Meeting Abstract
21.2 Friday, Jan. 4 Evolutionary and ecological significance of sponge-Symbiodinium symbioses: genetic regulation of uptake and maintenance in sponges. HILL, M*; HILL, A; COTMAN, C; FRIDAY, S; HEIST, T; MCCAULEY, M; PETERSON, K; RICHARDSON, C; RIESGO, A; STREHLOW, B; Univ. of Richmond; Univ. of Richmond; Univ. of Richmond; Univ. of Richmondq; Univ. of Richmond; Univ. of Mississippi; Univ. of Richmond; Univ. of Virginia; CEAB, Spain; Univ. of Richmond mhill2@richmond.edu
Symbioses involving Symbiodinium are arguably the most important ecological interaction on coral reefs because zooxanthellae energetically subsidize the entire community. These algal symbionts also enhance rates of calcification, and thus facilitate the creation of three-dimensional structure for all organisms. Nonetheless, we have a remarkably limited understanding of the symbiont’s niche (e.g., why is zooxanthella distribution so restricted among sponge hosts?). We will present two novel hypotheses derived from our work with sponges (the Magnesium Inhibition Hypothesis and the Arrested Phagosome Hypothesis) that help explain well-known aspects of Symbiodinium associations regardless of taxonomic status of the host. We will argue that sponges afford unique methodological opportunities and broad-reaching insights into the associations found in all other Symbiodinium-based symbioses. We will present research examining the genetic regulation, physiological integration, and ecological/evolutionary significance of Symbiodinium symbioses involving sponge hosts. We will present data from suppressive subtractive hybridization and transcriptomic-based approaches that identify genes differentially regulated during zooxanthella uptake. Gene expression profiles will be correlated with various stages of reinfection as aposymbiotic sponge hosts re-acquire their algal partners. The physiological integration of partners and capacity of Clade G Symbiodinium to tolerate stressful conditions will be presented. Finally, we will evaluate in hospite “residence time” as a useful heuristic for studying zooxanthella symbioses.
