Meeting Abstract

P3.172  Tuesday, Jan. 6  How does the cell morphology of the sea anemone, Aiptasia pallida , change as a result of its symbiosis with intracellular zooxanthellae? HUSSAIN, F.N.*; MERZ, R.A.; VALLEN, E.A.; Swarthmore College; Swarthmore College; Swarthmore College fhussai1@swarthmore.edu

The ability of hermatypic corals and other anthozoa to host or expel intracellular symbiotic algae suggests substantial plasticity in cell architecture depending on the presence of the symbiont. To understand the impact of the symbiont on host cells involved in a symbiotic relationship, we studied the changes in cell morphology of sea anemones, Aiptasia pallida , in the presence or absence of symbiotic zooxanthellae. We hypothesize that anemones must manipulate their cell shape and cytoskeleton in order to accommodate zooxanthellae. We co-stained the nuclei and cytoplasmic f-actin of gastrodermal cells using OliGreen and fluorescently-labeled phalloidin, respectively. Through confocal microscopy, we observed that the size of gastrodermal cells increased dramatically as a result of the presence of intracellular zooxanthellae. Cross-sectional areas of symbiotic host cells were frequently up to five times greater than the area of aposymbiotic cells. Furthermore, there were distinct differences in the shapes of cells with and without zooxanthellae present. Symbiotic gastrodermal cells had rounded cell membranes that fit snugly over the algal cells, while aposymbiotic cells were more polygonal in shape. Future research, including staining of microtubules, may provide insight into how the cytoskeleton in symbiotic anemones accommodates zooxanthellae. Such knowledge may help explain the mechanisms by which the symbiosis is initiated, sustained, and terminated.