Cyanobacterial blooms aggravate with increasing temperature, and the increased concentrations of toxicants such as cyanotoxins and nitrite during bloom decay adversely affect the growth of aquatic animals. Heat-shock proteins (Hsps) are induced by a wide range of environmental stressors, including temperature and toxicants. In this study, Brachionus calyciflorus Pallas was exposed to different combined solutions of microcystin-LR (0, 10, 30, and 100 µg L−1) and nitrite (0, 1, 3, and 5 mg L−1) to evaluate their effects on the rotifer lifespan, the reproductive rate (R), and the responses of four Hsp genes at 20 °C, 25 °C, and 30 °C. Results revealed that single high doses of microcystin-LR (100 µg L−1) and nitrite (5 mg L−1) were harmful to the lifespan and reproduction of rotifers. Hormesis was induced by low doses of microcystin-LR (10–30 µg L−1) and nitrite (1–3 mg L−1). At different toxicant concentrations, the expression levels of Hsp40, Hsp60, Hsp70, and Hsp90 fluctuated, whereas reactive oxygen species (ROS) levels increased regardless of temperature. The two toxicants induced high levels of ROS production, which negatively affected the lifespan, R, and Hsp gene expression at 30 °C (p < 0.05). Microcystin-LR and nitrite exerted synergistic effects on the lifespan, R, ROS levels, and Hsp gene expression levels at 20 °C and 25 °C (p < 0.05) but had antagonistic effects on Hsp40 and Hsp60 expression levels at 30 °C (p > 0.05). Temperature, microcystin-LR, and nitrite had interactive effects on the lifespan, R, ROS levels, and Hsp gene expression levels (p < 0.05). The expression levels of Hsp genes are useful biomarkers of high-temperature exposure, and Hsp-mediated heat shock responses are important in microcystin-LR and nitrite stress tolerance of B. calyciflorus.

中文翻译：

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微囊藻毒素-LR和亚硝酸盐对不同温度下轮虫寿命、繁殖和热激响应的影响

蓝藻水华随温度升高而加剧，水华衰变过程中蓝藻毒素和亚硝酸盐等毒物浓度的增加对水生动物的生长产生不利影响。热休克蛋白 (Hsps) 由多种环境压力因素诱导，包括温度和毒物。在本研究中，花臂腕轮藻暴露于微囊藻毒素-LR（0、10、30 和 100 µg L-1）和亚硝酸盐（0、1、3 和 5 mg L-1）的不同组合溶液中，以评估它们的对轮虫寿命、繁殖率 (R) 和四种 Hsp 基因在 20 °C、25 °C 和 30 °C 下的反应的影响。结果表明，单次高剂量微囊藻毒素-LR（100 µg L-1）和亚硝酸盐（5 mg L-1）对轮虫的寿命和繁殖有害。低剂量的微囊藻毒素-LR（10-30 µg L-1）和亚硝酸盐（1-3 mg L-1）可诱导兴奋作用。在不同的毒物浓度下，Hsp40、Hsp60、Hsp70 和 Hsp90 的表达水平波动，而活性氧 (ROS) 水平增加而与温度无关。这两种毒物诱导高水平的 ROS 产生，这对 30 °C 时的寿命、R 和 Hsp 基因表达产生负面影响（p < 0.05）。微囊藻毒素-LR 和亚硝酸盐在 20 °C 和 25 °C 下对寿命、R、ROS 水平和 Hsp 基因表达水平产生协同作用（p < 0.05），但在 30 °C 下对 Hsp40 和 Hsp60 表达水平有拮抗作用（ p > 0.05）。温度、微囊藻毒素-LR 和亚硝酸盐对寿命、R、ROS 水平和 Hsp 基因表达水平具有交互作用（p < 0.05）。