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Freshwater Photosagnia split from its ancestor when populations along river deltas were regularly swept into fresher waters by the tides, causing selective pressure for thicker cell membranes and improved osmotic regulation. A trade-off of this was a loss of digestive function. When salinity or water decreases, such as when cells are washed ashore or into saltwater, a process is triggered that causes the cell to shrink into a spore, allowing long periods of dormancy (up to several months). These spores can be carried by water and high winds. Like its ancestor, it floats near the surface and can form large blooms.