Observations on the micro-anatomy of crystallolithus hyalinus gaarder and markali

Summary

The fine structure of Crystallolithus hyalinus (Gaarder and Markali), known to be the motile stage of Coccolithus pelagicus (Wallich) Schiller (Parke and Adams 1960), has been investigated for purposes of comparison with Chrysochromulina and Prymnesium, recently recognised as probably related to it. Anoptral contrast light microscopy of living cells and electron microscopy of thin sections and shadow-cast whole mounts show that there is a close resemblance to species of Chrysochromulina not only in cell structure but also in the details of haptonema structure and scale structure. The origin of the scales from internal vesicles has been traced as in other genera but the holococcoliths (crystalloliths) do not appear to arise in this way. The mode of origin of the crystalloliths is thus unknown, but it is suggested that they may be developed outside the cell from calcite secreted in solution into the appropriate cavity. Their constant position between a layer of scales and an outer enveloping skin is consistent with this and one unfamiliar cytoplasmic organelle, composed of peculiar thick-walled tubes within some large superficial vesicles, is described as perhaps involved in this process. Apart from these special features the resemblance to both Chrysochromulina and Prymnesium is sufficient to add considerable weight to Christensen's suggestion (Christensen 1962) that a new group should be defined to accommodate these genera.