No consistent explanation has been found for the variability in the thiaminase activity of alewives Alosa pseudoharengus despite the role of alewife thiaminase in large-scale salmonine mortality in the Laurentian Great Lakes. We conducted experiments to evaluate the effect of two stressors, reduced salt content in the water and food limitation, on alewife thiaminase activity. Alewives were subjected to treatments in replicated tanks in which conductivity was lowered (< 100 microS/cm) for 8 d and feeding was limited for 39 d. Circulating white blood cells, plasma cortisol, plasma glucose, and whole-body thiaminase were measured in individual alewives to assess their response to these experimental treatments. Alewives from the controls had significantly larger numbers of circulating white blood cells than those in the salt-reduced and food-limited treatments (24,000 and 19,000 cells/microL and 11,000 and 9,000 cells/microL for alewives from the two control and salt-reduced treatment tanks, respectively, and 34,000 and 30,000 cells/microL and 21,000 and 16,000 cells/microL for alewives from the two control and food-limited treatment tanks). No significant differences in alewife thiaminase activity were found between treatment fish and their controls. The mean thiaminase activity in the alewives studied increased from 6,900 to 16,000 pmol x g(-1) x min(-1) from the time of their collection in Cayuga Lake to the start of laboratory experiments 1.5-2.5 years later; the latter value was more than twice that of previously reported levels of thiaminase activity from alewives collected in the wild. These data suggest that the variability in alewife thiaminase is not related to stress from salt reduction or food limitation, but laboratory holding conditions significantly increased thiaminase through a mechanism not evaluated by our experimental treatments.

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评估压力源对 Alewife 硫胺酶活性的影响

尽管 alewife 硫胺酶在 Laurentian Great Lakes 的大规模鲑鱼死亡中发挥作用，但尚未发现对 alewives Alosa pseudoharengus 硫胺酶活性的变异性的一致解释。我们进行了实验来评估两种压力因素，即减少水中盐分含量和食物限制对 alewife 硫胺酶活性的影响。Alewives 在重复的罐中进行处理，其中电导率降低 (< 100 microS/cm) 8 天，饲养限制 39 天。测量个体 alewives 的循环白细胞、血浆皮质醇、血浆葡萄糖和全身硫胺酶，以评估它们对这些实验治疗的反应。来自对照组的白细胞的循环白细胞数量明显多于减盐和限食治疗中的循环白细胞数量（24,000 和 19,000 个细胞/微升，来自两个对照和减盐处理的 11,000 和 9,000 个细胞/微升）分别为 34,000 和 30,000 个细胞/微升和 21,000 和 16,000 个细胞/微升，用于来自两个对照和食物限制处理池的 alewives）。在处理鱼和它们的对照之间没有发现 alewife 硫胺素酶活性的显着差异。研究的 alewives 中的平均硫胺酶活性从 6,900 增加到 16,000 pmol xg(-1) x min(-1)，从它们在 Cayuga 湖采集到 1.5-2.5 年后实验室实验开始；后者的值是先前报告的野生白鲟的硫胺酶活性水平的两倍多。这些数据表明 alewife 硫胺素酶的变异性与减盐或食物限制引起的压力无关，但实验室保持条件通过我们的实验处理未评估的机制显着增加了硫胺素酶。