The Triradiate and other Forms of Nitzschia Closterium (Ehrenberg) Wm. Smith, Forma Minutissima of Allen and Nelson
The Triradiate and other Forms of Nitzschia Closterium (Ehrenberg) Wm. Smith, Forma Minutissima of Allen and Nelson
复制标题
DOI：
10.1017/s002531540001211x
复制
发表时间：
1946-07
影响因子：
1.2
通讯作者：
D. P. Wilson
中科院分区：
文献类型：
--
作者：
D. P. Wilson
1.对最初由艾伦和纳尔逊（1910）从海洋中分离出来并在普利茅斯和其他地方生长的菱形藻种的自然历史进行了研究。结果表明，存在三种主要类型的细胞：正常的双臂（吻），三辐射状的三臂和椭圆形没有。正常细胞和三辐射细胞都通过分裂产生椭圆形，这样产生的椭圆形可以繁殖形成更多的椭圆形，或者可以长出两个或三个臂，通常是两个，以形成正常细胞或三辐射细胞。2.在良好的光照条件下比在弱光照下更容易产生椭圆。3.细胞壁的硅化程度很低，与大多数硅藻不同的是，细胞可以伸长而不形成孢子。连续传代培养的细胞大小的最大值和平均值是可变的。4.当三辐射体存在时，它们可能，而且在良好的培养条件下经常这样做，比正常细胞繁殖得更快，最后几乎完全控制了培养物。偶尔有一部分三辐状细胞缩短一条臂，并在连续的分裂过程中逐渐进入正常状态。这一过程在秋季发生的趋势比在任何其他时候都要大。1941年11月，普利茅斯和船体的几种培养物同时用这种方法大规模地生产出了法线，这是一个值得注意的例子。5.有证据表明，在不利的文化条件下，三辐射往往被淘汰。6.在几种培养物中偶尔会出现十字形细胞，但不可能获得它的纯培养物，因为这种类型似乎有些不稳定，很容易恢复到其他形式。然而，它已经持续了很长时间和很多代人。7.结果表明，三辐射型发生在自然界中，没有理由认为这是一个异常的形式，由于培养。8.命名进行了讨论，并已决定暂时保留名称艾伦和纳尔逊最初给它，虽然有一种可能性，这是一个单独的物种从新月菱形藻（EHR。W.史密斯
1. The natural history in culture of the species of Nitzschia originally isolated from the sea by Allen & Nelson (1910) and grown at Plymouth and elsewhere ever since has been studied. It is shown that three main types of cell exist: normal with two arms (rostra), triradiate with three arms and ovals with none. Both normals and triradiates produce ovals by division, and the ovals so produced can multiply to form further ovals, or can grow either two or three arms, generally two, to form normal or triradiate cells. 2. Ovals are more readily produced under good lighting conditions than under weak illumination. 3. The cell wall is very lightly silicified, and the cells, unlike those of most diatoms, can elongate without auxospore formation. The maximum, and with it apparently the average, cell size of successive subcultures is variable. 4. When triradiates are present they may, and frequently do under good cultural conditions, multiply faster than normal cells and finally may almost completely dominate the cultures. Now and again a proportion of the triradiate cells shorten one arm and gradually pass, during successive divisions, into the normal condition. There is a greater tendency for this process to take place in the autumn than at any other time. There was a notable instance in November 1941 when several cultures at Plymouth and at Hull simultaneously produced normals by this method on an extensive scale. 5. There is evidence that under unfavourable cultural conditions triradiates tend to be eliminated. 6. A cruciform type of cell has appeared occasionally in several cultures, but it has not been possible to obtain pure cultures of it, for the type appears to be somewhat unstable and readily reverts to the other forms. It has, however, persisted for a long time and for very many generations. 7. It is shown that the triradiate type occurs in nature, and there is no reason to suppose that it is an abnormal form due to culturing. 8. The nomenclature is discussed and it has been decided for the time being to retain the name Allen and Nelson originally gave to it, although there is a possibility that it is a species separate from Nitzschia closterium (Ehr.) W. Smith.