Butterflyfish gill mucus metabolome reflects diet preferences and gill parasite intensities

Fish mucus is the main surface of exchange between fish and the environment and plays numerous biological and ecological roles such as protection and chemical mediation. In this study, we investigated the influence of phylogeny, reef habitat, diet, and gill parasitism levels on the gill mucus metabolome of butterflyfishes in Moorea (French Polynesia). Gill mucus was extracted using a biphasic extraction yielding two fractions (polar and apolar), which were analyzed by liquid-chromatography tandem mass spectrometry (LC-ESI-MS). Fish diet explained the highest metabolomic variability of both fractions, with parasitism being the second most important driver in the polar fraction. Ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-HRMS/MS) analyses allowed to putatively identify several glycerophosphocholines, ceramides, and fatty acids related to fish diet and the identification of several peptides specific to nonparasitized fish.