Fish mucus metabolome reveals fish life-history traits
Résumé
Fish mucus has important biological and ecological
roles such as defense against fish pathogens and
chemical mediation among several species. A non-targeted
liquid chromatography–mass spectrometry metabolomic
approach was developed to study gill mucus of eight butterflyfish
species in Moorea (French Polynesia), and the
influence of several fish traits (geographic site and reef
habitat, species taxonomy, phylogeny, diet and parasitism
levels) on the metabolic variability was investigated. A
biphasic extraction yielding two fractions (polar and apolar)
was used. Fish diet (obligate corallivorous, facultative
corallivorous or omnivorous) arose as the main driver of
the metabolic differences in the gill mucus in both fractions,
accounting for 23% of the observed metabolic variability
in the apolar fraction and 13% in the polar fraction.
A partial least squares discriminant analysis allowed us to
identify the metabolites (variable important in projection,
VIP) driving the differences between fish with different
diets (obligate corallivores, facultative corallivores and
omnivorous). Using accurate mass data and fragmentation
data, we identified some of these VIP as glycerophosphocholines,
ceramides and fatty acids. Level of monogenean
gill parasites was the second most important factor shaping
the gill mucus metabolome, and it explained 10% of the
metabolic variability in the polar fraction and 5% in the
apolar fraction. A multiple regression tree revealed that the
metabolic variability due to parasitism in the polar fraction
was mainly due to differences between non-parasitized and
parasitized fish. Phylogeny and butterflyfish species were
factors contributing significantly to the metabolic variability
of the apolar fraction (10 and 3%, respectively) but
had a less pronounced effect in the polar fraction. Finally,
geographic site and reef habitat of butterflyfish species did
not influence the gill mucus metabolome of butterflyfishes.