Verhille Christine E, Dabruzzi Theresa F, Cocherell Dennis E, Mahardja Brian, Feyrer Fred, Foin Theodore C, Baerwald Melinda R, Fangue Nann A
Department of Wildlife, Fish, and Conservation Biology, University of California, 1 Shields Ave., Davis, CA 95616, USA.
Department of Ecology, Montana State University, 310 Lewis Hall ,Bozeman, MT 59717, USA.
Conserv Physiol. 2020 Dec 10;8(1):coaa098. doi: 10.1093/conphys/coaa098. eCollection 2020.
The Sacramento splittail () is composed of two genetically distinct populations endemic to the San Francisco Estuary (SFE). The allopatric upstream spawning habitat of the Central Valley (CV) population connects with the sympatric rearing grounds via relatively low salinity waters, whereas the San Pablo (SP) population must pass through the relatively high-salinity Upper SFE to reach its allopatric downstream spawning habitat. We hypothesize that if migration through SFE salinities to SP spawning grounds is more challenging for adult CV than SP splittail, then salinity tolerance, osmoregulatory capacity, and metabolic responses to salinity will differ between populations. Osmoregulatory disturbances, assessed by measuring plasma osmolality and ions, muscle moisture and Na-K-ATPase activity after 168 to 336 h at 11‰ salinity, showed evidence for a more robust osmoregulatory capacity in adult SP relative to CV splittail. While both resting and maximum metabolic rates were elevated in SP splittail in response to increased salinity, CV splittail metabolic rates were unaffected by salinity. Further, the calculated difference between resting and maximum metabolic values, aerobic scope, did not differ significantly between populations. Therefore, improved osmoregulation came at a metabolic cost for SP splittail but was not associated with negative impacts on scope for aerobic metabolism. These results suggest that SP splittail may be physiologically adjusted to allow for migration through higher-salinity waters. The trends in interpopulation variation in osmoregulatory and metabolic responses to salinity exposures support our hypothesis of greater salinity-related challenges to adult CV than SP splittail migration and are consistent with our previous findings for juvenile splittail populations, further supporting our recommendation of population-specific management.
萨克拉门托裂尾鱼（）由旧金山湾（SFE）特有的两个基因不同的种群组成。中央谷地（CV）种群的异域上游产卵栖息地通过盐度相对较低的水域与同域育幼场相连，而圣巴勃罗（SP）种群必须穿过盐度相对较高的旧金山湾上游才能到达其异域下游产卵栖息地。我们假设，如果成年CV裂尾鱼通过旧金山湾盐度迁移到SP产卵地比SP裂尾鱼更具挑战性，那么种群之间的耐盐性、渗透调节能力和对盐度的代谢反应将会有所不同。在11‰盐度下168至336小时后，通过测量血浆渗透压和离子、肌肉水分和钠钾ATP酶活性来评估渗透调节紊乱，结果表明成年SP裂尾鱼相对于CV裂尾鱼具有更强的渗透调节能力。虽然随着盐度增加，SP裂尾鱼的静息代谢率和最大代谢率均升高，但CV裂尾鱼的代谢率不受盐度影响。此外，计算得出的静息代谢值与最大代谢值之间的差异，即有氧代谢范围，在种群之间没有显著差异。因此，改善渗透调节对SP裂尾鱼来说是以代谢为代价的，但与对有氧代谢范围的负面影响无关。这些结果表明，SP裂尾鱼可能在生理上进行了调整，以适应通过盐度更高的水域进行迁移。对盐度暴露的渗透调节和代谢反应的种群间差异趋势支持了我们的假设，即成年CV裂尾鱼比SP裂尾鱼在迁移过程中面临更大的与盐度相关的挑战，这与我们之前对幼体裂尾鱼种群的研究结果一致，进一步支持了我们针对特定种群进行管理的建议。
