Genetic Study on Variation among Strains of the Rotifer Brachionus plicatilis.

我们收集了67个轮虫品系（褶皱臂尾轮虫）来自世界各地，包括日本。首先根据洛里卡前棘的形态差异，将这些品系分为两型（L型，30只; S型，37只）。然后，对于每个品系，从一个个体繁殖的20个个体在7个身体部位和5个品种中进行形态计量学测量，当它们长大直到产下第一个卵时。聚类分析表明，67个菌株可分为两大类，每一类仅由L型或S型菌株组成，以少量冻存液作为粗酶液，采用水平淀粉凝胶电泳法对67个菌株的同工酶进行了分析。6种酶的6个位点可作为同工酶。L型和S型在6个位点的23个等位基因上的同工酶变异存在较大差异。根据46个等位基因频率的遗传距离，绘制了67个菌株的聚类图。菌株可分为两组，每组仅由S型或L型菌株组成。结果表明，L型和S型菌株之间存在较大的遗传差异，在37株S型菌株中，有4株菌株的同工酶谱与其它S型菌株不同。在这些菌株中，有三个位点是特殊的同工酶谱。形态计量学研究表明，洛里卡的大小远远大于平均值的37个S型菌株。这四个菌株可能是三倍体。

We collected 67 rotifer strains ( Brachionus plicatilis ) from many localities all over the world, including Japan. At first, we divided these strains into two types (L,30; S,37) by judging morphologically with the shape difference of anterior spines in lorica. Then, for each strain, 20 individuals which multiplied from one individual were measured morphometrically in 7 body parts and 5 varieties, when they grew up until laying the first eggs. The cluster analysis indicated that 67 strains can be divided into two large clusters, each of which consist only of group of L or S strains.Isozyme variations of 67 strains were detected by horizontal starch gel electrophoresis with a little amount of drip thawed from frozen stock as a crude enzyme. Six loci on 6 enzymes were interpretable as isozyme. Large differences in isozyme variation on 23 allele on 6 loci were recognized between L and S types. From genetic distances according to gene frequencies of 46 allele, the dendrogram among 67 strains was drawn. The strains were divided into two groups, each of which consists only of S type or L type strains. This result indicates the great genetical differences between L and S type strains.Among 37 S type strains, four strains showed isozyme patterns different from other S type strains. In these strains, three loci were particular for isozyme patterns. Morphometric studies showed that lorica sizes were much larger than the mean of 37 S type strains. The four strains might be triploid.