Pelster Bernd, Giacomin Marina, Wood Chris M, Val Adalberto L
Institute of Zoology, University of Innsbruck, Technikerstr. 25, 6020, Innsbruck, Austria.
Center for Molecular Biosciences, University Innsbruck, Innsbruck, Austria.
J Comp Physiol B. 2016 Jul;186(5):615-24. doi: 10.1007/s00360-016-0981-5. Epub 2016 Apr 5.
The jeju Hoplerythrinus unitaeniatus and the traira Hoplias malabaricus are two closely related erythrinid fish, both possessing a two-chambered physostomous swimbladder. In the jeju the anterior section of the posterior bladder is highly vascularized and the swimbladder is used for aerial respiration; the traira, in turn, is a water-breather that uses the swimbladder as a buoyancy organ and not for aerial oxygen uptake. Observation of the breathing behavior under different levels of water oxygenation revealed that the traira started aquatic surface respiration only under severe hypoxic conditions and did not breathe air. In the jeju air-breathing behavior was observed under normoxic conditions, and the frequency of air-breathing was significantly increased under hypoxic conditions. Unexpectedly, even under hyperoxic conditions (30 mg O2 L(-1)) the jeju continued to take air breaths, and compared with normoxic conditions the frequency was not reduced. Because the frequently air-exposed swimbladder tissue faces higher oxygen partial pressures than normally experienced by other fish tissues, it was hypothesized that in the facultative air-breathing jeju, swimbladder tissue would have a higher antioxidative capacity than the swimbladder tissue of the water breathing traira. Measurement of total glutathione (GSSG/GSH) concentration in anterior and posterior swimbladder tissue revealed a higher concentration of this antioxidant in swimbladder tissue as compared to muscle tissue in the jeju. Furthermore, the GSSG/GSH concentration in jeju tissues was significantly higher than in traira tissues. Similarly, activities of enzymes involved in the breakdown of reactive oxygen species were significantly higher in the jeju swimbladder as compared to the traira swimbladder. The results show that the jeju, using the swimbladder as an additional breathing organ, has an enhanced antioxidative capacity in the swimbladder as compared to the traira, using the swimbladder only as a buoyancy organ.
济州霍氏红肌脂鲤（Hoplerythrinus unitaeniatus）和巴西狗脂鲤（Hoplias malabaricus）是两种亲缘关系密切的红肌脂鲤科鱼类，二者都拥有一个两室的有鳔管的鳔。在济州霍氏红肌脂鲤中，后鳔的前部高度血管化，鳔用于空气呼吸；而巴西狗脂鲤则是通过水呼吸，它将鳔用作浮力器官，而非用于摄取空气中的氧气。对不同水氧合水平下呼吸行为的观察表明，巴西狗脂鲤仅在严重缺氧条件下才开始进行水面呼吸，且不呼吸空气。在济州霍氏红肌脂鲤中，在常氧条件下观察到了空气呼吸行为，而在缺氧条件下空气呼吸频率显著增加。出乎意料的是，即使在高氧条件下（30毫克氧气/升），济州霍氏红肌脂鲤仍继续进行空气呼吸，与常氧条件相比频率并未降低。由于频繁暴露于空气中的鳔组织面临比其他鱼类组织通常所经历的更高的氧分压，因此推测在兼性空气呼吸的济州霍氏红肌脂鲤中，鳔组织的抗氧化能力会高于水呼吸的巴西狗脂鲤的鳔组织。对鳔前后部组织中总谷胱甘肽（GSSG/GSH）浓度的测量显示，与济州霍氏红肌脂鲤的肌肉组织相比，鳔组织中这种抗氧化剂的浓度更高。此外，济州霍氏红肌脂鲤组织中的GSSG/GSH浓度显著高于巴西狗脂鲤组织。同样，与巴西狗脂鲤的鳔相比，济州霍氏红肌脂鲤的鳔中参与活性氧分解的酶的活性显著更高。结果表明，与仅将鳔用作浮力器官的巴西狗脂鲤相比，将鳔用作额外呼吸器官的济州霍氏红肌脂鲤的鳔具有增强的抗氧化能力。
