69.4 Friday, Jan. 6 Mucilage Variation and Ultrastructure Among Symbiodinium Strains MAZZILLO MAYS, Maria*; KEMPF, Stephen C.; Auburn University; Auburn University email@example.com
Symbiodinium are unicellular dinoflagellates that reside intracellularly in a variety of invertebrate hosts, including cnidarians. In this symbiosis, the endosymbiotic algae are enclosed in a symbiosome membrane (host and symbiont-derived) and donate photosynthetically fixed carbon to the host in exchange for nutrients. Symbiodinium is a diverse genus of 9 clades with multiple strains in each clade. The specificity of the association between symbiont and host varies with some relationships being highly specific and others of a general nature. The symbiont secretes mucilage that lies at the interface with the host and may be involved in recognition and specificity. Cultured Symbiodinium from a variety of clades were labeled with 2 antibodies to symbiont mucilage (PC3, developed to a clade B alga cultured from Aiptasia pallida; BF10, developed to a clade F alga cultured from Briareum sp.). The labeling was visualized with a fluorescent marker and examined with epiflorescence and confocal microscopes. PC3 antigen was found in cultured Symbiodinium from clades A and B but not clades C, D, and F. Within clades A and B there was variation in the amount of label present. BF10 antigen was more specific and only found in strains closely related to the strain the antibody was created against. These results indicate that the mucilage secretions do vary amongst Symbiodinium strains. Since they are present at the host-symbiont interface, these variations in mucilage composition could house the differences in molecular structure that are involved in specificity. Examining the ultrastructure of the mucilage is also important in understanding how host/symbiont specificity comes about. Identifying how host and symbiont establish these specific associations at the cellular/molecular level will give insight into how these symbioses function.