Effect of manganese accumulation on the survival of juvenile short neck clam, Ruditapes philippinarum in the sandy tidal flat of Ariake Bay, Kyushu, Japan.

一、野外研究在锰含量较高的Arao潮滩三个研究区（A：近海沙覆盖区，C：未覆盖区，C：A和C之间的中间区），对菲律宾蛤仔（Ruditapes philippinalum）幼蛤的定居、生长和存活进行了追踪。在沉积物和间隙水中的锰中，可溶性锰含量较高，可溶性锰含量与幼鱼死亡率呈显著正相关。估算了间隙水锰离子浓度对文蛤幼贝死亡的阈值为60 mg/L以上。（2）通过饲养实验缩小死亡因子，锰离子浓度超过60 mg/L对文蛤幼贝也没有致死作用。但在含锰的养殖水中添加底泥后，成活率下降。此外，用沉积物-锰离子混合水的上层透明层饲养，死亡率有所提高 ...更多信息 呃，而用有机游离砂饲养，则没有致死作用。这些结果表明，幼蚌的死亡是由于沉积物中的可溶性锰与某些有机质发生反应而引起的。III.细胞培养生物测定为了随时进行野外调查或养殖试验所缩小的因素的暴露试验，我们尝试建立细胞培养生物测定体系。然而，脊椎动物的导流细胞培养技术对文蛤部分无效。另一方面，用爪蟾肝细胞进行的侧支实验表明，Mn离子对爪蟾卵黄发生有一定的抑制作用。四、文蛤幼贝的病理学研究虽然在光镜下进行了详细的观察，但在文蛤幼贝的切片中没有发现明显的病理学变化。我们一直在进行TEM观测。另一方面，我们准备使用MALDI-TOF MS来检查幼蛤的分泌肽。如果从Arao潮滩（高锰浓度）和菊池河口（低锰浓度）收集的幼蛤之间检测到肽分泌的任何差异，则将通过原位杂交来检测相应的分泌细胞。在上述实验中，我们发现饲养实验中高死亡率组的贝壳变脆，Arao种群也是如此。据认为，在高Mn条件下，在壳形成过程中引起了问题。我们目前正在进行的检查，适用于重点壳的形成：壳的强度，壳的微观结构，壳形成细胞在地幔。少

I.Field researchSettlement, growth and survival of juvenile clams (Ruditapes philippinalum) were traced at three research areas (A : covered with sand collected from the offshore, C : uncovered area, C : medium area between A and C) in Arao Tidal Flat where Manganese concentration of sand is very high. Among the Mn collected from the sediment and interstitial water, soluble Mn was quantified, and there was significant relationship between the concentration of soluble Mn and the mortality of juvenile calms. The threshold Mn ion concentration of the interstitial water for the extinction of juvenile clam was estimated to be over 60 mg/L.II.Narrowing down the death factor by rearing experiment.Mn ion did not have a lethal effect for the juvenile clams even if the concentration was over 60 mg/L. However, the survival rate decreased when the sediment was added to the rearing water with Mn ion. In addition, the mortality raised when reared with top clear layer of the sediment-Mn ion mixed wat … More er, whilst no lethal effect when reared with organic free sand. These results suggest that the death of juvenile clams are caused by the reaction between the soluble manganese and some organic matter in the sediment.III.Bioassay by cell cultureIn order to carry out the exposure experiment about the factors narrowed down by field research or rearing experiment at any time, we tried to establish the bioassay system by cell culture. However, diversion cell culture technology of vertebrates was partly ineffective for clams. On the other hand, the collateral experiment using Xenopus hepatocyte suggested that Mn ion had some inhibiting effect on the vitellogenesis of Xenopus.IV.Pathological study of juvenile clams.Although detail observation was carried out under the light microscope, no obvious pathological change was detected in the sections of juvenile clams. We are continuously carrying out TEM observation. On the other hand, we prepared to review secreted peptides in juvenile clams by using MALDI-TOF MS. If any difference of peptide secretion was detected between the juvenile clams collected from Arao Tidal Flat (high Mn concentration) and Kikuchi River Moouth (low Mn concentration), corresponding secretion cell will be detected by In situ hybridization. During the above experiment, we found that shell of the high mortality group in the rearing experiment became fragile, and so on about Arao population. It is thought that trouble is caused in the process of the shell formation under the high Mn condition. We are currently carrying out the examination that applies the focus to the shell formation : shell strength, microstructure of the shell, shell formation cells in the mantle. Less