| Abstract: | Algae injected into green hydra are taken up rapidly and in relatively large numbers, resulting in an increased symbiont population in digestive cells. The increase is temporary and the normal stock population size is restored within 24 hours after injection. Restoration of the normal population size is taken as evidence for regulation, and the technique offers a means for eliciting and studying at least one type of regulatory mechanism. Similarly, a method is described for rapid assay and visualization of digestive cell mitosis. This method may facilitate the investigation of other potential regulatory mechanisms which may involve interaction between host and algal cell division. Finally, symbiont overgrowth of host cells resulting from nutrient enrichment is described. The observations lend support to the hypothesis that nutrient limitation may regulate population size of algal symbionts. |
