OXYGEN-TRANSPORT AND CARDIOVASCULAR-RESPONSES IN SKIPJACK TUNA (KATSUWONUS-PELAMIS) AND YELLOWFIN TUNA (THUNNUS-ALBACARES) EXPOSED TO ACUTE-HYPOXIA
OXYGEN-TRANSPORT AND CARDIOVASCULAR-RESPONSES IN SKIPJACK TUNA (KATSUWONUS-PELAMIS) AND YELLOWFIN TUNA (THUNNUS-ALBACARES) EXPOSED TO ACUTE-HYPOXIA
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DOI：
10.1007/bf00398338
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发表时间：
1992-03-01
期刊：
影响因子：
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通讯作者：
BRILL, RW
中科院分区：
文献类型：
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作者：
BUSHNELL, PG;BRILL, RW
本研究测定了鲣鱼（Katsuwonus pelamis）和黄鳍金枪鱼（Thunnus albacures）（几乎等于1-3公斤体重）对急性缺氧的反应。通过脊髓注射利多卡因防止鱼进行游泳运动，并将其放置在海水输送管的前面以提供鳃的冲压通风。鱼可以通过调整嘴巴的张开来设定自己的通气量。在常氧（吸入水（PO 2> 150 mmHg））和三个缺氧水平（吸入水PO 2几乎等于130、90和50 mmHg）期间连续监测心率、背腹主动脉血压和心输出量。采集水和血液样本，用于测量鳃传入和传出液体中的氧含量。根据这些数据，计算了氧转移的有效性以及鳃和全身血管阻力的各种测量。尽管通气量高（4-71.min-1.kg-1），金枪鱼从吸入水中提取大约50%的氧气，部分原因是高心输出量（115-132 ml.min-1.kg-1）导致通气/灌注传导比（0.75-1.1）接近理论上理想值1.0。因此，金枪鱼的氧转移系数（ml O2.min-1.mmHg-1.kg-1）比其他鱼类高10-50倍。金枪鱼从水中转移氧气的效率（几乎等于65%）与硬骨鱼类中测量的通气量低一个数量级相匹配。金枪鱼的高氧转移因子部分是由于大的鳃表面积而成为可能;然而，这似乎带来了相当大的调节成本，因为鳃的代谢率可能占脊椎阻塞（即，不游泳的鱼。在缺氧期间，鲣鱼和黄鳍金枪鱼显示心率下降，通气量增加，其他硬骨鱼也是如此。然而，在金枪鱼中，缺氧性心动过缓并不伴随着每搏输出量的等量增加，心输出量福尔斯随着RR降低而下降。在这两种金枪鱼中，氧气消耗最终必须通过大量静脉氧气储备来维持。这发生在一个较高的吸入水PO 2（130和90毫米汞柱之间），鲣鱼金枪鱼比黄鳍金枪鱼（90和50毫米汞柱之间）。需要利用静脉氧气储备将难以满足增加游泳速度的氧气需求，这是两个物种对缺氧的共同反应。由于黄鳍金枪鱼可以在90毫米汞柱的海水氧分压下维持耗氧量，而不需要静脉氧气储备，因此它们可能在这种缺氧水平下存活很长时间。
Responses to acute hypoxia were measured in skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacures) (almost-equal-to 1-3 kg body weight). Fish were prevented from making swimming movements by a spinal injection of lidocaine and were placed in front of a seawater delivery pipe to provide ram ventilation of the gills. Fish could set their own ventilation volumes by adjusting mouth gape. Heart rate, dorsal and ventral aortic blood pressures, and cardiac output were continuously monitored during normoxia (inhalant water (PO2 > 150 mmHg) and three levels of hypoxia (inhalant water PO2 almost-equal-to 130, 90, and 50 mmHg). Water and blood samples were taken for oxygen measurements in fluids afferent and efferent to the gills. From these data, various measures of the effectiveness of oxygen transfer, and branchial and systemic vascular resistance were calculated. Despite high ventilation volumes (4-71.min-1.kg-1), tunas extract approximately 50% of the oxygen from the inhalant water, in part because high cardiac outputs (115-132 ml.min-1.kg-1) result in ventilation/perfusion conductance ratios (0.75-1.1) close to the theoretically ideal value of 1.0. Therefore, tunas have oxygen transfer factors (ml O2.min-1.mmHg-1.kg-1) that are 10-50 times greater than those of other fishes. The efficiency of oxygen transfer from water in tunas (almost-equal-to 65%) matches that measured in teleosts with ventilation volumes an order of magnitude lower. The high oxygen transfer factors of tunas are made possible, in part, by a large gill surface area; however, this appears to carry a considerable osmoregulatory cost as the metabolic rate of gills may account for up 70% of the total metabolism in spinally blocked (i.e., non-swimming) fish. During hypoxia, skipjack and yellowfin tunas show a decrease in heart rate and increase in ventilation volume, as do other teleosts. However, in tunas hypoxic bradycardia is not accompanied by equivalent increases in stroke volume, and cardiac output falls as RR decreases. In both tuna species, oxygen consumption eventually must be maintained by drawing on substantial venous oxygen reserves. This occurs at a higher inhalant water PO2 (between 130 and 90 mmHg) in skipjack tuna than in yellowfin tuna (between 90 and 50 mmHg). The need to draw on venous oxygen reserves would make it difficult to meet the oxygen demand of increasing swimming speed, which is a common response to hypoxia in both species. Because yellowfin tuna can maintain oxygen consumption at a seawater oxygen tension of 90 mmHg without drawing on venous oxygen reserves, they could probably survive for extended periods at this level of hypoxia.