Cell sloughing in the littoral zone coralline alga, Spongites yendoi (Foslie) Chamberlain (Corallinales, Rhodophyta)

Abstract Spongites yendoi (Foslie) Chamberlain is an abundant non-geniculate coralline alga in the lower eulittoral zone along the south and west coast of South Africa, where it is associated primarily with the territorial, gardening limpet, Patella cochlear Born. In November 1990, June 1991 and November 1991, large patches of Spongites yendoi became white. Microscopic examination revealed that a surface layer was being shed, and that healthy living filaments were found below this sloughing layer. Unlike most corallines, which may shed an epithallial surface layer, S. yendoi was shedding from deep within the thallus, well below the layer of meristematic cells. A new layer of meristematic cells was regenerated below the layer which was being shed. The production of new sporangial conceptacles was observed at the same time. This type of cell sloughing could be a response to a physical phenomenon, a mechanism for preventing fouling, a means of discarding old conceptacles and grazer-damaged cells to prevent i...