THE EFFECT OF SYMBIONT COMPETITION ON HOST-SYMBIONT SPECIFICITY IN ANIMAL-ALGAL MUTUALISMS

Open Access
Author:
Winstead, Daniel
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Todd C. LaJeunesse, Thesis Supervisor
  • James H. Marden, Honors Advisor
Keywords:
  • Symbiodiniaceae
  • Cassiopea
  • mutualism
  • competition
  • Zooxanthellae
  • Host-symbiont specificity
  • Mutualism specificity
  • Cnidaria
Abstract:
The increased frequency of bleaching events along with declining populations of reef-building corals warrants the further study and understanding of Cnidarian-Symbiodiniaceae mutualisms. The species of Symbiodiniaceae that colonizes the host directly influences the fitness of coral, but the mechanism of this specificity is poorly understood. Here, we used the mangrove jellyfish (Cassiopea xamachana) as a model organism, to test if the concentration of Symbiodiniaceae spp. during polyp colonization positively correlates with the final concentration of Symbiodiniaceae spp. within the tissues of C. xamachana after strobilation. In this experiment, we inoculated C. xamachana with pairwise dilutions of three species of Symbiodiniaceae; the homologous symbiont Symbiodinium microadriaticum, and heterologous symbionts; Breviolum minutum and Durusdinium trenchii. Using qPCR, we found that the homologous symbiont S. microadriaticum was more abundant in ephyrae than the other two species when introduced at low concentrations. When ephyrae were inoculated by both heterologous Symbiodiniaceae spp., differences in final symbiont cell abundance were less pronounced. These data suggest that the relative amount of different Symbiodiniaceae spp. in the water column has dissimilar effects on host colonization, dependent on the symbiont species present during inoculation. Using this study as a baseline, future studies should focus on how host colonization changes with environmental stress in order to understand how this symbiont-host specificity may shift with continued warming of the oceans. However, despite the importance of physical environmental conditions on influencing the stability of certain host – symbiont combinations, species-specific fidelity between host and symbiont appear to be most important.