Studies on the species evolution in Paramecium caudatum

为了研究草履虫的物种进化，需要不同地理位置的许多天然菌株，并通过恢复丢失的同基因（遗传物种）来建立。因此，我在美国、加拿大和乌拉圭进行了自然菌株的收集。在五大湖和美国东部地区的197个点和乌拉圭共和国的78个点进行了收集。从34个采样点获得尾状假单胞菌，建立了222条分离线.发现了三个具有互补交配型的类群，即“同基因”。这三个同基因独立于已知的同基因。它们暂被命名为合成基因a、合成基因B和合成基因d。还获得了属于同基因1、同基因3、同基因5和同基因12的新菌株.令人惊讶的是，从一些菌株例如UC 131或UC 151的分析中揭示了物种鉴定中的问题。它们在细胞大小和外部形态上与尾状原核菌非常相似，但其RAPD图谱与许多尾状原核菌菌株有很大差异。它们有2-5个泡状微核，两个收缩泡，生活在淡水中。这些特征与已知的生物物种不同。它们是否真的是新的生物物种，还需要进一步的研究。有些菌株表现出同基因间交配反应。这一证据强调了建立同基因标准菌株的重要性。

To study the species evolution in Paramecium caudatum, many natural strains at different geographic places are necessary, and establishment by recovery of the lost syngen (genetical species) is essential. Therefore, I carried out collection of natural strains in USA, Canada and Uruguay Republic.1. The collections were carried out at 197 points around the Five lakes and the eastern part of USA, and at 78 points in Uruguay Republic. P. caudatum was obtained from 34 sampling points, and 222 isolation lines were established.2. Three groups consisting in complementary mating types, that is "syngen", were discovered. These three syngens are independent from known syngens. They are tentatively called as syngen a, syngen b and syngen d. New strains belonging to syngen 1, syngen 3, syngen 5 and syngen 12 were also obtained.3. Surprisingly, a problem in identification of species revealed from the analyses of some strains, for example UC131 or UC151. They look like P. caudatum very much in size of cells and external morphology, but their RAPD patterns are quite different from many strains of P. caudatum. They have 2-5 vesicular type micronuclei, two contractile vacuoles and living in fresh water. These characteristics are not identical to the known biological species. Further studies are necessary whether they are really new biological species or not.4. Some strains show inter-syngen mating reactions. This evidence emphasizes an importance of establishment of the syngen standard strains.