Abundance and diversity of lipid compounds in Exaiptasia diaphana is altered as a function of symbiotic state and life stage

Scleractinian corals engage in an endosymbiotic relationship with dinoflagellate algae to meet their nutritional demands in oligotrophic waters. Algae transfer photosynthetically-derived compounds to the host and host is structured to support and sustain the symbionts. The composition and abundance of these compounds as a function of host life stage and symbiotic state have yet to be described. Therefore, we aimed to characterize the effect of symbiosis and host life stage on the lipidomic profiles of the sea anemone Exaiptasia diaphana (commonly referred to as Aiptasia), a model system for the study of coral symbiosis. We sampled aposymbiotic and symbiotic Aiptasia adults, pedal lacerates, and larvae and isolated lipid fractions for liquid-chromatography mass-spectrometry (LC-MS) analysis. Over 200 lipid compounds were identified across all sample groups. There were more compounds in symbiotic than in aposymbiotic at every life stage. Lipidomic profiles separated based on both symbiotic state and life stage. Of the major lipids classes detected, triglycerides and ceramides were more abundant in symbiotic animals, phosphatidylcholines (PCs) were more abundant in pedal lacerates in both symbiotic states, and abundances of phosphatidylethanolamines (PEs) varied based on symbiotic state. Our results highlight the major influence of symbiotic state on lipid profiles in Aiptasia at different life stages and provide insight into how the lipidome changes in early life-stage cnidarians.