Sardella Brian A, Kültz Dietmar
Department of Animal Science, University of California, Davis, One Shields Avenue, Davis, California 95616.
Physiol Biochem Zool. 2014 May-Jun;87(3):456-63. doi: 10.1086/675494. Epub 2014 Mar 6.
The green sturgeon (Acipenser medirostris) is an anadromous species with a distinct population segment in the San Francisco Bay-Sacramento River Delta that is currently listed as threatened. Although this species is able to tolerate salinity challenges as soon as 6 mo posthatch, its ability to deal with unpredictable salinity fluctuations remains unknown. Global climate change is predicted to result in large freshwater (FW) flushes through the estuary during winter and greater tidal influence during the summer. We exposed green sturgeon acclimated to 15 (EST) or 24 (BAY) g/L salinity to a rapid FW influx, where salinity was reduced to 0 g/L in 3 h in order to simulate the effect of the "winter" scenario. Both groups survived, enduring a 10% plasma osmolality reduction after 3 h. BAY-acclimated sturgeon upregulated both Na(+), K(+)-ATPase (NKA) activity and caspase 3/7 activity, but no changes were observed in the EST-acclimated fish. In addition, we exposed FW-acclimated sturgeon to a dual 12-h salinity fluctuation cycle (0-24-0 g/L) in order to simulate the effect of greater tidal influence. At 6 h, the sturgeon showed a significant increase in plasma osmolality, and branchial NKA and caspase 3/7 activities were increased, indicating an acclimation response. There was no acclimation at 18 h, and plasma osmolality was higher than the peak observed at 6 h. The second fluctuation elicited an upregulation of the stress proteins ubiquitin and heat shock 70-kDa protein (HSP 70). Sturgeon can acclimate to changes in salinity; however, salinity fluctuations resulted in substantial cellular stress.
绿鲟（Acipenser medirostris）是一种溯河洄游性物种，在旧金山湾 - 萨克拉门托河三角洲有一个独特的种群，目前被列为受威胁物种。尽管该物种在孵化后6个月就能耐受盐度挑战，但其应对不可预测盐度波动的能力仍不为人知。预计全球气候变化将导致冬季大量淡水涌入河口，夏季潮汐影响增强。我们将适应15（EST）或24（BAY）g/L盐度的绿鲟暴露于快速淡水涌入环境中，在3小时内将盐度降至0 g/L，以模拟“冬季”情景的影响。两组均存活，3小时后血浆渗透压降低了10%。适应BAY盐度的鲟鱼上调了钠钾ATP酶（NKA）活性和半胱天冬酶3/7活性，但适应EST盐度的鱼未观察到变化。此外，我们将适应淡水的鲟鱼暴露于12小时的双盐度波动周期（0 - 24 - 0 g/L）中，以模拟更大潮汐影响的效果。在6小时时，鲟鱼血浆渗透压显著升高，鳃NKA和半胱天冬酶3/7活性增加，表明有适应反应。18小时时没有适应现象，血浆渗透压高于6小时观察到的峰值。第二次波动引起应激蛋白泛素和热休克70 kDa蛋白（HSP 70）上调。鲟鱼能够适应盐度变化；然而，盐度波动会导致大量细胞应激。
