A preliminary account of the application of thin-sectioning, freeze-etching, and scanning electron microscopy to the study of coralline algae

Abstract

Preliminary studies of Corallina vancouveriensis Yendo and C. officinalis L. suggest that only the surface and immediately subsurface cells are intact, the majority of the cells at the apex having degenerate protoplasts. Scanning microscopy shows that the surface of the apical segment is reticulate, each space of the reticulum having a central pore. Thin sections indicate that the pore is, in fact, a relict pit connection in the inner tangential wall of the eroded surface cells, and the presence of this structure close to the apex suggests that erosion of the thallus surface is rapid. Thin sections at the apex also show that Golgi systems are well developed, producing numerous large vesicles, though other large vesicles may possibly result from degeneration of the endoplasimc reticulum. Replicas prepared by freeze-etching of fresh and fixed material show that large vesicles fuse directly with the calcareous wall region in Corallina and Calliarthron, some remaining intact within the wall matrix. Other vesicles discharge to form an amorphous inner wall region which presumably calcifies later. Cells of the genicula have a distinctive wall structure, and are almost devoid of content, though a few relict chloroplasts are present. Scanning microscopy suggests that species of Bossiella may be generally similar in surface development to Calliarthron and Corallina.