The Process of Chamber Formation in the Foraminifer Rosalina floridana (Cushman)
The Process of Chamber Formation in the Foraminifer Rosalina floridana (Cushman)
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有孔虫 Rosalina Florida (Cushman) 的腔室形成过程
DOI：
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发表时间：
1967
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影响因子：
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通讯作者：
R. W. Angell
中科院分区：
文献类型：
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作者：
R. W. Angell
概要。有孔虫Rosalina floridana建立了一个有室的石灰质测试，通过增加新的室定期扩大。R. floridana开始通过构建藻类生长囊肿来形成一个腔室，该囊肿覆盖动物的背侧并粘合到基底上。构建包囊的伪足结合形成细胞质模板或原基，室壁将在其上分泌。电子显微照片显示原基细胞质是一个几乎空泡的“泡沫”，其中含有线粒体、纤维状物质和电子致密颗粒。新腔室的有机衬里由伪足分泌到原基上，在有机衬里完成后，细胞质从测试中流入形成腔室，并迫使原基细胞质通过新的孔出来。这种“泡沫状”原基细胞质在测试的背表面上形成鞘;当它在适当的位置时，一层方解石沉积在新室的壁上和测试的其余部分上。当钙化完成时，鞘破裂，并随着有孔虫逐渐移出生长囊并开始正常进食而并入新形成的伪足。
在正常伪足和原基中产生囊泡状细胞质被认为是一种大大增加细胞质体积的方法，其结果是细胞质质量损失很小。在原基中，在产生有机衬里的过程中，泡状细胞质显然只作为伪足分泌膜的支持物，并可能不参与分泌过程。这些细胞质形成了钙化过程中出现的鞘。这种观点是先进的，虽然鞘可以在钙化过程中与囊泡内的线粒体积极运输钙到晶体生长的网站，其更可能的功能是形成一个分区之间的部分钙化和环境。然后，有孔虫可以从细胞质中的混合储备中分泌CaCO 3到鞘和室膜之间的区域。基底膜被认为是钙化过程中的成核剂，负责晶体的有序化，因此它们的C轴垂直于腔室的表面。
SYNOPSIS. The foraminifer Rosalina floridana builds a chambered, calcareous test which is periodically enlarged by the addition of new chambers. R. floridana begins to form a chamber by constructing an algal growth cyst which covers the dorsal side of the animal and is cemented to the substrate. The pseudopods that build the cyst coalesce to form a cytoplasmic template or anlage on which the chamber walls will be secreted. Electron micrographs reveal the anlage cytoplasm to be a “froth” of nearly empty vesicles which contain mitochondria, fibrillar material, and electron dense granules. The organic lining of the new chamber is secreted on the anlage by pseudopods extending thru it. After the organic lining is completed, cytoplasm from within the test flows into the forming chamber and forces the anlage cytoplasm out thru the new aperture. This “frothy” anlage cytoplasm forms a sheath over the dorsal surface of the test; while it is in place, a layer of calcite is deposited on the walls of the new chamber and over the rest of the test. When calcification is completed, the sheath breaks up and is incorporated into newly formed pseudopods as the foraminifer gradually moves out of the growth cyst and begins normal feeding.
The production of vesiculated cytoplasm in normal pseudopods and in the anlage is viewed as a method of greatly increasing cytoplasmic volume with a resultant very small loss in cytoplasmic mass. In the anlage during the production of the organic lining the vesiculated cytoplasm apparently acts only as a support for the membranes being secreted by the pseudopods and presumably does not take part in the secretory process. This same cytoplasm forms the sheath that is present during calcification. The view is advanced that, altho the sheath could be active during calcification with the mitochondria within the vesicles actively transporting calcium to sites of crystal growth, its more probable function is to form a partition between the parts to be calcified and the environment. The foraminifer could then secrete CaCO3 from pooled reserves in the cytoplasm into the area between the sheath and the chamber membranes. The basal membrane is considered the nucleating agent during calcification and is responsible for the ordering of the crystals so their C axes are perpendicular to the surface of the chamber.