Symbiont-host relationships in chemosynthetic mussels: A comprehensive lipid biomarker study

► We provide a lipid-based view of chemosynthetic symbiosis in three mussel species from hot and cold seeps. ► We successfully identified IPLs as suitable marker for estimating the abundance of symbionts within a host organism. ► δ13C analysis of host and symbiont-specific lipids highlight the chemosynthetic carbon supply for the mussels. ► Compositional and δ13C variation point to distinct nutritional preferences/carbon metabolism for the respective symbiont.