Deep-diving sea lions exhibit extreme bradycardia in long-duration dives
Deep-diving sea lions exhibit extreme bradycardia in long-duration dives
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DOI：
10.1242/jeb.098558
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发表时间：
2014-05-01
影响因子：
2.8
通讯作者：
Ponganis, Paul J.
中科院分区：
文献类型：
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作者：
McDonald, Birgitte I.;Ponganis, Paul J.
心率和外周血流分布是海洋恒温动物储氧利用率和模式以及最终屏气持续时间的主要决定因素。尽管如此，人们对海狮和海狗在潜水时如何调节心率（f（H））知之甚少。我们调查了五只成年雌性加州海狮（Zalophus californianus）在觅食过程中的潜水f（H），通过使用数字心电图（ECG）记录仪和时间深度记录仪对其进行测量。在所有的跳水动作中，下潜f（H）（心跳次数/持续时间; 50 +/- 9次/分钟（-1））与表面频率相比降低（113 +/- 5次/分（-1）），所有潜水的瞬时f（H）均低于静止（100米），包括：（1）f（H）的初始快速下降导致下降结束时跳水的最低瞬时f（H），在持续时间超过6分钟的跳水中，通常低于10次/min;（2）在下潜的底部，f（H）略有增加，约为10-40次/分（-1）;（3）在上浮过程中，f（H）逐渐增加，在浮出水面之前迅速增加。因此，深潜海狮的f（H）调节不仅仅是进行性心动过缓。在深潜后期下降过程中，极度心动过缓和推测的肺和外周血流量的相关减少应（a）有助于保存肺氧储存，（B）增加肌肉对肌红蛋白结合氧储存的依赖性，（c）保存血氧储存，（d）有助于限制深度氮的吸收。海狮深潜时的f（H）曲线可能是深潜海洋恒温动物的特征，它们靠灵感潜水，因为最近在帝企鹅（另一种靠灵感潜水的深潜者）中记录了类似的f（H）曲线。
Heart rate and peripheral blood flow distribution are the primary determinants of the rate and pattern of oxygen store utilisation and ultimately breath-hold duration in marine endotherms. Despite this, little is known about how otariids (sea lions and fur seals) regulate heart rate (f(H)) while diving. We investigated dive f(H) in five adult female California sea lions (Zalophus californianus) during foraging trips by instrumenting them with digital electrocardiogram (ECG) loggers and time depth recorders. In all dives, dive f(H) (number of beats/duration; 50 +/- 9 beats min(-1)) decreased compared with surface rates (113 +/- 5 beats min(-1)), with all dives exhibiting an instantaneous f(H) below resting (100 m) consisted of: (1) an initial rapid decline in f(H) resulting in the lowest instantaneous f(H) of the dive at the end of descent, often below 10 beats min-1 in dives longer than 6 min in duration; (2) a slight increase in f(H) to similar to 10-40 beats min(-1) during the bottom portion of the dive; and (3) a gradual increase in f(H) during ascent with a rapid increase prior to surfacing. Thus, f(H) regulation in deep-diving sea lions is not simply a progressive bradycardia. Extreme bradycardia and the presumed associated reductions in pulmonary and peripheral blood flow during late descent of deep dives should (a) contribute to preservation of the lung oxygen store, (b) increase dependence of muscle on the myoglobin-bound oxygen store, (c) conserve the blood oxygen store and (d) help limit the absorption of nitrogen at depth. This f(H) profile during deep dives of sea lions may be characteristic of deep-diving marine endotherms that dive on inspiration as similar f(H) profiles have been recently documented in the emperor penguin, another deep diver that dives on inspiration.