Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL, USA.
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.
Mol Ecol. 2018 Apr;27(7):1621-1632. doi: 10.1111/mec.14547. Epub 2018 Apr 14.
Species inhabiting the North American west coast intertidal must tolerate an extremely variable environment, with large fluctuations in both temperature and salinity. Uncovering the mechanisms for this tolerance is key to understanding species' persistence. We tested for differences in salinity tolerance between populations of Tigriopus californicus copepods from locations in northern (Bodega Reserve) and southern (San Diego) California known to differ in temperature, precipitation and humidity. We also tested for differences between populations in their transcriptomic responses to salinity. Although these two populations have ~20% mtDNA sequence divergence and differ strongly in other phenotypic traits, we observed similarities in their phenotypic and transcriptomic responses to low and high salinity stress. Salinity significantly affected respiration rate (increased under low salinity and reduced under high salinity), but we found no significant effect of population on respiration or a population by salinity interaction. Under high salinity, there was no population difference in knock-down response, but northern copepods had a smaller knock-down under low salinity stress, corroborating previous results for T. californicus. Northern and southern populations had a similar transcriptomic response to salinity based on a principle components analysis, although differential gene expression under high salinity stress was three times lower in the northern population compared to the southern population. Transcripts differentially regulated under salinity stress were enriched for "amino acid transport" and "ion transport" annotation categories, supporting previous work demonstrating that the accumulation of free amino acids is important for osmotic regulation in T. californicus.
栖息在北美西海岸潮间带的物种必须耐受极其多变的环境，温度和盐度都有很大的波动。揭示这种耐受性的机制是理解物种持续存在的关键。我们测试了来自加利福尼亚北部（博德加保护区）和南部（圣地亚哥）的加利福尼亚桡足类（Tigriopus californicus）种群在盐度容忍度上的差异，这些种群已知在温度、降水和湿度方面存在差异。我们还测试了种群在盐度转录组反应方面的差异。尽管这两个种群的 mtDNA 序列差异约为 20%，并且在其他表型特征上差异很大，但我们观察到它们对低盐度和高盐度胁迫的表型和转录组反应存在相似之处。盐度显著影响呼吸速率（低盐度下增加，高盐度下减少），但我们没有发现种群对呼吸或种群与盐度相互作用的显著影响。在高盐度下，击倒反应没有种群差异，但北方桡足类在低盐度胁迫下的击倒幅度较小，这与之前对 T. californicus 的研究结果一致。北方和南方种群的盐度转录组反应基于主成分分析具有相似性，尽管在高盐度胁迫下北方种群的差异基因表达是南方种群的三倍。在盐度胁迫下差异调节的转录物富含“氨基酸转运”和“离子转运”注释类别，支持先前的工作表明，游离氨基酸的积累对 T. californicus 的渗透调节很重要。
