Cytoplasmic streaming of calcium oxalate crystals in Callipsygma wilsonis (Bryopsidales, Chlorophyta)

Light microscopic study of the giant-celled, marine green alga Callipsygma wilsonis J. Agardh (Udoteaceae, Bryopsidales) revealed numerous birefringent crystalline inclusions in the terminal segments of the assimilatory axes. The inclusions were thin plates with a triangular shape in face view, a base up to 75 mm in length, and a height that was one-seventh the length of the base. Crystals of various sizes commonly were stacked face-to-face with one or more edges coinciding, but removal of organic material by treatment in sodium hypochlorite resulted in disaggregation. The crystals were soluble in dilute hydrochloric acid without effervescence but were insoluble in acetic acid. These diagnostic chemical solubility tests and a positive reaction to the Yasue staining reaction indicated that the crystals were composed of calcium oxalate. Scanning electron microscopy showed that most crystals had smoothly curving edges, but some had truncate or beveled margins. Calcium oxalate crystals have been reported to occur in the large central vacuoles of several bryopsidalean species, but the crystals in C. wilsonis were present in the parietal cytoplasm, which was evident from the presence of crystals in streaming cytoplasm. Calcium oxalate crystals, amyloplasts, chloroplasts, and other cytoplasmic constituents moved along cytoskeletal cables at rates of approximately 2.8 mm s-1. These findings add to a growing body of evidence that calcium oxalate crystals in diverse algae may be present in cellular compartments other than the central vacuole.