Allen Peter J, Haukenes Alf, Lochmann Steve E
Department of Wildlife, Fisheries and Aquaculture, Mississippi State University, PO Box 9690, Mississippi State, MS 39762, United States.
Center for Aquaculture and Fisheries, University of Arkansas Pine Bluff, PO Box 4912, Pine Bluff, AR 71601, United States.
Comp Biochem Physiol A Mol Integr Physiol. 2017 Jul;209:16-24. doi: 10.1016/j.cbpa.2017.04.003. Epub 2017 Apr 8.
The alligator gar Atractosteus spatula is a primitive fish species, occupying a wide range of temperature and salinity habitats. Long-distance movements are limited, leading to genetic differentiation between inland and coastal populations. Unknown is whether physiological capacity differs between geographically separated populations, particularly for traits important to osmoregulation in saline environments. Alligator gar from inland and coastal populations were reared in a similar environment and exposed to temperature (10, 30°C) and salinity (0, 20ppt) extremes to determine whether iono- and osmoregulatory ability differed between populations. There were few differences in osmoregulatory ability between populations, with similar gill, blood and gastrointestinal tract osmoregulatory parameters. Blood plasma osmolality, ion concentrations, intestinal pH and bicarbonate base concentrations, intestinal fluid osmolality, ion concentrations and gill Na, K-ATPase (NKA) activity were similar between populations. Notably, gar from both populations did not osmoregulate well at low temperature and high salinity, with elevated plasma osmolality and ion concentrations, low gill NKA, and little evidence of gastrointestinal tract contribution to ionic and base regulation based on a lack of intestinal fluid and low base content. Therefore, the hypothesis that coastal gar would have improved osmotic regulatory ability in saline environments as compared to inland alligator gar was not supported, suggesting physiological capacity may be retained in primitive species possibly due to its importance to their persistence through time.
钝吻古鳄（Atractosteus spatula）是一种原始鱼类，栖息于广泛的温度和盐度环境中。其远距离移动受限，导致内陆和沿海种群之间产生遗传分化。目前尚不清楚地理隔离的种群之间生理能力是否存在差异，特别是在盐环境中对渗透调节至关重要的特征方面。将来自内陆和沿海种群的钝吻古鳄在相似环境中饲养，并使其暴露于温度（10、30°C）和盐度（0、20ppt）极端条件下，以确定不同种群之间的离子和渗透调节能力是否存在差异。不同种群之间的渗透调节能力差异不大，鳃、血液和胃肠道的渗透调节参数相似。不同种群之间的血浆渗透压、离子浓度、肠道pH值和碳酸氢盐碱浓度、肠液渗透压、离子浓度以及鳃钠钾ATP酶（NKA）活性相似。值得注意的是，来自两个种群的钝吻古鳄在低温和高盐度条件下的渗透调节能力都不佳，表现为血浆渗透压和离子浓度升高、鳃NKA活性降低，并且基于肠液缺乏和碱含量低，几乎没有证据表明胃肠道对离子和碱调节有贡献。因此，与内陆钝吻古鳄相比，沿海钝吻古鳄在盐环境中具有更好的渗透调节能力这一假设未得到支持，这表明生理能力可能在原始物种中得以保留，这可能是由于其对物种长期生存的重要性。
