The mechanism of polyunsaturated fatty acid synthesis by pond snail and application for conservation of biodiversity.

必需脂肪酸包括20：5n3、20：4n6和22：6n3，被广泛认为是动物的重要营养物质。一般来说，这些脂肪酸被认为是由水生生态系统中的藻类产生的。在这项研究中，我们发现淡水蜗牛和鱼的鱼肉中含有这些必需的脂肪酸，即使这些脂肪酸在它们的食物来源中是不存在的。我们还发现，原生动物成群地出现在鱼体上，但几乎没有在食物来源上检测到原生动物，这是实验室实验中鱼体的原始特征。此外，原生动物密度与鱼体必需脂肪酸浓度呈显著正相关。这表明，鱼体中的必需脂肪酸可能归因于原生动物的存在。石块上成群的原生动物似乎提高了碎屑食物网中石块的营养质量。

Essential fatty acids including 20:5n3, 20:4n6 and 22:6n3 have been widely known as important nutrient for animals. Generally, these fatty acids have been considered to be produced by algal species in aquatic ecosystems. In this study, we found that feaces from freshwater snail and fish included these essential fatty acids even these fatty acids were absent in their food sources. We also found that protozoa swarmed on the feaces but almost no protozoa were detected on the food sources which was original of the feaces in the laboratory experiments. Moreover, significant positive relationship between density of protozoa and concentration of essential fatty acid in the feaces were confirmed. It indicate that essential fatty acid in feaces would be attributed to the presence of protozoa. Swarm of protozoa on the feaces seemed to enhance the nutritional quality of feaces in detrital food web.