The Test Structure and Composition of the Foraminifer Rosalina floridana*

Abstract

SYNOPSIS. The composition of the test of Rosalina floridana (Cushman) was examined histochemically, and its structure was studied with the electron microscope by means of thin sections and carbon replicas. The test is composed of a thick organic lining overlain by one or more calcite layers bounded above and below by thin membranes. The membranes are fused to organic pore processes composed of coarse fibers that penetrate the calcite layers. The ***lining, consisting of coarse fibers matted into a laminated sheet, is considered a strengthening element of the test. The membranes covering each calcite layer are composed of fine, headed fibrils which in aggregate have a striated pattern; they are thought to be the crystal‐nucleating agent during calcification and to form a protective covering for the previously deposited calcite layers. The pore processes, which are devoid of an internal entrance for cytoplasm, are considered to be points of attachment for the membranes; they tie the organic test components into a unified whole. The calcite layers and the chambers lack this unity, being separated from each other and from the preceding chambers by membranes so that there are no calcite‐to‐calcite boundaries between them. An organic, sievelike structure of undetermined function has been found in the foramina of chambers near the prolocular region of the test. Histochemical methods show that the lining contains proteins, polysaccharides, and unidentified substances; the membranes and the pore processes stain as a protein‐polysaccharide complex free of other substances.

The ultrastructure of a planktonic foraminifer, Globigerinoides sacculifer (Brady), and its symbiotic dinoflagellates

“…Much research has been performed on the cytology and life history of benthic foraminifera (Schaudinn, 1895;Lister, 1903;Myers, 1935;Le Calvez, 1938, 1950Jepps, 1942;Grell, 1957;Hedley and Bertaud, 1962;Angell, 1967Angell, , 1971Lengsfeld, 1969a, b, c), but only a few cytological studies on planktonic foraminifera exist. Rhumbler (191 1) examined the test and cytoplasm of a wide variety of planktonic species.…”

Calcification acidifies the microenvironment of a benthic foraminifer (Ammonia sp.)

“…CaCO 3 precipitation is catalyzed on the surface of an organic template termed primary organic sheet (POS), being formed after establishment of the DBS (reviewed in Erez, 2003;Goldstein, 1999). In benthic rotalid foraminifera calcite wall thickening proceeds in two layers, termed 'primary calcite' on the POS of the newly forming chamber and a secondary layer termed 'secondary calcite' ( (Angell, 1967), reviewed in Erez, 2003;Hansen, 1999). This secondary calcite is excreted over the complete shell surface of the foraminifera during chamber formation, resulting in a fine lamination of older chambers (Hansen, 1999).…”

Some Techniques and Applications of Scanning Electron Microscopy in the Fields of Marine Science

“…Figure 2 shows, at a higher magnification, representative pores on the outer surface of the test proper; these pores are, on the average, 3-5,1* in diameter, depending on the particular chamber on which the pores are located. This photograph illustrates the calcite layering of the test, showing three welldefined layers; similar evidence is given in transmission electron micrographs of Rosalina floridana (Angell, 1967). Figure 3 illustrates the embossed float chamber pores.…”