Meeting Abstract
Most mutualisms involving cnidarians and symbiotic dinoflagellates exhibit high specificity and partner stability. Whether this specificity and stability is conferred/regulated more by the host or symbiont remains largely unknown. The upside-down jellyfish, Cassiopea xamachana, is generally found to host Symbiodinium microadriaticum in nature. However under sterile laboratory conditions, this animal is capable of forming viable symbioses with a multitude of different Symbiodinium species. We took advantage of C. xamachana’s promiscuity under controlled experimental conditions to examine the outcome of symbiont competition within the host. Aposymbiotic polyps of Cassiopea xamachana polyps were exposed to various pairwise combinations of different species of Symbiodinium, with each symbiont introduced at equal and skewed cell proportions. The infected polyps were cultivated for 4-5 weeks until metamorphosis. Following strobilation, the relative abundances for each symbiont pairing were determined among individual juvenile jellyfish using qPCR. Large differences in infection dynamics were observed depending on the opposing Symbiodinium spp. used, indication that competition between symbionts dictates host-symbiont specificity in nature.
