Dép. Sciences Biologiques, Université du Québec à Montréal (UQAM), C.P. 8888, Succ. Centre-Ville, Montréal, QC, Canada H3C 3P8.
Aquat Toxicol. 2011 May;103(1-2):63-70. doi: 10.1016/j.aquatox.2011.02.006. Epub 2011 Feb 18.
Although accumulation of the liver toxin microcystin in phytoplanktivorous fish has been demonstrated in captive fish and in natural ecosystems, the relation between microcystin in ingested algae and the pattern of buildup of microcystin in fish is poorly known. In this month-long study performed at a Brazilian fish farm, 45 mature Oreochromis niloticus were fed daily with fresh seston periodically dominated by toxic Microcystis sp. Microcystin was measured daily in the food and every 5 days in liver and muscle samples. Control fish received a diet of seston that was low in toxic cyanobacteria. Initially, in treatment ponds, microcystin available for fish increased from 6.5 to 66.9 ng microcystin fish(-1)day(-1), which was accompanied by an increase from 5.5 to 35.4 ng microcysting liver(-1). Microcystin in muscle was below our detection limit of 4 ng g tissue(-1) for the entire study. In the bloom phase, available microcystin reached its highest concentration (4450 ng MC fish(-1)day(-1)) then decreased to 910 ng microcystin fish(-1)day(-1) on day 31. During this period, microcystin reached its highest concentration of 81.6 ng MC g liver(-1) and stayed high until the end of the experiment. A model based on rapid uptake, saturation, and exponential loss was built with these experimental results, and verified with data from the literature. Our model showed that accumulation was up to 50% of ingestion at low doses, but at intermediate doses, the onset of elimination led to a decline of liver burden. Although the accumulation rate confirms the high contamination potential of microcystin, it was balanced by a high depuration rate and this efficient systemic elimination may explain the tolerance of these fish to toxic blooms in the wild.
虽然已经在人工养殖的鱼类和自然生态系统中证明了摄食的藻类中存在肝毒素微囊藻毒素，但微囊藻毒素在藻类中的积累与鱼类中微囊藻毒素的积累模式之间的关系尚不清楚。在巴西的一个鱼类养殖场进行的为期一个月的研究中，每天给 45 条成熟的奥利亚罗非鱼投喂新鲜的食物（藻类），这些食物周期性地以有毒的微囊藻为主。每天测量食物中的微囊藻毒素，每 5 天测量一次鱼肝和肌肉样本中的微囊藻毒素。对照组鱼的食物中含有低浓度的有毒蓝藻。在治疗池中，供鱼类食用的微囊藻毒素含量从最初的 6.5 增加到 66.9 ng 微囊藻毒素鱼(-1)天(-1)，同时肝中微囊藻毒素含量从 5.5 增加到 35.4 ng 微囊藻毒素鱼(-1)。在整个研究期间，肌肉中的微囊藻毒素都低于我们检测限 4 ng g 组织(-1)。在水华高峰期，可利用的微囊藻毒素浓度达到最高（4450 ng MC 鱼(-1)天(-1)），然后在第 31 天降至 910 ng 微囊藻毒素鱼(-1)天(-1)。在此期间，微囊藻毒素达到肝中最高浓度 81.6 ng MC g 肝(-1)，并一直保持到实验结束。根据这些实验结果和文献中的数据，建立了一个基于快速吸收、饱和和指数损失的模型，并对其进行了验证。我们的模型表明，在低剂量时，积累量达到摄入量的 50%，但在中等剂量时，消除作用的开始导致肝负荷下降。尽管积累率证实了微囊藻毒素的高污染潜力，但高净化率使其得到平衡，这种有效的系统消除可能解释了这些鱼类对野外有毒水华的耐受性。
