Monterey Bay Aquarium Research Institute
Marine Botany

Ulva title imageLife History


A cross section of reproductive Ulva with reproductive cells swimming around it.

All of Ulva’s reproductive cells (swarmers) have flagella.  The gametes have two each, and the zoospores have four.  These flagella allow the little swarmers to move around and find each other and get to the sea floor.  Flagella in Ulva gametes are used for more than just motility.  Their cruciate flagellar root system (4-2-4-2) is elaborate.  The plasmalemma areas in both male and female gametes act as large, specialized mating structures that act in recognition and adhesion during mating.  The flagella also serve to increase surface area.  Presumably built into the flagellar apparatus are mechanisms for the cell to respond to light, chemicals and other cells.

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