Pousse Émilien, Flye-Sainte-Marie Jonathan, Alunno-Bruscia Marianne, Hégaret Hélène, Jean Fred
Université de Bretagne Occidentale (UBO), UMR 6539 LEMAR, IUEM, Technopôle Brest-Iroise, Rue Dumont d'Urville, 29280 Plouzané, France; Ifremer, UMR 6539 LEMAR, 11 presqu'île du Vivier, 29840 Argenton-en-Landunvez, France.
Université de Bretagne Occidentale (UBO), UMR 6539 LEMAR, IUEM, Technopôle Brest-Iroise, Rue Dumont d'Urville, 29280 Plouzané, France.
Toxicon. 2018 Mar 15;144:14-22. doi: 10.1016/j.toxicon.2017.12.050. Epub 2017 Dec 27.
This study was designed to assess the contribution of feeding behavior to inter-individual variability of paralytic shellfish toxin (PST) accumulation in the Pacific oyster Crassostrea gigas. For this purpose 42 oysters were exposed for 2 days to non-toxic algae and then for 2 other days to the PST producer Alexandrium minutum. Individual clearance rate (CR) of oysters was continuously monitored over the 4 days using an ecophysiological measurement system. Comparison of CR values when exposed to toxic and non toxic algae allowed to estimate a clearance rate inhibition index (CRII). Toxin concentration of oysters was quantified at the end of the experiment. These data allowed to estimate the toxin accumulation efficiency (TAE) as the ratio of toxin accumulated on toxin consumed. Changes of clearance rate during the experiment indicated that all individuals stopped feeding immediately after being exposed to A. minutum for at least 7 h. This fast response likely corresponded to a behavioral mechanism of avoidance rather to a toxin-induced response. Individuals also showed high inter-variability in their recovery of filtration after this period. Most of the inter-individual variability (78%) in PST accumulation in C. gigas could be explained by the consumption of A. minutum cells, thus emphasizing the importance of the feeding behavior in accumulation. Based on the toxin concentration in their tissues, oysters were clustered in 3 groups showing contrasted patterns of PST accumulation: the high accumulation group was characterized by high feeding rates both on non-toxic and toxic diet and subsequently a low CRII and high TAE. Inversely, the low accumulation group was characterized by low filtration rates, high CRII and low TAE. Both filtration capacity and sensitivity of oysters to toxins may account for the differences in their accumulation. The contribution of TAE in PST accumulation is discussed and might result from differences in assimilation and detoxification abilities among individuals.
本研究旨在评估摄食行为对太平洋牡蛎（Crassostrea gigas）中麻痹性贝类毒素（PST）积累个体间差异的影响。为此，将42只牡蛎先暴露于无毒藻类2天，然后再暴露于产PST的微小亚历山大藻（Alexandrium minutum）2天。使用生态生理测量系统在4天内持续监测牡蛎的个体清除率（CR）。通过比较暴露于有毒和无毒藻类时的CR值来估算清除率抑制指数（CRII）。在实验结束时对牡蛎的毒素浓度进行定量。这些数据使得能够将毒素积累效率（TAE）估算为积累的毒素与消耗的毒素之比。实验过程中清除率的变化表明，所有个体在暴露于微小亚历山大藻至少7小时后立即停止摄食。这种快速反应可能对应于一种回避行为机制，而非毒素诱导的反应。在此期间之后，个体在滤食恢复方面也表现出高度的个体间差异。太平洋牡蛎中PST积累的个体间差异大部分（78%）可以由微小亚历山大藻细胞的消耗来解释，从而强调了摄食行为在积累中的重要性。根据其组织中的毒素浓度，牡蛎被聚类为3组，呈现出对比鲜明的PST积累模式：高积累组的特征是在无毒和有毒食物上的摄食率都很高，随后CRII较低且TAE较高。相反，低积累组的特征是滤食率低、CRII高且TAE低。牡蛎的滤食能力和对毒素的敏感性可能是其积累差异的原因。文中讨论了TAE在PST积累中的作用，这可能源于个体间同化和解毒能力的差异。
