Zena Lucas A, Bícego Kênia C, da Silva Glauber S F, Giusti Humberto, Glass Mogens L, Sanchez Adriana P
Department of Animal Morphology and Physiology, College of Agricultural and Veterinary Sciences, São Paulo State University, Jaboticabal, SP 14884-900, Brazil; National Institute of Science and Technology in Comparative Physiology (INCT Fisiologia Comparada), Brazil.
Department of Animal Morphology and Physiology, College of Agricultural and Veterinary Sciences, São Paulo State University, Jaboticabal, SP 14884-900, Brazil; National Institute of Science and Technology in Comparative Physiology (INCT Fisiologia Comparada), Brazil.
J Therm Biol. 2017 Jan;63:112-118. doi: 10.1016/j.jtherbio.2016.12.001. Epub 2016 Dec 6.
The South American lungfish, Lepidosiren paradoxa inhabits seasonal environments in the Central Amazon and Paraná-Paraguay basins that undergo significant oscillations in temperature throughout the year. They rely on different gas exchange organs, such as gills and skin for aquatic gas exchange while their truly bilateral lungs are responsible for aerial gas exchange; however, there are no data available on the individual contributions of the skin and the gills to total aquatic gas exchange in L. paradoxa. Thus, in the present study we quantify the relative contributions of skin and gills on total aquatic gas exchange during warm (35°C) and cold exposure (20°C) in addition to the effects of aerial and aquatic hypercarbia on aquatic gas exchange and gill ventilation rate (f; 25°C), respectively. Elevated temperature (35°C) caused a significant increase in the contribution of cutaneous (from 0.61±0.13 to 1.34±0.26ml. STPD.hkg) and branchial (from 0.54±0.17 to 1.73±0.53ml. STPD.hkg) gas exchange for V̇CO relative to the lower temperature (20°C), while V̇O remained relatively unchanged. L. paradoxa exhibited a greater branchial contribution in relation to total aquatic gas exchange at lower temperatures (20 and 25°C) for oxygen uptake. Aerial hypercarbia decreased branchial V̇O whereas branchial V̇CO was significantly increased. Progressive increases in aquatic hypercarbia did not affect f. This response is in contrast to increases in pulmonary ventilation that may offset any increase in arterial partial pressure of CO owing to CO loading through the animals' branchial surface. Thus, despite their reduced contribution to total gas exchange, cutaneous and branchial gas exchange in L. paradoxa can be significantly affected by temperature and aerial hypercarbia.
南美肺鱼（Lepidosiren paradoxa）栖息于亚马孙河中部和巴拉那 - 巴拉圭河流域的季节性环境中，这些地区全年温度波动显著。它们依靠不同的气体交换器官，如鳃和皮肤进行水生气体交换，而其真正的双侧肺则负责空气呼吸的气体交换；然而，目前尚无关于南美肺鱼皮肤和鳃对总水生气体交换的个体贡献的数据。因此，在本研究中，我们除了分别研究空气和水生高碳酸血症对水生气体交换和鳃通气率（f；25°C）的影响外，还量化了皮肤和鳃在温暖（35°C）和寒冷暴露（20°C）期间对总水生气体交换的相对贡献。相对于较低温度（20°C），温度升高（35°C）导致相对于V̇CO，皮肤（从0.61±0.13增加到1.34±0.26ml·STPD·h·kg）和鳃（从0.54±0.17增加到1.73±0.53ml·STPD·h·kg）气体交换的贡献显著增加，而V̇O相对保持不变。在较低温度（20和25°C）下，南美肺鱼在氧气摄取方面，鳃对总水生气体交换的贡献更大。空气高碳酸血症降低了鳃的V̇O，而鳃的V̇CO显著增加。水生高碳酸血症的逐渐增加并未影响f。这种反应与肺通气增加形成对比，肺通气增加可能抵消由于通过动物鳃表面加载CO导致的动脉血CO分压的任何增加。因此，尽管皮肤和鳃对总气体交换的贡献减少，但南美肺鱼的皮肤和鳃气体交换会受到温度和空气高碳酸血症的显著影响。
