Meeting Abstract

P2.148  Wednesday, Jan. 5  Mucilage Variation Among Symbiodinium Strains MAZZILLO MAYS, Maria*; KEMPF, Stephen; Auburn University; Auburn University mazzimj@auburn.edu

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 8 clades with multiple strains in each clade. The specificity of the association between symbiont and host varies with some relationships being highly specific (one host with one algal strain) and others of a general nature (a generalist host or symbiont associating with several symbionts or hosts). The symbiont secretes mucilage that lies at the interface with the host as part of the symbiosome membrane. Cultured Symbiodinium from a variety of clades were labeled with one of 2 antibodies to symbiont mucilage (PC3, developed to a clade B alga cultured from Aiptasia pallida; BF10, developed to a clade C 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 and D. 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. Identifying how host and symbiont establish these specific associations at the cellular/molecular level will give insight into how these symbioses functions.