Fig. 1.

Symbiosis specificity in Aiptasia adults. In each of three experiments, aposymbiotic adults from clonal anemone line CC7 were incubated for 31 days in the absence of algae or in the presence of one of four clonal, axenic Symbiodinium strains, as indicated (see Materials and methods; 15 animals per treatment in each experiment). (A) At intervals, four randomly chosen anemones per treatment were photographed with the stereomicroscope using white light (Anemone) or a GFP filter set (to visualize the chlorophyll autofluorescence of any Symbiodinium present: Algae). Representative images are shown. (B) Quantification of Symbiodinium populations at day 31. In each experiment, all 15 animals for each treatment were pooled and homogenized. Algal number and total protein were then determined by Guava flow cytometry and the BCA assay (see Materials and methods). Means ± s.e.m. (N=3). Separately, two individual CC7 animals stably populated with their endogenous algae were homogenized and analyzed in the same way, yielding 3122 and 2959 algal cells μg⁻¹ protein.