Studies on the species evolution in Paramecium caudatum

为了研究尾草履虫的物种进化，需要许多不同地理位置的自然菌株，并通过恢复失去的同根（遗传种）来建立物种。因此，我在美国、加拿大和乌拉圭共和国开展了天然菌株的收集工作。收集工作在五大湖和美国东部的197个地点进行，在乌拉圭共和国的78个地点进行。从34个采样点获得尾尾假单胞菌，建立222个分离株。发现了三个由互补交配类型组成的群体，即“syngen”。这三个合原是独立于已知的合原的。它们暂定为syngen a、syngen b和syngen d，并获得了属于syngen 1、syngen 3、syngen 5和syngen 12的新菌株。令人惊讶的是，从一些菌株的分析中发现了物种识别的问题，例如UC131或UC151。它们在细胞大小和外部形态上与尾尾草非常相似，但它们的RAPD模式与尾尾草的许多品系有很大的不同。它们有2-5个囊泡型微核，2个可收缩的液泡，生活在淡水中。这些特征与已知的生物物种并不相同。它们是否真的是新的生物物种，还需要进一步研究。有些菌株表现出同属间交配反应。这一证据强调了建立同源标准菌株的重要性。

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.