Host and Symbiont Relationships

Abstract

The presence of algal associations with spinose planktonic foraminifera is one of the most obvious features of living individuals. Some species such as G. sacculifer, viewed with the unaided eye, appear distinctly tawny colored due to the abundance of dinoflagellates held within the rhizopodial system and sequestered in the intrashell cytoplasm. In the absence of algae, the cytoplasm is colorless or only faintly tinted amber, sometimes slightly reddish or greenish depending on the food they have consumed. The widespread occurrence of algal associations with planktonic foraminifera, especially the spinose species, suggests that this relationship is of profound significance in the physiology and perhaps phylogeny of the species.