Fig. 1

Intestinal microbiota alpha and beta diversity. A Boxplot representing the Shannon diversity index of all groups (n = 5). Boxes represent the interquartile range (IQR) between the first and third quartiles and the horizontal line inside the box defines the median. Whiskers represent the lowest and highest values within 1.5 times the IQR from the first and third quartiles. Samples with a relative abundance exceeding those values are represented as points outside the boxes. Different letters indicate significant differences among the groups (Kruskal–Wallis + Dunn’s post-test, P < 0.05). B NMDS ordination plot based on Bray-Curtis distance matrixes of normalized sample counts showing community differences among samples. Groups showing a clearer separation are control (C) and parasite exposed (R) fish in the winter (W) trial at the 10 weeks post-exposure (wpe) sampling (t3) and are highlighted with black borders in the plot. t1, t2, t3 stand for the different samplings performed at 2, 5 and 10 wpe, respectively. W and S stand for the different trials performed in winter and summer, respectively. C and R stand for control and parasite-exposed fish, respectively