Pseudo-nitzschia Resting State
Most species in the genus Pseudo-nitzschia do not have a resting stage in their life cycle, but it is suspected that there are some that may experience this resting state. Resting spores are usually induced by factors in the diatom's external environment. The availability of nutrients like silicon and nitrogen, temperature, pH, and irradiance from the sunlight are all external factors that could induce the resting state of the diatom. The cytology behind resting spores in Pseudo-nitzschia has not been well studied.
Within the pennate diatoms, the resting spores are morphologically different cells from the vegetative cells. This may be compared to centric diatoms, particularly those that reside in environments that expose them to desiccation, whose vegetative cells directly become dormant. This morphological difference arises from the internal valves that are created inside of the cell wall of the vegetative cell. The two valves become much thicker and less porous while the girdle is less developed since the cell does not need to concern itself with division while in the resting state. These resting spores have stores of nutrients (especially in the form of oil) and are able to survive many years before germination under more favorable conditions.
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copyright Jennifer Shin 1999.