼吸能力。使用新开发的双模间歇闭路呼吸测量法，研究了 P. hypophthalmus 在常氧和低氧条件下耗氧量的分配。此外，还通过在常氧和低氧条件下测量禁止接触空气时的耗氧量来研究其水生呼吸能力，并在这些实验中确定临界氧张力 Pcrit。最后，在单独的实验中通过测量口腔腔压来测量鳃通气和空气呼吸频率。数据表明，P. hypophthalmus 在常氧条件下仅通过水生呼吸就能维持标准代谢率（SMR），但在低氧条件下空气呼吸很重要。空气呼吸时，鳃通气减少，发生在氧气水平低于 8 kPa 时，与测量的 Pcrit 7.7 kPa 相吻合。本研究的结果表明，在 P. hypophthalmus 的水产养殖中引入充气可能会减少其对空气呼吸的需求。减少空气呼吸频率的可能性可能对鱼类有利，因为浮出水面行为的拟议能量成本，为生长和其他活动留下更多的有氧空间。
