Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, Canada, R3T 2N2.
Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, Canada, M4A 1AC.
J Exp Biol. 2023 May 15;226(10). doi: 10.1242/jeb.245335. Epub 2023 May 19.
Chronic exposure to high temperatures may leave freshwater fishes vulnerable to opportunistic pathogens, particularly during early life stages. Lake sturgeon, Acipenser fulvescens, populations within the northern expanse of their range in Manitoba, Canada, may be susceptible to high temperature stress and pathogenic infection. We acclimated developing lake sturgeon for 22 days to two ecologically relevant, summer temperatures (16 and 20°C). Individuals from both acclimation treatments were then exposed to 0, 30 and 60 µg ml-1 bacterial lipopolysaccharides (endotoxins), as an immune stimulus, for 48 h and sampled 4 and 48 h during trial exposures and following a 7 day recovery period. We then measured whole-body transcriptional (mRNA) responses involved in the innate immune, stress and fatty acid responses following acute exposure to the bacterial endotoxins. Data revealed that overall levels of mRNA transcript abundance were higher in 20°C-reared sturgeon under control conditions. However, following exposure to a bacterial stimulus, lake sturgeon acclimated to 16°C produced a more robust and persistent transcriptional response with higher mRNA transcript abundance across innate immune, stress and fatty acid responses than their 20°C-acclimated counterparts. Additional whole-animal performance metrics (critical thermal maximum, metabolic rate, cortisol concentration and whole-body and mucosal lysozyme activity) demonstrated acclimation-specific responses, indicating compromised metabolic, stress and enzymatic capacity following the initiation of immune-related responses. Our study showed that acclimation to 20°C during early development impaired the immune capacity of developing lake sturgeon as well as the activation of molecular pathways involved in the immune, stress and fatty acid responses. The present study highlights the effects of ecologically relevant, chronic thermal stress on seasonal pathogen susceptibility in this endangered species.
慢性暴露于高温可能会使淡水鱼类容易受到机会性病原体的侵害，尤其是在生命早期阶段。加拿大马尼托巴省北部地区的湖鲟（Acipenser fulvescens）种群可能容易受到高温胁迫和致病感染。我们将发育中的湖鲟适应 22 天，适应两种具有生态相关性的夏季温度（16 和 20°C）。然后，来自两种适应处理的个体暴露于 0、30 和 60 µg ml-1 细菌脂多糖（内毒素），作为免疫刺激物，持续 48 小时，并在试验暴露期间和 7 天恢复期内采样 4 和 48 小时。然后，我们测量了急性暴露于细菌内毒素后参与固有免疫、应激和脂肪酸反应的全身转录（mRNA）反应。数据表明，在对照条件下，20°C 饲养的鲟鱼的整体 mRNA 转录丰度水平较高。然而，在暴露于细菌刺激物后，适应 16°C 的湖鲟产生了更强大和持久的转录反应，与适应 20°C 的湖鲟相比，固有免疫、应激和脂肪酸反应的 mRNA 转录丰度更高。其他全动物性能指标（临界热最大值、代谢率、皮质醇浓度以及全身和黏膜溶菌酶活性）表明了适应的特异性反应，表明在免疫相关反应开始后，代谢、应激和酶能力受损。我们的研究表明，在早期发育过程中适应 20°C 会损害发育中的湖鲟的免疫能力，以及参与免疫、应激和脂肪酸反应的分子途径的激活。本研究强调了与生态相关的慢性热应激对这一濒危物种季节性病原体易感性的影响。
